Gene Summary

Gene:PRKCSH; protein kinase C substrate 80K-H
Aliases: GIIB, PCLD, PLD1, G19P1, PCLD1, PKCSH, AGE-R2, VASAP-60
Summary:This gene encodes the beta-subunit of glucosidase II, an N-linked glycan-processing enzyme in the endoplasmic reticulum. The encoded protein is an acidic phosphoprotein known to be a substrate for protein kinase C. Mutations in this gene have been associated with the autosomal dominant polycystic liver disease. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jan 2014]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:glucosidase 2 subunit beta
Source:NCBIAccessed: 11 March, 2017


What does this gene/protein do?
Show (11)

Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 12 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Transfection
  • Signal Transduction
  • Polymorphism
  • Wnt Proteins
  • Molecular Sequence Data
  • Genotype
  • Intracellular Signaling Peptides and Proteins
  • X-Ray Computed Tomography
  • Endoplasmic Reticulum
  • alpha-Glucosidases
  • Ultrasonography
  • Sequence Homology
  • Antineoplastic Agents
  • Amino Acid Sequence
  • DNA Mutational Analysis
  • Phosphoproteins
  • Newborns
  • Heterozygote
  • Loss of Heterozygosity
  • Mutation
  • Base Sequence
  • Somatostatin
  • Membrane Proteins
  • Cysts
  • Pedigree
  • Cell Surface Receptors
  • Liver Diseases
  • Chromosome 19
  • Chromosome Mapping
  • Glucosidases
  • Young Adult
  • Phenotype
  • Cohort Studies
  • TRPP Cation Channels
  • DNA Sequence Analysis
  • Polycystic Kidney, Autosomal Dominant
  • Genetic Predisposition
  • Single Nucleotide Polymorphism
  • Trinucleotide Repeats
Tag cloud generated 11 March, 2017 using data from PubMed, MeSH and CancerIndex

Latest Publications: PRKCSH (cancer-related)

Maeda T, Yuzawa S, Suzuki A, et al.
RhoA mediates the expression of acidic extracellular pH-induced matrix metalloproteinase-9 mRNA through phospholipase D1 in mouse metastatic B16-BL6 melanoma cells.
Int J Oncol. 2016; 48(3):1251-7 [PubMed] Related Publications
Solid tumors are characterized by acidic extracellular pH (pHe). The present study examined the contribution of small GTP-binding proteins to phospholipase D (PLD) activation of acidic pHe-induced matrix metalloproteinase-9 (MMP-9) production. Acidic pHe-induced MMP-9 production was reduced by C3 exoenzyme, which inhibits the Rho family of GTPases; cytochalasin D, which inhibits actin reorganization; and simvastatin, which inhibits geranylgeranylation of Rho. Small interfering RNA (siRNA) against RhoA, but not against Rac1 or Cdc42, significantly inhibited acidic pHe induction of MMP-9. Pull-down assays showed that acidic pHe increased the activated form of RhoA. Forced expression of constitutively active RhoA induced MMP-9 production, even at neutral pHe. RhoA siRNA also reduced acidic pHe induced PLD activity. Specific inhibition of PLD1 and Pld1 gene knockout significantly reduced acidic pHe-induced MMP-9 expression. In contrast, PLD2 inhibition or knockout had no effect on MMP-9 expression. These findings suggested that RhoA-PLD1 signaling is involved in acidic pHe induction of MMP-9.

Fite K, Gomez-Cambronero J
Down-regulation of MicroRNAs (MiRs) 203, 887, 3619 and 182 Prevents Vimentin-triggered, Phospholipase D (PLD)-mediated Cancer Cell Invasion.
J Biol Chem. 2016; 291(2):719-30 [PubMed] Free Access to Full Article Related Publications
Breast cancer is a leading cause of morbidity and mortality among women. Metastasis is initiated after epithelial-mesenchymal-transition (EMT). We have found a connection between EMT markers and the expression of four microRNAs (miRs) mediated by the signaling enzyme phospholipase D (PLD). Low aggressive MCF-7 breast cancer cells have low endogenous PLD enzymatic activity and cell invasion, concomitant with high expression of miR-203, -887, and -3619 (that decrease PLD2 translation and a luciferase reporter) and miR-182 (targeting PLD1) that are, therefore, "tumor-suppressor-like" miRs. The combination miR-887+miR-3619 abolished >90% of PLD enzymatic activity. Conversely, post-EMT MDA-MB-231 cells have low miR expression, high levels of PLD1/2, and high aggressiveness. The latter was reversed by ectopically transfecting the miRs, which was negated by silencing miRs with specific siRNAs. We determined that the molecular mechanism is that E-cadherin triggers expression of the miRs in pre-EMT cells, whereas vimentin dampens expression of the miRs in post-EMT invasive cells. This novel work identifies for the first time a set of miRs that are activated by a major pre-EMT marker and deactivated by a post-EMT marker, boosting the transition from low invasion to high invasion, as mediated by the key phospholipid metabolism enzyme PLD.

Zhang J, Bian Z, Zhou J, et al.
MicroRNA-638 inhibits cell proliferation by targeting phospholipase D1 in human gastric carcinoma.
Protein Cell. 2015; 6(9):680-8 [PubMed] Free Access to Full Article Related Publications
MicroRNAs (miRNAs) are a type of small non-coding RNAs that are often play important roles in carcinogenesis, but the carcinogenic mechanism of miRNAs is still unclear. This study will investigate the function and the mechanism of miR-638 in carcinoma (GC). The expression of miR-638 in GC and the DNA copy number of miR-638 were detected by real-time PCR. The effect of miR-638 on cell proliferation was measured by counting kit-8 assay. Different assays, including bioinformatics algorithms (TargetScan and miRanda), luciferase report assay and Western blotting, were used to identify the target gene of miR-638 in GC. The expression of miR-638 target gene in clinical CRC tissues was also validated by immunohistochemical assay. From this research, we found that miR-638 was downregulated in GC tissues compared with corresponding noncancerous tissues (NCTs), and the DNA copy number of miR-638 was lower in GC than NCTs, which may induce the corresponding downregulation of miR-638 in GC. Ectopic expression of miR-638 inhibited GC cell growth in vitro. Subsequently, we identified that PLD1 is the target gene of miR-638 in GC, and silencing PLD1 expression phenocopied the inhibitory effect of miR-638 on GC cell proliferation. Furthermore, we observed that PLD1 was overexpressed in GC tissues, and high expression of PLD1 in GC predicted poor overall survival. In summary, we revealed that miR-638 functions as a tumor suppressor in GC through inhibiting PLD1.

