Expression of pre-selected TMEMs with predicted ER localization as potential classifiers of ccRCC tumors

Analysis of the genomic architecture of a complex trait locus in hypertensive rat models links Tmem63c to kidney damage

Unraveling the genetic susceptibility of complex diseases such as chronic kidney disease remains challenging. Here, we used inbred rat models of kidney damage associated with elevated blood pressure for the comprehensive analysis of a major albuminuria susceptibility locus detected in these models. We characterized its genomic architecture by congenic substitution mapping, targeted next-generation sequencing, and compartment-specific RNA sequencing analysis in isolated glomeruli. This led to prioritization of transmembrane protein Tmem63c as a novel potential target. Tmem63c is differentially expressed in glomeruli of allele-specific rat models during onset of albuminuria. Patients with focal segmental glomerulosclerosis exhibited specific TMEM63C loss in podocytes. Functional analysis in zebrafish revealed a role for tmem63c in mediating the glomerular filtration barrier function. Our data demonstrate that integrative analysis of the genomic architecture of a complex trait locus is a powerful tool for identification of new targets such as Tmem63c for further translational investigation.

The human kidneys filter the entire volume of the blood about 300 times each day. This ability depends on specialized cells, known as podocytes, which wrap around some of the blood vessels in the kidney. These cells control which molecules leave the blood based on their size. Normally large molecules like proteins are blocked, while smaller molecules including waste products, toxins, excess water and salts pass through into the urine.

If this filtration system is damaged, by high blood pressure, for example, it can lead to chronic kidney disease. A hallmark of this disease, often called CKD for short, is high levels of the protein albumin in the urine. Previous studies involving rats with high blood pressure have found several regions of the genome that contribute to high levels of albumin in the urine, including one on chromosome 6. However, this region contains several genes and it was unclear which genes affected the condition.

Schulz et al. set out to narrow down the list and find specific genes that might contribute to elevated albumin in the urine of rats with high blood pressure. This search identified the gene for a protein called TMEM63c as a likely candidate. This protein spans the outer membrane of podocyte cells. Analysis of kidney biopsies showed that patients with chronic kidney disease also had low levels of this protein in their podocytes. Further experiments, this time in zebrafish, showed that reducing the activity of the gene for tmem63c led to damaged podocytes and a leakier filter in the kidneys.

The results suggest that this gene plays an important role in the integrity of the kidneys filtration barrier. It is possible that faulty versions of this gene are behind some cases of chronic kidney disease. If this proves to be the case, a better understanding of the role of this gene may lead to new treatments for the condition.

TNF-α-induced miR-450a mediates TMEM182 expression to promote oral squamous cell carcinoma motility

Distant metastasis leads oral cancer patients into a poor survival rate and a high recurrence stage. During tumor progression, dysregulated microRNAs (miRNAs) have been reported to involve tumor initiation and modulate oral cancer malignancy. MiR-450a was significantly upregulated in oral squamous cell carcinoma (OSCC) patients without functional reports. This study was attempted to uncover the molecular mechanism of novel miR-450a in OSCC. Mir-450a expression was examined by quantitative RT-PCR, both in OSCC cell lines and patients. Specific target of miR-450a was determined by software prediction, luciferase reporter assay, and correlation with target protein expression. The functions of miR-450a and TMEM182 were accessed by adhesion and transwell invasion analyses. Determination of the expression and cellular localization of TMEM182 was examined by RT-PCR and by immunofluorescence staining. The signaling pathways involved in regulation of miR-450a were investigated using the kinase inhibitors. Overexpression of miR-450a in OSCC cells impaired cell adhesion ability and induced invasiveness, which demonstrated the functional role of miR-450a as an onco-miRNA. Interestingly, tumor necrosis factor alpha (TNF-α)-mediated expression of TMEM182 was regulated by miR-450a induction. MiR-450a-reduced cellular adhesion was abolished by TMEM182 restoration. Furthermore, the oncogenic activity of TNF-α/miR-450a/TMEM182 axis was primarily through activating extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. ERK1/2 inhibitor prevented the TNF-α-induced miR-450a expression and enhanced adhesion ability. Our data suggested that TNF-α-induced ERK1/2-dependent miR-450a against TMEM182 expression exerted a great influence on increasing OSCC motility. Overall, our results provide novel molecular insights into how TNF-α contributes to oral carcinogenesis through miR-450a that targets TMEM182.

