SEC63

Gene Summary

Gene:SEC63; SEC63 homolog, protein translocation regulator
Aliases: ERdj2, SEC63L, DNAJC23, PRO2507
Location:6q21
Summary:The Sec61 complex is the central component of the protein translocation apparatus of the endoplasmic reticulum (ER) membrane. The protein encoded by this gene and SEC62 protein are found to be associated with ribosome-free SEC61 complex. It is speculated that Sec61-Sec62-Sec63 may perform post-translational protein translocation into the ER. The Sec61-Sec62-Sec63 complex might also perform the backward transport of ER proteins that are subject to the ubiquitin-proteasome-dependent degradation pathway. The encoded protein is an integral membrane protein located in the rough ER. [provided by RefSeq, Jul 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:translocation protein SEC63 homolog
HPRD
Source:NCBIAccessed: 11 August, 2015

Ontology:

What does this gene/protein do?
Show (8)

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 11 August 2015 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.

  • DNA-Binding Proteins
  • Signal Transduction
  • Base Sequence
  • Polymorphism
  • alpha-Glucosidases
  • Microsatellite Repeats
  • TRPP Cation Channels
  • Single Nucleotide Polymorphism
  • Cysts
  • Frameshift Mutation
  • Microsatellite Instability
  • Endoplasmic Reticulum
  • Liver Diseases
  • Genotype
  • Germ-Line Mutation
  • Disease Models, Animal
  • Membrane Proteins
  • Polycystic Kidney Diseases
  • Immunohistochemistry
  • Nuclear Proteins
  • Loss of Heterozygosity
  • Exome
  • Genetic Markers
  • Glucosidases
  • Phenotype
  • Mutation
  • Protein Transport
  • Chromosome 6
  • Pedigree
  • Polymerase Chain Reaction
  • Cancer Gene Expression Regulation
  • bcl-2-Associated X Protein
  • X-Ray Computed Tomography
  • Colorectal Cancer
  • Phosphoproteins
  • Hereditary Nonpolyposis Colorectal Cancer (HNPCC)
  • Intracellular Signaling Peptides and Proteins
  • Genetic Predisposition
  • Young Adult
  • DNA Mutational Analysis
Tag cloud generated 11 August, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (2)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: SEC63 (cancer-related)

Gruel N, Benhamo V, Bhalshankar J, et al.
Polarity gene alterations in pure invasive micropapillary carcinomas of the breast.
Breast Cancer Res. 2014; 16(3):R46 [PubMed] Free Access to Full Article Related Publications
INTRODUCTION: Pure invasive micropapillary carcinoma (IMPC) is a special type of breast carcinoma characterised by clusters of cells presenting polarity abnormalities. The biological alterations underlying this pattern remain unknown.
METHODS: Pangenomic analysis (n=39), TP53 (n=43) and PIK3CA (n=41) sequencing in a series of IMPCs were performed. A subset of cases was also analysed with whole-exome sequencing (n=4) and RNA sequencing (n=6). Copy number variation profiles were compared with those of oestrogen receptors and grade-matched invasive ductal carcinomas (IDCs) of no special type.
RESULTS: Unsupervised analysis of genomic data distinguished two IMPC subsets: one (Sawtooth/8/16) exhibited a significant increase in 16p gains (71%), and the other (Firestorm/Amplifier) was characterised by a high frequency of 8q (35%), 17q (20% to 46%) and 20q (23% to 30%) amplifications and 17p loss (74%). TP53 mutations (10%) were more frequently identified in the amplifier subset, and PIK3CA mutations (4%) were detected in both subsets. Compared to IDC, IMPC exhibited specific loss of the 6q16-q22 region (45%), which is associated with downregulation of FOXO3 and SEC63 gene expression. SEC63 and FOXO3 missense mutations were identified in one case each (2%). Whole-exome sequencing combined with RNA sequencing of IMPC allowed us to identify somatic mutations in genes involved in polarity, DNAH9 and FMN2 (8% and 2%, respectively) or ciliogenesis, BBS12 and BBS9 (2% each) or genes coding for endoplasmic reticulum protein, HSP90B1 and SPTLC3 (2% each) and cytoskeleton, UBR4 and PTPN21 (2% each), regardless of the genomic subset. The intracellular biological function of the mutated genes identified by gene ontology analysis suggests a driving role in the clinicopathological characteristics of IMPC.
CONCLUSION: In our comprehensive molecular analysis of IMPC, we identified numerous genomic alterations without any recurrent fusion genes. Recurrent somatic mutations of genes participating in cellular polarity and shape suggest that they, together with other biological alterations (such as epigenetic modifications and stromal alterations), could contribute to the morphological pattern of IMPC. Though none of the individual abnormalities demonstrated specificity for IMPC, whether their combination in IMPC may have a cumulative effect that drives the abnormal polarity of IMPC needs to be examined further with in vitro experiments.