Kang DW, Choi CY, Cho YH, et al.
Targeting phospholipase D1 attenuates intestinal tumorigenesis by controlling β-catenin signaling in cancer-initiating cells.
J Exp Med. 2015; 212(8):1219-37 [PubMed] Free Access to Full Article Related Publications
Expression of the Wnt target gene phospholipase D1 (PLD1) is up-regulated in various carcinomas, including colorectal cancer (CRC). However, the mechanistic significance of its elevated expression in intestinal tumorigenesis remains unknown. In this study, we show that genetic and pharmacological targeting of PLD1 disrupts spontaneous and colitis-associated intestinal tumorigenesis in Apc(Min/+) and azoxymethane/dextran sodium sulfate mice models. Intestinal epithelial cell-specific PLD1 overexpression in Apc(Min/+) mice accelerated tumorigenesis with increased proliferation and nuclear β-catenin levels compared with Apc(Min/+) mice. Moreover, PLD1 inactivation suppressed the self-renewal capacity of colon cancer-initiating cells (CC-ICs) by decreasing expression of β-catenin via E2F1-induced microRNA (miR)-4496 up-regulation. Ultimately, low expression of PLD1 coupled with a low level of CC-IC markers was predictive of a good prognosis in CRC patients, suggesting in vivo relevance. Collectively, our data reveal that PLD1 has a crucial role in intestinal tumorigenesis via its modulation of the E2F1-miR-4496-β-catenin signaling pathway. Modulation of PLD1 expression and activity represents a promising therapeutic strategy for the treatment of intestinal tumorigenesis.

Jin S, Cui K, Sun ZQ, et al.
Screening analysis of candidate gene mutations in a kindred with polycystic liver disease.
World J Gastroenterol. 2015; 21(8):2343-51 [PubMed] Free Access to Full Article Related Publications
AIM: To find potential mutable sites by detecting mutations of the candidate gene in a kindred with polycystic liver disease (PCLD).
METHODS: First, we chose a kindred with PCLD and obtained five venous blood samples of this kindred after the family members signed the informed consent form. In the kindred two cases were diagnosed with PCLD, and the left three cases were normal individuals. All the blood samples were preserved at -85 °C. Second, we extracted the genomic DNA from the venous blood samples of the kindred using a QIAamp DNA Mini Kit and then performed long-range polymerase chain reaction (PCR) with different primers. The exons of PKD1 were all sequenced with the forward and reverse primers to ensure the accuracy of the results. Next, we purified the PCR products and directly sequenced them using Big Dye Terminator Chemistry version 3.1. The sequencing reaction was conducted with BiomekFX (Beckman). Finally, we analyzed the results.
RESULTS: A total of 42 normal exons were identified in detecting mutations of the PKD1 gene. A synonymous mutation occurred in exon 5. The mutation was a homozygous T in the proband and was C in the reference sequence. This mutation was located in the third codon and did not change the amino acid encoded by the codon. Missense mutations occurred in exons 11 and 35. These mutations were located in the second codon; they changed the amino acid sequence and existed in the dbSNP library. A nonsense mutation occurred in exon 15. The mutation was a heterozygous CT in the proband and was C in the reference sequence. This mutation was located in the first codon and resulted in a termination codon. This mutation had an obvious influence on the encoded protein and changed the length of the protein from 4303 to 2246 amino acids. This was a new mutation that was not present in the dbSNP library.
CONCLUSION: The nonsense mutation of exon 15 existed in the proband and in the third individual. Additionally, the proband was heterozygous for this mutation, so the mutable site was a pathogenic mutation.

Sudo M, Mori S, Madan V, et al.
Short-hairpin RNA library: identification of therapeutic partners for gefitinib-resistant non-small cell lung cancer.
Oncotarget. 2015; 6(2):814-24 [PubMed] Free Access to Full Article Related Publications
Somatic mutations of the epidermal growth factor receptor often cause resistance to therapy with tyrosine kinase inhibitor in non-small cell lung cancer (NSCLC). In this study, we aimed to identify partner drugs and pathways that can induce cell death in combination with gefitinib in NSCLC cells. We undertook a genome-wide RNAi screen to identify synthetic lethality with gefitinib in tyrosine kinase inhibitor resistant cells. The screening data were utilized in different approaches. Firstly, we identified PRKCSH as a candidate gene, silencing of which induces apoptosis of NSCLC cells treated with gefitinib. Next, in an in silico gene signature pathway analysis of shRNA library data, a strong correlation of genes involved in the CD27 signaling cascade was observed. We showed that the combination of dasatinib (NF-κB pathway inhibitor) with gefitinib synergistically inhibited the growth of NSCLC cells. Lastly, utilizing the Connectivity Map, thioridazine was identified as a top pharmaceutical perturbagen. In our experiments, it synergized with gefitinib to reduce p-Akt levels and to induce apoptosis in NSCLC cells. Taken together, a pooled short-hairpin library screen identified several potential pathways and drugs that can be therapeutic targets for gefitinib resistant NSCLC.

Han S, Huh J, Kim W, et al.
Phospholipase D activates HIF-1-VEGF pathway via phosphatidic acid.
Exp Mol Med. 2014; 46:e126 [PubMed] Free Access to Full Article Related Publications
Growth factor-stimulated phospholipase D (PLD) catalyzes the hydrolysis of phosphatidylcholine (PC), generating phosphatidic acid (PA) which may act as a second messenger during cell proliferation and survival. Therefore, PLD is believed to play an important role in tumorigenesis. In this study, a potential mechanism for PLD-mediated tumorigenesis was explored. Ectopic expression of PLD1 or PLD2 in human glioma U87 cells increased the expression of hypoxia-inducible factor-1α (HIF-1α) protein. PLD-induced HIF-1 activation led to the secretion of vascular endothelial growth factor (VEGF), a HIF-1 target gene involved in tumorigenesis. PLD induction of HIF-1α was significantly attenuated by 1-butanol which blocks PA production by PLD, and PA per se was able to elevate HIF-1α protein level. Inhibition of mTOR, a PA-responsive kinase, reduced the levels of HIF-1α and VEGF in PLD-overexpressed cells. Epidermal growth factor activated PLD and increased the levels of HIF-1α and VEGF in U87 cells. A specific PLD inhibitor abolished expression of HIF-1α and secretion of VEGF. PLD may utilize HIF-1-VEGF pathway for PLD-mediated tumor cell proliferation and survival.