PLAIDOH: a novel method for functional prediction of long non-coding RNAs identifies cancer-specific LncRNA activities

BACKGROUND

Long non-coding RNAs (lncRNAs) exhibit remarkable cell-type specificity and disease association. LncRNA's functional versatility includes epigenetic modification, nuclear domain organization, transcriptional control, regulation of RNA splicing and translation, and modulation of protein activity. However, most lncRNAs remain uncharacterized due to a shortage of predictive tools available to guide functional experiments.

RESULTS

To address this gap for lymphoma-associated lncRNAs identified in our studies, we developed a new computational method, Predicting LncRNA Activity through Integrative Data-driven 'Omics and Heuristics (PLAIDOH), which has several unique features not found in other methods. PLAIDOH integrates transcriptome, subcellular localization, enhancer landscape, genome architecture, chromatin interaction, and RNA-binding (eCLIP) data and generates statistically defined output scores. PLAIDOH's approach identifies and ranks functional connections between individual lncRNA, coding gene, and protein pairs using enhancer, transcript cis-regulatory, and RNA-binding protein interactome scores that predict the relative likelihood of these different lncRNA functions. When applied to 'omics datasets that we collected from lymphoma patients, or to publicly available cancer (TCGA) or ENCODE datasets, PLAIDOH identified and prioritized well-known lncRNA-target gene regulatory pairs (e.g., HOTAIR and HOX genes, PVT1 and MYC), validated hits in multiple lncRNA-targeted CRISPR screens, and lncRNA-protein binding partners (e.g., NEAT1 and NONO). Importantly, PLAIDOH also identified novel putative functional interactions, including one lymphoma-associated lncRNA based on analysis of data from our human lymphoma study. We validated PLAIDOH's predictions for this lncRNA using knock-down and knock-out experiments in lymphoma cell models.

CONCLUSIONS

Our study demonstrates that we have developed a new method for the prediction and ranking of functional connections between individual lncRNA, coding gene, and protein pairs, which were validated by genetic experiments and comparison to published CRISPR screens. PLAIDOH expedites validation and follow-on mechanistic studies of lncRNAs in any biological system. It is available at https://github.com/sarahpyfrom/PLAIDOH .

Transmembrane protein 2 inhibits Zika virus replication through activation of the Janus kinase/signal transducers and activators of transcription signaling pathway

Aim: TMEM2 has been demonstrated to suppress HBV infection by activating the Jak/STAT pathway. In this study, we sought to explore the mechanism by which TMEM2 effects on Zika virus (ZIKV) replication. Materials & methods: TMEM2 was overexpressed. Selected gene mRNA, p-STAT1 levels and interferon stimulated response element activity were examined by qRT-PCR, Western blot and luciferase assay respectively. Results: Overexpression of TMEM2 significantly inhibited ZIKV replication, upregulated MDA5 and RIG-I expression, increased IFN-β promoter activity and IFN-β expression. Overexpression of TMEM2 enhanced the Jak/STAT signaling including increased p-STAT1 level, ISRE activity as well as the expression of several antiviral interferon-stimulated genes. Conclusion: TMEM2 inhibited ZIKV replication through increased IFN-β production and enhanced activation of the Jak/STAT signaling pathway.