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.

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.

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.

Casper M, Weber SN, Kloor M, et al.
Hepatocellular carcinoma as extracolonic manifestation of Lynch syndrome indicates SEC63 as potential target gene in hepatocarcinogenesis.
Scand J Gastroenterol. 2013; 48(3):344-51 [PubMed] Related Publications
OBJECTIVE: Lynch syndrome is a cancer predisposition syndrome caused by germline mutations in DNA mismatch repair (MMR) genes with microsatellite instability (MSI) as its molecular hallmark. Hepatocellular carcinoma (HCC) has not been considered part of the tumor spectrum. The aim was to provide a detailed molecular characterization of an HCC associated with Lynch Syndrome (Muir-Torre variant).
MATERIALS AND METHODS: HCC samples were analyzed for MSI, MMR protein expression and coding microsatellite instability (cMSI). Since cMSI also affected SEC63 coding for an endoplasmic reticulum membrane protein with implications for intracellular protein translocation, its impact on hepatocyte growth control was assessed in an established short-term model. Recombinant inbred mouse lines (BXD) showing different basal SEC63 expression levels were treated with the chemocarcinogen diethylnitrosamine (DEN) intraperitoneally. Proliferation and apoptosis of hepatocytes were determined after 48 h using Ki67 and TUNEL assays.
RESULTS: The HCC was high-grade microsatellite unstable with loss of MSH2 expression. cMSI was detected in four genes (ASTE1, SEC63, TAF1B, TGFBR2). However, only TGFBR2 is known to be involved in hepatocarcinogenesis. When investigating the impact of SEC63 expression on hepatocyte growth control in the murine model, low hepatic expression correlated significantly (p < 0.05) with a decrease in apoptosis and increased proliferative activity.
CONCLUSIONS: For the first time, an HCC with characteristic molecular features of association with Lynch syndrome is described. The pro-carcinogenic growth behavior of hepatocytes with low SEC63 expression in the murine model indicates a potential role for SEC63 in hepatocarcinogenesis in general, but this needs further functional validation.

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.

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.

Müller L, Funato Y, Miki H, Zimmermann R
An interaction between human Sec63 and nucleoredoxin may provide the missing link between the SEC63 gene and polycystic liver disease.
FEBS Lett. 2011; 585(4):596-600 [PubMed] Related Publications
The formation of multiple cysts in one or several organs is a characteristic of several human inherited diseases. Recent research suggests that problems in planar cell polarity may be the common denominator in polycystic diseases. Mutations in at least two genes are linked to autosomal dominant polycystic liver disease (PCLD), PRKCSH and SEC63. A recent study linked PRKCSH to the signaling- and cytoskeletal adaptor-component β-catenin. In a yeast two hybrid screen we identified the cytosolic protein nucleoredoxin (NRX) as an interaction partner of human Sec63. Since NRX is involved in the Wnt signaling pathways, we characterized this interaction. Thus, Sec63 is linked to the Wnt signaling pathways and this interaction may be the reason why mutations in SEC63 can lead to PCLD.

Van Keimpema L, De Koning DB, Van Hoek B, et al.
Patients with isolated polycystic liver disease referred to liver centres: clinical characterization of 137 cases.
Liver Int. 2011; 31(1):92-8 [PubMed] Related Publications
BACKGROUND AND AIM: Isolated polycystic liver disease (PCLD) is characterized by the presence of multiple cysts in the liver in the absence of polycystic kidneys. The clinical profile of PCLD is poorly defined and we set up a study for the clinical characteristics of PCLD.
METHODS: We collected clinical data on 188 PCLD patients (defined as >10 liver cysts) from five tertiary referral centres, and 137 patients were selected for the purpose of this study. We performed molecular analysis of the PCLD associated genes PRKCSH and SEC63 in 91 patients.
RESULTS: A total of 118 (86%) patients were female. The majority of patients (88%) had >20 cysts. The median age at diagnosis was 47 years (range 23-84). 37 (41%) patients carried a mutation. Clinical symptoms at presentation were present in 111 (84%) patients. γ-glutamyl transferase was elevated to 1.4 times upper limit of normal (interquartile range 1.0-2.7). The presence of a mutation and female gender predicted a more severe course: female patients were 9 years younger at the time of diagnosis (47 years; range 23-84) and 91% had symptoms (P<0.01); likewise, mutation carriers were younger at presentation (39 years; range 35-48) and 95% of this cohort had symptoms (P<0.01). During follow-up [median 8.2 years (range 0-35)], 10% of untreated and 51% of treated patients developed complications. Mortality in this cohort was 8%, but only 2% died of PCLD-related causes. 58% of patients were treated a median of 2 years (range 0-25) after diagnosis.
CONCLUSION: Symptomatic PCLD patients are mainly females. Females and mutation carriers were younger at diagnosis and had a more severe course of disease.