Cnossen WR, Drenth JP
Polycystic liver disease: an overview of pathogenesis, clinical manifestations and management.
Orphanet J Rare Dis. 2014; 9:69 [PubMed] Free Access to Full Article Related Publications
Polycystic liver disease (PLD) is the result of embryonic ductal plate malformation of the intrahepatic biliary tree. The phenotype consists of numerous cysts spread throughout the liver parenchyma. Cystic bile duct malformations originating from the peripheral biliary tree are called Von Meyenburg complexes (VMC). In these patients embryonic remnants develop into small hepatic cysts and usually remain silent during life. Symptomatic PLD occurs mainly in the context of isolated polycystic liver disease (PCLD) and autosomal dominant polycystic kidney disease (ADPKD). In advanced stages, PCLD and ADPKD patients have massively enlarged livers which cause a spectrum of clinical features and complications. Major complaints include abdominal pain, abdominal distension and atypical symptoms because of voluminous cysts resulting in compression of adjacent tissue or failure of the affected organ. Renal failure due to polycystic kidneys and non-renal extra-hepatic features are common in ADPKD in contrast to VMC and PCLD. In general, liver function remains prolonged preserved in PLD. Ultrasonography is the first instrument to assess liver phenotype. Indeed, PCLD and ADPKD diagnostic criteria rely on detection of hepatorenal cystogenesis, and secondly a positive family history compatible with an autosomal dominant inheritance pattern. Ambiguous imaging or screening may be assisted by genetic counseling and molecular diagnostics. Screening mutations of the genes causing PCLD (PRKCSH and SEC63) or ADPKD (PKD1 and PKD2) confirm the clinical diagnosis. Genetic studies showed that accumulation of somatic hits in cyst epithelium determine the rate-limiting step for cyst formation. Management of adult PLD is based on liver phenotype, severity of clinical features and quality of life. Conservative treatment is recommended for the majority of PLD patients. The primary aim is to halt cyst growth to allow abdominal decompression and ameliorate symptoms. Invasive procedures are required in a selective patient group with advanced PCLD, ADPKD or liver failure. Pharmacological therapy by somatostatin analogues lead to beneficial outcome of PLD in terms of symptom relief and liver volume reduction.

Shin GC, Ahn SH, Choi HS, et al.
Hepatocystin contributes to interferon-mediated antiviral response to hepatitis B virus by regulating hepatocyte nuclear factor 4α.
Biochim Biophys Acta. 2014; 1842(9):1648-57 [PubMed] Related Publications
Hepatocystin/80K-H is known as a causative gene for autosomal dominant polycystic liver disease. However, the role of hepatocystin in hepatitis B virus-related liver disease remains unknown. Here, we investigated the role of hepatocystin on the cytokine-mediated antiviral response against hepatitis B virus infection. We investigated the antiviral effect and mechanism of hepatocystin by ectopic expression and RNAi knockdown in cell culture and mouse livers. Hepatocystin suppressed the replication of hepatitis B virus both in vitro and in vivo. This inhibitory effect was HBx-independent and mediated by the transcriptional regulation of viral genome via the activation of exogenous signal-regulated kinase 1/2 and the reduced expression of hepatocyte nuclear factor 4α, a transcription factor essential for hepatitis B virus replication. The amino-terminal region of hepatocystin was essential for regulation of this antiviral signaling pathway. We also found that hepatocystin acts as a critical component in interferon-mediated mitogen-activated protein kinase signaling pathway, and the interferon-induced antiviral activity against hepatitis B virus is associated with the expression levels of hepatocystin. We demonstrated that hepatocystin plays a critical role in modulating the susceptibility of hepatitis B virus to interferon, suggesting that the modulation of hepatocystin expression is important for cytokine-mediated viral clearance during hepatitis B virus infection.

Cnossen WR, te Morsche RH, Hoischen A, et al.
Whole-exome sequencing reveals LRP5 mutations and canonical Wnt signaling associated with hepatic cystogenesis.
Proc Natl Acad Sci U S A. 2014; 111(14):5343-8 [PubMed] Free Access to Full Article Related Publications
Polycystic livers are seen in the rare inherited disorder isolated polycystic liver disease (PCLD) and are recognized as the most common extrarenal manifestation in autosomal dominant polycystic kidney disease. Hepatic cystogenesis is characterized by progressive proliferation of cholangiocytes, ultimately causing hepatomegaly. Genetically, polycystic liver disease is a heterogeneous disorder with incomplete penetrance and caused by mutations in PRKCSH, SEC63, PKD1, or PKD2. Genome-wide SNP typing and Sanger sequencing revealed no pathogenic variants in hitherto genes in an extended PCLD family. We performed whole-exome sequencing of DNA samples from two members. A heterozygous variant c.3562C > T located at a highly conserved amino acid position (p.R1188W) in the low density lipoprotein receptor-related protein 5 (LRP5) gene segregated with the disease (logarithm of odds score, 4.62) but was not observed in more than 1,000 unaffected individuals. Screening of LRP5 in a PCLD cohort identified three additional mutations in three unrelated families with polycystic livers (p.V454M, p.R1529S, and p.D1551N), again all undetected in controls. All variants were predicted to be damaging with profound structural effects on LRP5 protein domains. Liver cyst tissue and normal hepatic tissue samples from patients and controls showed abundant LRP5 expression by immunohistochemistry. Functional activity analyses indicated that mutant LRP5 led to reduced wingless signal activation. In conclusion, we demonstrate that germ-line LRP5 missense mutations are associated with hepatic cystogenesis. The findings presented in this study link the pathophysiology of PCLD to deregulation of the canonical wingless signaling pathway.