TMEM Proteins in Cancer: A Review

A transmembrane protein (TMEM) is a type of protein that spans biological membranes. Many of them extend through the lipid bilayer of the plasma membrane but others are located to the membrane of organelles. The TMEM family gathers proteins of mostly unknown functions. Many studies showed that TMEM expression can be down- or up-regulated in tumor tissues compared to adjacent healthy tissues. Indeed, some TMEMs such as TMEM48 or TMEM97 are defined as potential prognostic biomarkers for lung cancer. Furthermore, experimental evidence suggests that TMEM proteins can be described as tumor suppressors or oncogenes. TMEMs, such as TMEM45A and TMEM205, have also been implicated in tumor progression and invasion but also in chemoresistance. Thus, a better characterization of these proteins could help to better understand their implication in cancer and to allow the development of improved therapy strategies in the future. This review gives an overview of the implication of TMEM proteins in cancer.

The role and regulation of TMEM2 (transmembrane protein 2) in HYBID (hyaluronan (HA)-binding protein involved in HA depolymerization/ KIAA1199/CEMIP)-mediated HA depolymerization in human skin fibroblasts

We have previously reported that HYBID (hyaluronan (HA)-binding protein involved in HA depolymerization/KIAA1199/CEMIP) is a specific HA-binding protein that is essential for HA depolymerization in skin and synovial fibroblasts. HA is incorporated into cells in the presence of HYBID and clathrin, degraded in endosomes, and excreted into the extracellular space. However, it is not yet clear whether HYBID itself catalytically cleaves HA. A recent report on transmembrane protein 2 (TMEM2)-a novel cell surface hyaluronidase-prompted us to investigate whether TMEM2 is essential for HYBID-mediated HA depolymerization. In the present study, we found that transforming growth factor beta 1 (TGF-β1), which suppressed HA depolymerization with a concomitant decrease in HYBID expression, upregulated TMEM2 expression conversely in human skin fibroblasts. TMEM2 expression was not affected by histamine, which significantly increased HA depolymerization accompanied by an increase in HYBID expression. We confirmed a similar response in two other cell lines: KEL FIB keloid fibroblasts and HT1080 fibrosarcoma cells. TGF-β1 was the only inducer of TMEM2 expression among growth factors including epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), and platelet-derived growth factor-BB (PDGF-BB), which suppressed HYBID expression. Moreover, HYBID knockdown completely suppressed HA depolymerization, whereas TMEM2 knockdown unexpectedly enhanced it. These findings clearly indicate that HYBID is indispensable, but TMEM2 is not involved in the HYBID-mediated HA depolymerization system as a catalytic hyaluronidase in human skin fibroblasts.

Cancerous Protein Network That Inhibits the Tumor Suppressor Function of WW Domain-Containing Oxidoreductase (WWOX) by Aberrantly Expressed Molecules

Recent findings indicate that the WW domain-containing oxidoreductase (WWOX) is a tumor suppressor protein that contains two N-terminal WW domains and a central short-chain dehydrogenase/reductase domain. WWOX protein mediates multiple signaling networks that suppress carcinogenesis through binding of its first WW domain to various cancer-associated proteins, i.e., p73, AP-2γ, and others. Although the tumor suppressor property of WWOX is inarguable, WWOX is not inactivated in the manner characteristic of the canonical Knudson hypothesis. Impairment of both alleles of WWOX is thought to be a rare event, only occurring in a few cancer cell lines. How is the tumor suppressor function of WWOX impaired in cancer cells? Recent advances highlight that a small transmembrane protein possessing a PPxY motif, called TMEM207, and its relatives are aberrantly expressed in various cancer cells and hinder the tumor suppressor function of WWOX through inhibiting its WW domain. Here, we review the recent findings related to the pathobiological properties of TMEM207 and its relatives based on clinicopathological and experimental pathological studies.

TMEM17 promotes malignant progression of breast cancer via AKT/GSK3β signaling

Purpose

Current knowledge of TMEM17, a recently identified protein of the transmembrane (TMEM) family, is limited, especially with respect to its expression and biological functions in malignant tumors. This study analyzed TMEM17 expression in invasive breast cancer tissue and breast cell lines and its relevance to clinicopathological factors, and investigated the mechanisms underlying the biological effects of TMEM17 on breast cancer cells.