Janssen MJ, Waanders E, Woudenberg J, et al.
Congenital disorders of glycosylation in hepatology: the example of polycystic liver disease.
J Hepatol. 2010; 52(3):432-40 [PubMed] Related Publications
Autosomal dominant polycystic liver disease (PCLD) is a rare progressive disorder characterized by an increased liver volume due to many (>20) fluid-filled cysts of biliary origin. Disease causing mutations in PRKCSH or SEC63 are found in approximately 25% of the PCLD patients. Both gene products function in the endoplasmic reticulum, however, the molecular mechanism behind cyst formation remains to be elucidated. As part of the translocon complex, SEC63 plays a role in protein import into the ER and is implicated in the export of unfolded proteins to the cytoplasm during ER-associated degradation (ERAD). PRKCSH codes for the beta-subunit of glucosidase II (hepatocystin), which cleaves two glucose residues of Glc(3)Man(9)GlcNAc(2) N-glycans on proteins. Hepatocystin is thereby directly involved in the protein folding process by regulating protein binding to calnexin/calreticulin in the ER. A separate group of genetic diseases affecting protein N-glycosylation in the ER is formed by the congenital disorders of glycosylation (CDG). In distinct subtypes of this autosomal recessive multisystem disease specific liver symptoms have been reported that overlap with PCLD. Recent research revealed novel insights in PCLD disease pathology such as the absence of hepatocystin from cyst epithelia indicating a two-hit model for PCLD cystogenesis. This opens the way to speculate about a recessive mechanism for PCLD pathophysiology and shared molecular pathways between CDG and PCLD. In this review we will discuss the clinical-genetic features of PCLD and CDG as well as their biochemical pathways with the aim to identify novel directions of research into cystogenesis.

Deschoolmeester V, Baay M, Wuyts W, et al.
Detection of microsatellite instability in colorectal cancer using an alternative multiplex assay of quasi-monomorphic mononucleotide markers.
J Mol Diagn. 2008; 10(2):154-9 [PubMed] Free Access to Full Article Related Publications
Colorectal malignancies demonstrating microsatellite instability (MSI) have a very heterogeneous histological appearance, better prognosis, and altered response to therapy. Consequently, identification of the MSI phenotype is both relevant and interesting as a screening and prognostic tool and as a potential predictive factor of chemotherapeutic response. Several groups have argued for the exclusive use of mononucleotide markers for MSI analysis. In this study, an alternative MSI typing multiplex system of mononucleotide microsatellite repeats was developed. This system obviates the need to compare allelic profiles between tumor and matching normal DNA, rendering MSI analysis amenable to high throughput. The quasi-monomorphic allelic distribution of five alternative mononucleotide markers was evaluated in genomic DNA. Only SEC63 and CAT25 were found to be quasi-monomorphic and were thus combined with BAT25 and BAT26 from the Bethesda panel. Consequently, 177 colorectal cancer samples previously analyzed by the Bethesda panel were tested for MSI using this alternative mononucleotide panel. In an attempt to resolve discordant cases, immunohistochemistry of MLH1, MSH2, and MSH6 was performed. The concordance between both panels reached 99.4% when microsatellite stability and MSI-L were grouped together. These new markers were subsequently multiplexed in a single polymerase chain reaction assay. The resulting mononucleotide fluorescent multiplex MSI assay has high accuracy, reliability, and throughput, thus reducing the time and cost involved in MSI testing.