Urribarri AD, Munoz-Garrido P, Perugorria MJ, et al.
Inhibition of metalloprotease hyperactivity in cystic cholangiocytes halts the development of polycystic liver diseases.
Gut. 2014; 63(10):1658-67 [PubMed] Free Access to Full Article Related Publications
OBJECTIVE: Polycystic liver diseases (PCLDs) are genetic disorders characterised by progressive bile duct dilatation and/or cyst development. Their pathogenesis is a consequence of hyperproliferation, hypersecretion and microRNA alterations in cholangiocytes. Here we evaluate the role of matrix metalloproteases (MMPs) in the hepatic cystogenesis of PCLDs.
DESIGN: Metalloprotease activity was measured by microfluorimetric assays in normal and polycystic cholangiocyte cultures from humans and rats, and gene expression by real time quantitative PCR. The role of cytokines, oestrogens and growth factors present in the cystic fluid of PCLD patients was evaluated for MMP activity. The MMP inhibitor marimastat was examined for cystic expansion in vitro and in polycystic kidney (PCK) rats.
RESULTS: Polycystic human and rat cholangiocytes displayed increased MMP activity, which was associated with increased mRNA levels of different MMPs. Interleukin (IL)-6 and IL-8, and 17β-oestradiol, all stimulated MMP activity in human cholangiocytes. The presence of antibodies against IL-6 and/or IL-8 receptor/s inhibited baseline MMP hyperactivity of polycystic human cholangiocytes but had no effect on normal human cholangiocytes. MMP-3 was overexpressed in cystic cholangiocytes from PCLD human and PCK rat livers by immunohistochemistry. Marimastat reduced MMP hyperactivity of polycystic human and rat cholangiocytes and blocked the cystic expansion of PCK cholangiocytes cultured in three-dimensions. Chronic treatment of 8-week-old PCK rats with marimastat inhibited hepatic cystogenesis and fibrosis.
CONCLUSIONS: PCLDs are associated with cholangiocyte MMP hyperactivity resulting from autocrine/paracrine stimulation by IL-6 and IL-8. Inhibition of this MMP hyperactivity with marimastat decreased hepatic cystogenesis in vitro and in an animal model of PCLD, offering a potential therapeutic tool.

Xu CZ, Shi RJ, Chen D, et al.
Potential biomarkers for paclitaxel sensitivity in hypopharynx cancer cell.
Int J Clin Exp Pathol. 2013; 6(12):2745-56 [PubMed] Free Access to Full Article Related Publications
Paclitaxel has been proved to be active in treatment and larynx preservation of HNSCC, however, the fact that about 20-40% patients do not respond to paclitaxel makes it urgent to figure out the biomarkers for paclitaxel-based treatment in Hypopharynx cancer (HPC) patients to improve the therapy effect. In this work, Fadu cells, treated or untreated with low dose of paclitaxel for 24 h, were applied to DNA microarray chips. The differential expression in mRNAs and miRs was analyzed and the network between expression-altered mRNAs and miRs was constructed. Differentially expressed genes were mainly enriched in superpathway of cholesterol biosynthesis (ACAT2, MSMO1, LSS, FDFT1 and FDPS etc.), complement system (C3, C1R, C1S, CFR and CFB etc.), interferon signaling (IFIT1, IFIT3, IFITM1 and MX1 etc.), mTOR signaling (MRAS, PRKAA2, PLD1, RND3 and EIF4A1 etc.) and IGF1 signaling (MRAS, IGFBP7, JUN and FOS etc.), most of these pathways are implicated in tumorigenesis or chemotherapy resistance. The first three pathways were predicted to be suppressed, while the last two pathways were predicted to be induced by paclitaxel, suggesting the combination therapy with mTOR inhibition and paclitaxel might be better than single one. The dramatically expression-altered miRs were miR-112, miR-7, miR-1304, miR-222*, miR-29b-1* (these five miRs were upregulated) and miR-210 (downregulated). The 26 putative target genes mediated by the 6 miRs were figured out and the miR-gene network was constructed. Furthermore, immunoblotting assay showed that ERK signaling in Fadu cells was active by low dose of paclitaxel but repressed by high dose of paclitaxel. Collectively, our data would provide potential biomarkers and therapeutic targets for paclitaxel-based therapy in HPC patients.

Park MH, Kang DW, Jung Y, et al.
Caffeic acid phenethyl ester downregulates phospholipase D1 via direct binding and inhibition of NFκB transactivation.
Biochem Biophys Res Commun. 2013; 442(1-2):1-7 [PubMed] Related Publications
Upregulation of phospholipase D (PLD) is functionally linked with oncogenic signals and tumorigenesis. Caffeic acid phenethyl ester (CAPE) is an active compound of propolis extract that exhibits anti-proliferative, anti-inflammatory, anti-oxidant, and antineoplastic properties. In this study, we demonstrated that CAPE suppressed the expression of PLD1 at the transcriptional level via inhibition of binding of NFκB to PLD1 promoter. Moreover, CAPE, but not its analogs, bound to a Cys837 residue of PLD1 and inhibited enzymatic activity of PLD. CAPE also decreased activation of matrix metalloproteinases-2 induced by phosphatidic acid, a product of PLD activity. Ultimately, CAPE-induced downregulation of PLD1 suppressed invasion and proliferation of glioma cells. Taken together, the results of this study indicate that CAPE might contribute to anti-neoplastic effect by targeting PLD1.

Cipriano R, Bryson BL, Miskimen KL, et al.
Hyperactivation of EGFR and downstream effector phospholipase D1 by oncogenic FAM83B.
Oncogene. 2014; 33(25):3298-306 [PubMed] Free Access to Full Article Related Publications
Despite the progress made in targeted anticancer therapies in recent years, challenges remain. The identification of new potential targets will ensure that the arsenal of cancer therapies continues to expand. FAM83B was recently discovered in a forward genetic screen for novel oncogenes that drive human mammary epithelial cell (HMEC) transformation. We report here that elevated FAM83B expression increases Phospholipase D (PLD) activity, and that suppression of PLD1 activity prevents FAM83B-mediated transformation. The increased PLD activity is engaged by hyperactivation of epidermal growth factor receptor (EGFR), which is regulated by an interaction involving FAM83B and EGFR. Preventing the FAM83B/EGFR interaction by site-directed mutation of lysine 230 of FAM83B suppressed PLD activity and MAPK signaling. Furthermore, ablation of FAM83B expression from breast cancer cells inhibited EGFR phosphorylation and suppressed cell proliferation. We propose that understanding the mechanism of FAM83B-mediated transformation will provide a foundation for future therapies aimed at targeting its function as an intermediary in EGFR, MAPK and mTOR activation.