Patients and methods

TMEM17 protein expression was determined in 20 freshly harvested specimens (tumor and paired normal tissues) by Western blotting. Immunohistochemical analysis was performed to determine the expression and subcellular localization of TMEM17 in samples from 167 patients (mean age, 49 years) diagnosed with invasive ductal carcinoma (38 with triple-negative breast cancer; 129 with non-triple-negative breast cancer) who underwent complete resection in the First Affiliated Hospital of China Medical University between 2011 and 2013. Furthermore, TMEM17 was knocked down by small interfering RNAs in breast cancer cell lines.

Results

TMEM17 was found to be significantly upregulated in breast cancer tissues compared to the corresponding normal breast tissues by Western blotting (p=0.015). Immunohistochemical analysis revealed that TMEM was significantly upregulated in invasive breast cancer cells compared to adjacent normal breast duct glandular epithelial cells (10.78% vs 76.05%, p<0.001), and its expression was closely related to the patient’s T-stage (p=0.022), advanced TNM stages (p=0.007), and lymph node metastasis (p=0.012). After TMEM17 knockdown or overexpression in breast cancer cell lines, TMEM17 upregulated p-AKT, p-GSK3β, active β-catenin, and Snail, and downstream target proteins c-myc and cyclin D1, and downregulated E-cadherin, resulting in increased cancer cell proliferation, invasion, and migration. These effects were reversed by the AKT inhibitor LY294002.

Conclusion

Our results indicate that TMEM17 is upregulated in breast cancer tissues and can promote malignant progression of breast cancer cells by activating the AKT/GSK3β signaling pathway.

TMEM119 silencing inhibits cell viability and causes the apoptosis of gastric cancer SGC-7901 cells

Gastric cancer is the second major cause of death associated with cancer and ranks among the top four cancers diagnosed worldwide. Previous findings identified the association of transmembrane proteins (TMEMs) with tumorigenesis of various types of cancer, including breast, liver and kidney cancer. However, the expression and the biological function of TMEMs, especially TMEM119, and its possible molecular mechanism in gastric cancer remain less understood. CCK-8 and flow cytometric analysis was employed to examine the viability and apoptosis of gastric adenocarcinoma SGC-7901 and AGS cells, gastric carcinoma MKN45 cells, as well as gastric epithelial cell lines GES-1 after transfection with TMEM119-siRNA (siTMEM119), respectively. Quantitative PCR, western blot analysis and immunohistochemistry was performed to detect the expression levels of TMEM119, Bax, Bcl-2 and caspase-3. The results showed that, TMEM119 was elevated with the highest expression detected in SGC-7901 cells compared to AGS cells, MKN45 cells, as well as GES-1. TMEM119 silencing in the gastric cancer cell line, SGC-7901, significantly inhibited cell viability and induced apoptosis. The downregulation of TMEM119 exhibited reduced levels of Bcl-2 and higher levels of Bax and caspase-3 in SGC-7901 cells. These results suggest that TMEM119 is useful in the treatment of gastric cancer.

TMEM2: A missing link in hyaluronan catabolism identified?

Hyaluronan (HA) is a glycosaminoglycan (GAG) composed of repeating disaccharide units of glucuronic acid and N-acetylglucosamine. HA is an extremely long, unbranched polymer, which often exceeds 10⁶ Da and sometimes reaches 10⁷ Da. A feature that epitomizes HA is its rapid turnover; one-third of the total body HA is turned over daily. The current model of HA catabolism postulates that high-molecular weight HA in the extracellular space is first cleaved into smaller fragments by a hyaluronidase(s) that resides at the cell surface, followed by internalization of fragments and their degradation into monosaccharides in lysosomes. Over the last decade, considerable research has shown that the HYAL family of hyaluronidases plays significant roles in HA catabolism. Nonetheless, the identity of a hyaluronidase responsible for the initial step of HA cleavage on the cell surface remains elusive, as biochemical and enzymological properties of HYAL proteins are not entirely consistent with those expected of cell surface hyaluronidases. Recent identification of transmembrane 2 (TMEM2) as a cell surface protein that possesses potent hyaluronidase activity suggests that it may be the "missing" cell surface hyaluronidase, and that novel models of HA catabolism should include this protein.