Hirata T, Yamamoto H, Taniguchi H, et al.
Characterization of the immune escape phenotype of human gastric cancers with and without high-frequency microsatellite instability.
J Pathol. 2007; 211(5):516-23 [PubMed] Related Publications
Gastric cancers with and without high-frequency microsatellite instability (MSI-H) represent distinctive pathways of carcinogenesis. The aim of this study was to clarify if human leukocyte antigen (HLA) class I antigen subunits and antigen processing machinery (APM) components are differentially downregulated in these two groups of tumours. Using reverse transcription PCR (RT-PCR), loss of heterozygosity (LOH) analysis, methylation-specific PCR (MSP), DNA sequencing, immunohistochemistry, and flow cytometry, we analysed expression and/or alteration of HLA class I antigen subunits and APM components, including low molecular weight polypeptide proteasome subunit (LMP)2, LMP7, LMP10, transporter associated with antigen processing (TAP)1, TAP2, tapasin, proteasome activator (PA) 28alpha, and PA28beta in two stage-matched panels of 30 MSI-H and 30 microsatellite stable (MSS) gastric cancers. Mutations at coding microsatellites (cMS) located within beta2-microglobulin (beta2m) and genes encoding APM components, including endoplasmic reticulum (ER) chaperone protein genes, such as calnexin, SEC63, SEC31, and P4HB (p55), were also analysed. HLA class Ia transcripts were totally downregulated in 18.3% of cancer cases. Locus-specific downexpression of HLA-A, -B, and -C was detected in 41.7%, 45.0%, and 31.7% of cases. Loss of HLA-A was significantly more frequent in MSI-H cancers. The LOH ratios of the HLA-A, -B, and -C loci microsatellite markers were relatively low: 5/32 (15.6%) for D6S306, 4/32 (12.5%) for D6S258, 4/33 (12.1%) for D6S273, and 4/30 (13.3%) for D6S1666. Methylation of HLA-A, -B, and -C was detected in 38.3%, 40.0%, and 28.3% of cases. A significant association between methylation and reduction in expression was observed in gastric cancer tissues. Mutations at cMS of beta2m and APM components were detected in 3.3-46.7% of MSI-H cancers but in none of MSS cancers. These data show that gastric cancers have various defects in HLA class I antigen subunits and APM components and that the MSI phenotype is associated with frequent HLA-A inactivation and frameshift mutations of the beta2m and APM genes.

Zimmermann R, Müller L, Wullich B
Protein transport into the endoplasmic reticulum: mechanisms and pathologies.
Trends Mol Med. 2006; 12(12):567-73 [PubMed] Related Publications
Transport into the endoplasmic reticulum (ER) is the crucial step in the biosynthesis of most secretory proteins and many membrane proteins. The products of the SIL1, SEC62 and SEC63 genes act in concert with the SEC61 complex and the molecular chaperones BiP and GRP170 to transport proteins into the ER. Interestingly, recent genetic work has linked mutations in the human and murine SIL1 genes to neurodegeneration, and mutations in the human SEC63 gene to autosomal dominant polycystic liver disease. Furthermore, mutations in the SEC63 gene and overexpression of the SEC62 gene are associated with various human cancers. Therefore, we suggest that these diseases should be considered to be pathologies of protein transport into the ER rather than protein-folding diseases.

Waanders E, te Morsche RH, de Man RA, et al.
Extensive mutational analysis of PRKCSH and SEC63 broadens the spectrum of polycystic liver disease.
Hum Mutat. 2006; 27(8):830 [PubMed] Related Publications
Autosomal dominant polycystic liver disease (PCLD) is characterized by progressive development of multiple (> 20) liver cysts. Two separate genes, PRKCSH and SEC63, have been identified to cause familial PCLD. We designed this study with two goals: to assess the relative contribution of PRKCSH and SEC63 mutations in a cohort of unrelated patients with a variable number of liver cysts, and to assess the effect of these mutations on the severity of the PCLD phenotype. We selected patients with two or more liver cysts on radiological studies and excluded those with renal cysts. A total of 51 patients entered the study and three groups were distinguished: A, 2-10 cysts (18 patients); B, 11-20 cysts (nine patients); and C, more than 20 cysts (24 patients). In total we found that eight patients with multiple liver cysts (16%) had PRKCSH (5) or SEC63 (3) mutations. Two patients (11%) from group A had missense mutations (1 PRKCSH and 1 SEC63). Six patients (25%) with more than 20 liver cysts had mutations (4 PRKCSH and 2 SEC63), of which five mutations were chain-terminating. In conclusion, both PRKCSH and SEC63 mutations are associated with polycystic liver disease. Frequency and severity of mutations is higher among patients with more than 20 liver cysts, but also patients with as few as eight liver cysts can be mutation carriers.