Tietz Bogert PS, Huang BQ, Gradilone SA, et al.
The zebrafish as a model to study polycystic liver disease.
Zebrafish. 2013; 10(2):211-7 [PubMed] Free Access to Full Article Related Publications
In the polycystic liver diseases (PLD), genetic defects initiate the formation of cysts in the liver and kidney. In rodent models of PLD (i.e., the PCK rat and Pkd2(WS25/-) mouse), we have studied hepatorenal cystic disease and therapeutic approaches. In this study, we employed zebrafish injected with morpholinos against genes involved in the PLD, including sec63, prkcsh, and pkd1a. We calculated the liver cystic area, and based on our rodent studies, we exposed the embryos to pasireotide [1 μM] or vitamin K3 [100 μM] and assessed the endoplasmic reticulum (ER) in cholangiocytes in embryos treated with 4-phenylbutyrate (4-PBA). Our results show that (a) morpholinos against sec63, prkcsh, and pkd1a eliminate expression of the respective proteins; (b) phenotypic body changes included curved tail and the formation of hepatic cysts in zebrafish larvae; (c) exposure of embryos to pasireotide inhibited hepatic cystogenesis in the zebrafish models; and (d) exposure of embryos to 4-PBA resulted in the ER in cholangiocytes resolving from a curved to a smooth appearance. Our results suggest that the zebrafish model of PLD may provide a means to screen drugs that could inhibit hepatic cystogenesis.

Tazat K, Harsat M, Goldshmid-Shagal A, et al.
Dual effects of Ral-activated pathways on p27 localization and TGF-β signaling.
Mol Biol Cell. 2013; 24(11):1812-24 [PubMed] Free Access to Full Article Related Publications
Constitutive activation or overactivation of Ras signaling pathways contributes to epithelial tumorigenesis in several ways, one of which is cytoplasmic mislocalization of the cyclin-dependent kinase inhibitor p27(Kip1) (p27). We previously showed that such an effect can be mediated by activation of the Ral-GEF pathway by oncogenic N-Ras. However, the mechanism(s) leading to p27 cytoplasmic accumulation downstream of activated Ral remained unknown. Here, we report a dual regulation of p27 cellular localization by Ral downstream pathways, based on opposing effects via the Ral effectors RalBP1 and phospholipase D1 (PLD1). Because RalA and RalB are equally effective in mislocalizing both murine and human p27, we focus on RalA and murine p27, which lacks the Thr-157 phosphorylation site of human p27. In experiments based on specific RalA and p27 mutants, complemented with short hairpin RNA-mediated knockdown of Ral downstream signaling components, we show that activation of RalBP1 induces cytoplasmic accumulation of p27 and that this event requires p27 Ser-10 phosphorylation by protein kinase B/Akt. Of note, activation of PLD1 counteracts this effect in a Ser-10-independent manner. The physiological relevance of the modulation of p27 localization by Ral is demonstrated by the ability of Ral-mediated activation of the RalBP1 pathway to abrogate transforming growth factor-β-mediated growth arrest in epithelial cells.

Banales JM, Munoz-Garrido P, Bujanda L
Somatic second-hit mutations leads to polycystic liver diseases.
World J Gastroenterol. 2013; 19(1):141-3 [PubMed] Free Access to Full Article Related Publications
Polycystic liver diseases (PCLDs) are a heterogeneous group of genetic disorders characterized by the development of multiple fluid-filled cysts in the liver, which derive from cholangiocytes, the epithelial cells lining the bile ducts. When these cysts grow, symptoms such as abdominal distension, nausea, and abdominal pain may occur. PCLDs may exist isolated (i.e., autosomal dominant polycystic liver disease, ADPLD) or in combination with renal cystogenesis (i.e., autosomal dominant polycystic kidney disease and autosomal recessive polycystic liver disease). The exact prevalence of PCLDs is unknown, but is estimated to occur in approximately 1:1000 persons. Although the pathogenesis of each form of PCLD appears to be different, increasing evidences indicate that hepatic cystogenesis is a phenomenon that may involve somatic loss of heterozygosity (LOH) in those pathological conditions inherited in a dominant form. A recent report, using highly sophisticated methodology, demonstrated that ADPLD patients with a germline mutation in the protein kinase C substrate 80K-H (PRKCSH) gene mostly develop hepatic cystogenesis through a second somatic mutation. While hepatocystin, the PRKCSH-encoding protein, was absent in the hepatic cysts with LOH, it was still expressed in the heterozygous cysts. On the other hand, no additional trans-heterozygous mutations on the SEC63 homolog (S. cerevisiae/SEC63) gene (also involved in the development of PCLDs) were observed. These data indicate that PCLD is recessive at the cellular level, and point out the important role of hepatocystin loss in cystogenesis. In this commentary, we discuss the knowledge regarding the role of somatic second-hit mutations in the development of PCLDs, and the most relevant findings have been highlighted.

Janssen MJ, Salomon J, Te Morsche RH, Drenth JP
Loss of heterozygosity is present in SEC63 germline carriers with polycystic liver disease.
PLoS One. 2012; 7(11):e50324 [PubMed] Free Access to Full Article Related Publications
Polycystic liver disease (PCLD) is an autosomal dominant disorder characterised by multiple fluid filled cysts in the liver. This rare disease is caused by heterozygous germline mutations in PRKCSH and SEC63. We previously found that, in patients with a PRKCSH mutation, over 76% of the cysts acquired a somatic 'second-hit' mutation in the wild type PRKCSH allele. We hypothesise that somatic second-hit mutations are a general mechanism of cyst formation in PCLD which also plays a role in PCLD patients carrying a SEC63 germline mutation. We collected cyst epithelial cells from 52 liver cysts from three different SEC63 patients using laser microdissection. DNA samples were sequenced to identify loss of heterozygosity (LOH) mutations and other somatic mutations in cyst epithelial DNA. We discovered somatic SEC63 mutations in patient 3 (1/14 cysts), but not in patient 1 and 2 (38 cysts). Upon review we found that the germline mutation of patient 1 and 2 (SEC63 c.1703_1705delAAG) was present in the same frequency in DNA samples from healthy controls, suggesting that this variant is not causative of PCLD. In conclusion, as somatic second-hit mutations also play a role in cyst formation in patients with a SEC63 germline mutation, this appears to be a general mechanism of cyst formation in PCLD.