Genetic characterization of Polish ccRCC patients: somatic mutation analysis of PBRM1, BAP1 and KDMC5, genomic SNP array analysis in tumor biopsy and preliminary results of chromosome aberrations analysis in plasma cell free DNA

BACKGROUND

Mutation analysis and cytogenetic testing in clear cell renal cell carcinoma (ccRCC) is not yet implemented in a routine diagnostics of ccRCC.

MATERIAL AND METHODS

We characterized the chromosomal alterations in 83 ccRCC tumors from Polish patients using whole genome SNP genotyping assay. Moreover, the utility of next generation sequencing of cell free DNA (cfDNA) in patients plasma as a potential tool for non-invasive cytogenetic analysis was tested. Additionally, tumor specific somatic mutations in PBRM1, BAP1 and KDM5C were determined.

RESULTS

We confirmed a correlation between deletions at 9p and higher tumor size, and deletion of chromosome 20 and the survival time. In Fuhrman grade 1, only aberrations of 3p and 8p deletion, gain of 5q and 13q and gains of chromosome 7 and 16 were present. The number of aberrations increased with Fuhrman grade, all chromosomes displayed cytogenetic changes in G3 and G4. ccRCC specific chromosome aberrations were observed in cfDNA, although discrepancies were found between cfDNA and tumor samples. In total 12 common and 94 rare variants were detected in PBRM1, BAP1 and KDM5C, with four potentially pathogenic variants. We observed markedly lower mutation load in PBRM1.

CONCLUSIONS

Cytogenetic analysis of cfDNA may allow more accurate diagnosis of tumor aberrations and therefore the correlation between the chromosome aberrations in cfDNA and clinical outcome should be studied in larger cohorts. The functional studies on in BAP1, KDM5C, PBRM1 mutations in large, independent sample set would be necessary for the assessment of their prognostic and diagnostic potential.

Copy Number Variation of Immune-Related Genes and Their Association with Iodine in Adults with Autoimmune Thyroid Diseases

BACKGROUND

Autoimmune thyroid diseases (AITD) are complex conditions that are caused by an interaction between genetic susceptibility and environmental triggers. Iodine is already known to be an environmental trigger for AITD, but genes associated with susceptibility need to be further assessed. Therefore, the aims of this study were to assess the association between copy number variations (CNVs) and AITD, to identify genes related with susceptibility to AITD, and to investigate the interaction between iodine status and CNVs in the occurrence of AITD.

METHODS

Blood samples from 15 patients with AITD and 15 controls were assessed by chromosome microarray to identify candidate genes. The copy number of candidate genes and urinary iodine level was determined in adults from areas of different iodine statuses including 158 patients and 181 controls.

RESULTS

The immune-related genes, SIRPB1 and TMEM91, were selected as candidate genes. The distribution of SIRPB1 CNV in AITD patients and controls was significantly different and was considered a risk factor for AITD. There was no significant association between urinary iodine level and candidate gene CNVs.

CONCLUSION

SIRPB1 CNV and an excess of iodine were risk factors for AITD, but an association with the occurrence of AITD was not found.

TMEM207 hinders the tumour suppressor function of WWOX in oral squamous cell carcinoma

The WW domain‐containing oxidoreductase (WWOX) functions as a tumour suppressor in oral carcinogenesis. As aberrant TMEM207 expression may lead to tumour progression by hampering the tumour suppressor function of WWOX in various cancers, we explored the expression and pathobiological properties of TMEM207, focusing on the WWOX‐mediated regulation of the HIF‐1α pathway in oral squamous cell carcinoma (OSCC). TMEM207 immunoreactivity was detected in 40 of 90 OSCC samples but not in neighbouring non‐tumorous epithelial tissues. Moreover, TMEM207 expression was significantly correlated with lymph node metastasis and poor prognosis. An in situ proximal ligation assay demonstrated the colocalization of TMEM207 and WWOX in invasive OSCC cells, especially glycogen‐rich ones. Enforced expression of TMEM207 abrogated the binding of WWOX to HIF‐1α, increased HIF‐1α and GLUT‐1 expression, even under normoxic conditions, and promoted tumour growth in a xenoplant assay using SAS tongue squamous cancer cells. In contrast, TMEM207 knockdown decreased GLUT‐1 expression in two OSCC cell lines. As a whole, our findings indicate that the aberrant expression of TMEM207 contributes to tumour progression in OSCC, possibly via promoting aerobic glycolysis.