Tahvanainen E, Tahvanainen P, Kääriäinen H, Höckerstedt K
Polycystic liver and kidney diseases.
Ann Med. 2005; 37(8):546-55 [PubMed] Related Publications
There have been remarkable advances in research on polycystic liver and kidney diseases recently, covering cloning of new genes, refining disease classifications, and advances in understanding more about the molecular pathology of these diseases. Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary disease affecting kidneys. It affects 1/400 to 1/1000 live births and accounts for 5% of the end stage renal disease in the United States and Europe, and is caused by gene defects in the PKD1 or PKD2 genes. Compared to ADPKD, polycystic liver disease (PCLD) is a milder disease and does not lower life expectancy. Both diseases are usually adult-onset diseases. Defects in genes, which code the hepatocystin and SEC63 proteins, have just recently been found to cause PCLD. It now seems that ADPKD is caused by malfunction of the primary cilia, a cell organ sensing fluid movement, and that PCLD is a sequel from defects in protein processing. Autosomal recessive polycystic kidney disease (ARPKD) belongs to a group of congenital hepatorenal fibrocystic syndromes. All ARPKD patients have a gene defect in a gene called PKHD1, the protein product of which localizes to primary cilia. We summarize the present clinical and molecular knowledge of these diseases in this review.

Drenth JP, Martina JA, van de Kerkhof R, et al.
Polycystic liver disease is a disorder of cotranslational protein processing.
Trends Mol Med. 2005; 11(1):37-42 [PubMed] Related Publications
Autosomal-dominant polycystic liver disease (PCLD) is a rare disorder that is characterized by the progressive development of fluid-filled biliary epithelial cysts in the liver. Positional cloning has identified two genes that are mutated in patients with polycystic liver disease, PRKCSH and SEC63, which encode the beta-subunit of glucosidase II and Sec63, respectively. Both proteins are components of the molecular machinery involved in the translocation, folding and quality control of newly synthesized glycoproteins in the endoplasmic reticulum. Most mutations are truncating and probably lead to a complete loss of the corresponding proteins and the defective processing of a key regulator of biliary cell growth. The finding that PCLD is caused by proteins involved in oligosaccharide processing was unexpected and implicates a new avenue for research into neocystogenesis, and might ultimately result in the identification of novel therapeutic drugs.

Mori Y, Sato F, Selaru FM, et al.
Instabilotyping reveals unique mutational spectra in microsatellite-unstable gastric cancers.
Cancer Res. 2002; 62(13):3641-5 [PubMed] Related Publications
Microsatellite instability (MSI) within coding regions causes frameshift mutations (FSMs). This type of mutation may inactivate tumor suppressor genes in cancers with frequent MSI (MSI-H cancers). To identify novel FSMs in gastric carcinogenesis in an unbiased and comprehensive manner, we screened for this type of mutation at 154 coding region repeat loci in 18 MSI-H gastric cancers. We also compared FSM rates and spectra in MSI-H gastric versus colorectal cancers. Thirteen novel loci showed FSMs in >20% of gastric tumors. Novel loci with the highest mutation frequencies included the activin type 2 receptor gene (44.4%), DKFZp564K112 (a homologue of the Drosophila tumor suppressor gene multi-sex-combs; 41.2%), and an endoplasmic reticulum chaperone protein gene SEC63 (37.5%). The mutational spectra for genes with high mutation frequencies were also significantly different between MSI-H gastric and colorectal cancers.

Mori Y, Yin J, Rashid A, et al.
Instabilotyping: comprehensive identification of frameshift mutations caused by coding region microsatellite instability.
Cancer Res. 2001; 61(16):6046-9 [PubMed] Related Publications
Coding region frameshift mutation caused by microsatellite instability (MSI) is one mechanism contributing to tumorigenesis in cancers with MSI in high frequency. Mutation of TGFBR2 is one example of this process. To identify additional examples, a large-scale genomic screen of coding region microsatellites was conducted. 1115 coding homopolymeric loci with six or more nucleotides were identified in an online genetic database. Mutational screening was performed at 152 of these loci in 46 colorectal tumors with MSI in high frequency. Nine loci were mutated in > or =20% of tumors, 10 loci in 10-20%, 24 loci in 5-10%, 43 loci in <5%, and 66 loci were not mutated in any tumors. The most frequently mutated novel loci were the activin type II receptor gene (58.1%), SEC63 (48.8%), AIM 2 (47.6%), a gene encoding a subunit of the NADH-ubiquinone oxidoreductase complex (27.9%), a homologue of mouse cordon-bleu (23.8%), and EBP1/PA2G4 (20.9%). This genome-wide approach identifies coding region MSI in genes or pathways not implicated previously in colorectal tumorigenesis, which may merit functional study or other additional analysis.

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Cite this page: Cotterill SJ. SEC63, Cancer Genetics Web: http://www.cancer-genetics.org/SEC63.htm Accessed:

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