Kang DW, Hwang WC, Park MH, et al.
Rebamipide abolishes Helicobacter pylori CagA-induced phospholipase D1 expression via inhibition of NFκB and suppresses invasion of gastric cancer cells.
Oncogene. 2013; 32(30):3531-42 [PubMed] Related Publications
Infection with cagA-positive Helicobacter pylori is a risk factor for the development of severe gastritis and gastric cancer (GC). CagA protein is injected into gastric epithelial cells and deregulates a variety of cellular signaling molecules. Phospholipase D (PLD) is elevated in many different types of human cancers and has been implicated as a critical factor in inflammation and carcinogenesis. In this study, we show that infection with cagA-positive H. pylori in GC cells significantly induces PLD1 expression via CagA-dependent activation of nuclear factor κB (NFκB). Interestingly, the level of PLD1 protein and IκBα phosphorylation is aberrantly upregulated in H. pylori-infected human GC tissues. Infection with cagA-positive H. pylori and expression of CagA enhanced the binding of NFκB to the PLD1 promoter, and two functional NFκB-binding sites were identified within the PLD1 promoter. Rebamipide, a mucosal-protective antiulcer agent, abolished H. pylori cagA-induced PLD1 expression via inhibition of binding of NFκB to the PLD1 promoter, and also inhibited PLD activity. Moreover, rebamipide suppressed H. pylori-induced matrix metalloproteinase-9, interleukin-8 and activation-induced cytidine deaminase expression as well as invasion of GC cells through downregulation of PLD1. Our data suggest that H. pylori cagA targets PLD1 for invasion of GC cells, and rebamipide might contribute to the antitumorigenic effect of GC cells via inhibition of the H. pylori cagA-NFκB-PLD1 signaling pathway.

Zingg-Schenk A, Caduff J, Azzarello-Burri S, et al.
Boy with autosomal recessive polycystic kidney and autosomal dominant polycystic liver disease.
Pediatr Nephrol. 2012; 27(7):1197-200 [PubMed] Related Publications
BACKGROUND: Autosomal recessive polycystic kidney disease (ARPKD) shows a great phenotypic variability between patients, ranging from perinatal demise to mildly affected adults. Autosomal dominant polycystic liver disease (PCLD) does not manifest in childhood.
CASE-DIAGNOSIS/TREATMENT: A boy was reported with the co-occurrence of ARPKD and PCLD. He presented at the age of 16 days with pyelonephritis and urosepsis. Subsequent investigations showed enlarged kidneys and hyperechogenic renal medulla and liver parenchyma. Genetic analysis revealed compound heterozygous mutations in the PKHD1 gene (p.Arg496X and p.Ser1862Leu). After his mother was diagnosed with PCLD, the finding of a liver cyst on ultrasound prompted analysis of the PRKCSH gene, revealing a missense mutation (p.Arg139His). At the most recent follow-up at 13 years of age, the patient's course and clinical examination was uneventful with normal renal and liver function without evidence of portal hypertension.
CONCLUSIONS: The patient with ARPKD and PCLD has so far demonstrated a benign clinical outcome, consistent with the great phenotypic variability of ARPKD and, apart from the liver cyst, asymptomatic manifestation of PCLD in childhood. However, close long-term follow-up is mandatory.

Kim HJ, Roh MS, Son CH, et al.
Loss of Med1/TRAP220 promotes the invasion and metastasis of human non-small-cell lung cancer cells by modulating the expression of metastasis-related genes.
Cancer Lett. 2012; 321(2):195-202 [PubMed] Related Publications
Med1/TRAP220 is an essential component of the TRAP/Mediator complex. In this study, we present a novel function of Med1 in human non-small-cell lung cancer (NSCLC) progression. We found that the loss of Med1 expression was strongly associated with increased rates of invasion and metastasis in NSCLC patients. Consistent with lung cancer patient data, the knockdown of Med1 in NSCLC cell lines led to an increase in cell migration and invasion. Med1-depleted cells displayed an increase in metastasis in a xenograft tumor model and in an in vivo metastasis assay. Moreover, a microarray analysis revealed that the mRNA levels of the metastasis-related genes uPAR, ID2, ID4, PTP4A1, PKP3, TGM2, PLD1, TIMP2, RGS2, and HOXA4 were altered upon Med1 knockdown. Collectively, these results suggest that the loss of Med1 increases the invasive potential of human NSCLC cells by modulating the expression of metastasis-related genes.

Cao MD, Döpkens M, Krishnamachary B, et al.
Glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5) expression correlates with malignant choline phospholipid metabolite profiles in human breast cancer.
NMR Biomed. 2012; 25(9):1033-42 [PubMed] Free Access to Full Article Related Publications
Altered choline phospholipid metabolism is a hallmark of cancer, leading to malignant choline metabolite profiles consisting of low glycerophosphocholine (GPC) and high phosphocholine (PC) in human breast cancers. Glycerophosphocholine phosphodiesterase (GPC-PDE) catalyzes the degradation of GPC to free choline and glycerol-3-phosphate. The gene(s) encoding for the GPC-PDE(s) responsible for GPC degradation in breast cancers have not yet been identified. Here, we demonstrate for the first time that the GPC-PDE encoded by glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5) is associated with breast cancer malignancy. Two human breast cancer cell lines (n = 8 and n = 10) and primary human breast tumor samples (n = 19) were studied with combined MRS and quantitative reverse transcription-polymerase chain reaction to investigate several isoforms of GDPD expression with respect to choline phospholipid metabolite levels. Of the five GDPDs tested, GDPD5 was found to be significantly overexpressed in highly malignant estrogen receptor negative (ER(-)) compared with weakly malignant estrogen receptor positive (ER(+)) human breast cancer cells (p = 0.027) and breast tumors from patients (p = 0.015). GDPD5 showed significantly positive correlations with PC (p < 0.001), total choline (tCho) (p = 0.007) and PC/GPC (p < 0.001) levels in human breast tumors. GDPD5 showed a trend towards a negative correlation with GPC levels (p = 0.130). Human breast cancers with malignant choline metabolite profiles consisting of low GPC and high PC levels highly co-expressed GDPD5, choline kinase alpha (CHKA) and phosphatidylcholine-specific phospholipase D1 (PLD1), whereas cancers containing high GPC and relatively low PC levels displayed low co-expression of GDPD5, CHKA and PLD1. GDPD5, CHKA and PLD1 were significantly overexpressed in highly malignant ER(-) tumors in our patient cohort. Our study identified GDPD5 as a GPC-PDE that probably participates in the regulation of choline phospholipid metabolism in breast cancer, which possibly occurs in cooperation with CHKA and PLD1.

Cadenas C, Vosbeck S, Hein EM, et al.
Glycerophospholipid profile in oncogene-induced senescence.
Biochim Biophys Acta. 2012; 1821(9):1256-68 [PubMed] Related Publications
Alterations in lipid metabolism and in the lipid composition of cellular membranes are linked to the pathology of numerous diseases including cancer. However, the influence of oncogene expression on cellular lipid profile is currently unknown. In this work we analyzed changes in lipid profiles that are induced in the course of ERBB2-expression mediated premature senescence. As a model system we used MCF-7 breast cancer cells with doxycycline-inducible expression of NeuT, an oncogenic ERBB2 variant. Affymetrix gene array data showed NeuT-induced alterations in the transcription of many enzymes involved in lipid metabolism, several of which (ACSL3, CHPT1, PLD1, LIPG, MGLL, LDL and NPC1) could be confirmed by quantitative realtime PCR. A study of the glycerophospholipid and lyso-glycerophospholipid profiles, obtained by high performance liquid chromatography coupled to Fourier-transform ion cyclotron resonance-mass spectrometry revealed senescence-associated changes in numerous lipid species, including mitochondrial lipids. The most prominent changes were found in PG(34:1), PG(36:1) (increased) and LPE(18:1), PG(40:7) and PI(36:1) (decreased). Statistical analysis revealed a general trend towards shortened phospholipid acyl chains in senescence and a significant trend to more saturated acyl chains in the class of phosphatidylglycerol. Additionally, the cellular cholesterol content was elevated and accumulated in vacuoles in senescent cells. These changes were accompanied by increased membrane fluidity. In mitochondria, loss of membrane potential along with altered intracellular distribution was observed. In conclusion, we present a comprehensive overview of altered cholesterol and glycerophospholipid patterns in senescence, showing that predominantly mitochondrial lipids are affected and lipid species less susceptible to peroxidation are increased.

Sulzmaier FJ, Valmiki MK, Nelson DA, et al.
PEA-15 potentiates H-Ras-mediated epithelial cell transformation through phospholipase D.
Oncogene. 2012; 31(30):3547-60 [PubMed] Free Access to Full Article Related Publications
The small GTPase H-Ras is a proto-oncogene that activates a variety of different pathways including the extracellular-signal-regulated kinase (ERK)/mitogen-activated protein kinase pathway. H-Ras is mutated in many human malignancies, and these mutations cause the protein to be constitutively active. Phosphoprotein enriched in astrocytes, 15 kDa (PEA-15) blocks ERK-dependent gene transcription and inhibits proliferation by sequestering ERK in the cytoplasm. We therefore investigated whether PEA-15 influences H-Ras-mediated transformation. We found that PEA-15 does not block H-Ras-activated proliferation when H-Ras is constitutively active. We show instead that in H-Ras-transformed mouse kidney epithelial cells, co-expression of PEA-15 resulted in enhanced soft agar colony growth and increased tumor growth in vivo. Overexpression of both H-Ras and PEA-15 resulted in accelerated G1/S cell cycle transition and increased activation of the ERK signaling pathway. PEA-15 mediated these effects through activation of its binding partner phospholipase D1 (PLD1). Inhibition of PLD1 or interference with PEA-15/PLD1 binding blocked PEA-15's ability to increase ERK activation. Our findings reveal a novel mechanism by which PEA-15 positively regulates Ras/ERK signaling and increases the proliferation of H-Ras-transformed epithelial cells through enhanced PLD1 expression and activation. Thus, our work provides a surprising mechanism by which PEA-15 augments H-Ras-driven transformation. These data reveal that PEA-15 not only suppresses ERK signaling and tumorigenesis but also alternatively enhances tumorigenesis in the context of active Ras.

Rani S, O'Driscoll L
Reverse-transcriptase polymerase chain reaction to detect extracellular mRNAs.
Methods Mol Biol. 2011; 784:15-25 [PubMed] Related Publications
The presence of extracellular nucleic acids has been reported in serum/plasma from cancer and diabetes patients that may help in disease diagnosis. Taking insulin-producing cells as examples here, RT-PCR was used to investigate a correlation between the presence and amounts of extracellular mRNA(s) and cell mass and/or function. RT-PCR was performed on a range of mRNAs, including Pdx1, Npy, Egr1, Pld1, Chgb, InsI, InsII, and Actb in biological triplicate analyses.Reproducible amplification of these mRNAs from MIN6, MIN6 B1, and Vero-PPI cells and their CM suggests that beta cells transcribe and release these mRNAs into their environment. mRNAs secreted from insulin-producing cells into their extracellular environment may have potential as extracellular biomarkers for assessing beta cell mass and function.

Janssen MJ, Waanders E, Te Morsche RH, et al.
Secondary, somatic mutations might promote cyst formation in patients with autosomal dominant polycystic liver disease.
Gastroenterology. 2011; 141(6):2056-2063.e2 [PubMed] Related Publications
BACKGROUND & AIMS: Heterozygous germline mutations in PRKCSH cause autosomal dominant polycystic liver disease (PCLD), but it is not clear how they lead to cyst formation. We investigated whether mutations in cyst epithelial cells and corresponding loss of the PRKCSH gene product (hepatocystin) contributed to cyst development.
METHODS: Liver cyst material was collected through laparoscopic cyst fenestration from 8 patients with PCLD who had a heterozygous germline mutation in PRKCSH. Tissue sections from 71 cysts (2-14 per patient) were obtained for hepatocystin staining and mutation analysis. Cyst epithelium was acquired using laser microdissection; DNA was isolated and analyzed for loss of heterozygosity (LOH) and somatic mutations using restriction analysis and sequencing. Common single nucleotide polymorphisms (SNPs) in a 70-kilobase region surrounding the germline mutation were used to determine variations in the genomic region with LOH.
RESULTS: The wild-type allele of PRKCSH was lost (LOH) in 76% of cysts (54/71). Hepatocystin was not detected in cyst epithelia with LOH, whereas heterozygous cysts still expressed hepatocystin. The variation observed in the LOH region analysis indicates that cysts develop independently. We also detected somatic mutations in PRKCSH in 17% (2/12) of the cysts without LOH. Trans-heterozygous mutations in SEC63 were not observed.
CONCLUSIONS: Among patients with PCLD who have a heterozygous germline mutation in PRKCSH, we found secondary, somatic mutations (second hits) in more than 76% of the liver cyst epithelia. PCLD is recessive at the cellular level, and loss of functional PRKCSH is an important step in cystogenesis.

Temmerman F, Missiaen L, Bammens B, et al.
Systematic review: the pathophysiology and management of polycystic liver disease.
Aliment Pharmacol Ther. 2011; 34(7):702-13 [PubMed] Related Publications
BACKGROUND: Polycystic liver diseases (PCLD) represent a group of genetic disorders in which cysts occur solely in the liver, or together with renal cysts. Most of the patients with PCLD are asymptomatic, however, in some patients, expansion of liver cysts causes invalidating abdominal symptoms.
AIM: To provide a systemic review on the pathophysiology and management of PCLD.
METHODS: A PubMed search was undertaken to identify relevant literature using search terms including polycystic liver disease, pathophysiology, surgical and medical management.
RESULTS: The most common complication in patients with PCLD is extensive hepatomegaly, which may lead to malnutrition and can be lethal. Conservative surgical approaches are only partially effective and do not change the natural course of the disease. Liver transplantation has been successfully performed in PCLD, however, in an era of organ shortage, medical management needs to be evaluated. A better understanding of the pathophysiology and the availability of animal models have already identified promising drugs. Abnormalities in cholangiocyte proliferation/apoptosis and enhanced fluid secretion are key factors in the pathophysiology. It has been demonstrated in rodents and in humans that somatostatin analogues diminish liver volume. The role of the inhibitors of the mammalian target of rapamycin (mTOR) in the management of PCLD is still under investigation.
CONCLUSIONS: The exact pathophysiology of polycystic liver disease still remains unclear. In symptomatic patients, none of the currently available surgical options except liver transplantation have been shown to change the natural course of the disease. The use of somatostatin analogues has been shown to diminish liver volume.

Itoh T, Terazawa R, Kojima K, et al.
Cisplatin induces production of reactive oxygen species via NADPH oxidase activation in human prostate cancer cells.
Free Radic Res. 2011; 45(9):1033-9 [PubMed] Related Publications
This study aimed to examine the roles of reactive oxygen species (ROS) in cisplatin treatment of human prostate cancer cells; hormone-sensitive LNCaP and hormone-refractory PC3 and DU145 cells. Intracellular levels of ROS and H(2)O(2) were measured and visualized using specific fluorescent probes. NADPH oxidase (NOX) activity was detected by lucigenin chemiluminescence assay. Expression levels of NOX isoforms were determined by semi-quantitative RT-PCR. Cisplatin treatment increased the intracellular levels of ROS and H(2)O(2) in three prostate cancer cell lines. The increase was transient and robust in hormone-sensitive LNCaP cells compared with hormone-refractory PC3 and DU145 cells. Consistent with these findings, the NOX activity induced by cisplatin was higher in LNCaP cells than in PC3 and DU145 cells. Expression pattern of NOX isoforms varied among three cell lines and the NOX activity was independent of NOX expression. Taken together, we have shown that cisplatin induces production of ROS and H(2)O(2) via NOX activation in human prostate cancer cell lines, which is most prominent in hormone-sensitive LNCaP cells.

Henkels KM, Farkaly T, Mahankali M, et al.
Cell invasion of highly metastatic MTLn3 cancer cells is dependent on phospholipase D2 (PLD2) and Janus kinase 3 (JAK3).
J Mol Biol. 2011; 408(5):850-62 [PubMed] Free Access to Full Article Related Publications
MTLn3 cells are highly invasive breast adenoacarcinoma cells. The relative level of the epidermal-growth-factor-stimulated invasion of this cell line is greater than two other breast cancer cell lines (MDA-MB-231 and MCF-7) and one non-small cell lung cancer cell line (H1299). We have determined that the mechanism of cancer cell invasion involves the presence of an enzymatically active phospholipase D (PLD), with the PLD2 isoform being more relevant than PLD1. PLD2 silencing abrogated invasion, whereas ectopic expression of PLD2 augmented cell invasion in all four cell lines, with an efficacy (MTLn3±MDA-MB-231>H1299±MCF-7) that correlated well with their abilities to invade Matrigel in vitro. We also report that PLD2 is under the control of Janus kinase 3 (JAK3), with the kinase phosphorylating PLD2 at the Y415 residue, thus enabling its activation. Y415 is located downstream of a PH domain and upstream of the catalytic HKD-1 domain of PLD2. JAK3 knockdown abrogated lipase activity and epidermal-growth-factor-stimulated cell invasion directly. For the purposes of activating PLD2 for cell invasion, JAK3 operates via an alternative pathway that is independent of STAT, at least in MTLn3 cells. We also consistently found that JAK3 and PLD2 pathways are utilized at the maximum efficiency (phosphorylation and activity) in highly invasive MTLn3 cells versus a relatively low utilization in the less invasive MCF-7 cell line. In summary, a high level of cell invasiveness of cancer cells can be explained for the first time by combined high JAK3/PLD2 phosphorylation and activity involving PLD2's Y415 residue, which might constitute a novel target to inhibit cancer cell invasion.

Cho JH, Oh DY, Kim HJ, et al.
The TSP motif in AP180 inhibits phospholipase D1 activity resulting in increased efficacy of anticancer drug via its direct binding to carboxyl terminal of phospholipase D1.
Cancer Lett. 2011; 302(2):144-54 [PubMed] Related Publications
Phospholipase D (PLD) has two isoforms, PLD1 and PLD2. Both isoforms are possible candidates for the development of anticancer drugs, since PLDs in several cancer cells act as survival factors. The aim of this study was to elucidate the inhibitory mechanism of PLD1 by AP180 in human cancer cells. Transfection of the human AP180 (hAP180) gene markedly inhibited phobol-12-myristate 13-acetate-induced PLD activity resulting in exacerbation of anticancer drug-induced cell death. Experiments using deletion mutants of hAP180 showed that three amino acids (Thr312-Pro314) are critical for inhibition of PLD1 activity by binding directly to PLD1, and, of these, Ser313 was the most important residue for both binding to and inhibiting PLD1. However, this inhibitory relationship did not exist between hAP180 and PLD2. In addition, the C-terminal region of PLD1 is important for the interaction with hAP180. These results indicated that Thr312-Pro314 (especially Ser313 as a phosphorylation residue) of hAP180 can regulate hPLD1 activity through binding with the C-terminal region of PLD1.

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