TMEM45B promotes proliferation, invasion and migration and inhibits apoptosis in pancreatic cancer cells

In the present study, we focused on the expression and biological functions of TMEM45B in pancreatic cancer tissues and cell lines. Real-time PCR and Western blotting were used to examine the expression levels of TMEM45B in pancreatic cancer tissues and cell lines. The functions of TMEM45B were evaluated using CCK-8, flow cytometry and transwell analysis. Our results showed that TMEM45B exhibited high expression in pancreatic cancer tissues and cell lines compared with the normal pancreatic tissues and cells. Using gene set enrichment analysis (GSEA), we found that TMEM45B may regulate multiple genes involved in the cell cycle and metastasis pathways. Downregulation of TMEM45B by RNA interference significantly reduced proliferation, invasion and migration of SW1990 and PANC-1 cells, accompanied by the induction of cell cycle arrest and apoptosis, whereas overexpression of TMEM45B promoted proliferation, invasion and migration of CFPAC-1 cells as well as apoptosis inhibition. Taken together, our study provides evidence that TMEM45B is an oncogene involved in the tumorigenesis of pancreatic cancer and may represent a new molecular target for pancreatic cancer treatment.

TMEM39A and Human Diseases: A Brief Review

Transmembrane Protein 39A (TMEM39A) is a member of TMEM family. The understanding about this protein is still limited. The earlier studies indicated that TMEM39A was a key mediator of autoimmune disease. TMEM39A seems to be involved in systemic lupus erythematosus and multiple sclerosis in numerous of populations. All of these works stop at insufficient information by using gene functioning methods such as: Genome-wide association studies (GWASs) and/or follow-up study. It is the fact that the less understood of TMEM39A actually is the attraction to the scientist in near future. In this review the current knowledge about TMEM39A and its possible roles in cell biology, physiology and pathology will be described.

Upregulation and biological function of transmembrane protein 119 in osteosarcoma

Osteosarcoma is suggested to be caused by genetic and molecular alterations that disrupt osteoblast differentiation. Recent studies have reported that transmembrane protein 119 (TMEM119) contributes to osteoblast differentiation and bone development. However, the level of TMEM119 expression and its roles in osteosarcoma have not yet been elucidated. In the present study, TMEM119 mRNA and protein expression was found to be up-regulated in osteosarcoma compared with normal bone cyst tissues. The level of TMEM119 protein expression was strongly associated with tumor size, clinical stage, distant metastasis and overall survival time. Moreover, gene set enrichment analysis (GSEA) of the Gene Expression Omnibus (GEO) GSE42352 dataset revealed TMEM119 expression in osteosarcoma tissues to be positively correlated with cell cycle, apoptosis, metastasis and TGF-β signaling. We then knocked down TMEM119 expression in U2OS and MG63 cells using small interfering RNA, which revealed that downregulation of TMEM119 could inhibit the proliferation of osteosarcoma cells by inducing cell cycle arrest in G0/G1 phase and apoptosis. We also found that TMEM119 knockdown significantly inhibited cell migration and invasion, and decreased the expression of TGF-β pathway-related factors (BMP2, BMP7 and TGF-β). TGF-β application rescued the inhibitory effects of TMEM119 knockdown on osteosarcoma cell migration and invasion. Further in vitro experiments with a TGF-β inhibitor (SB431542) or BMP inhibitor (dorsomorphin) suggested that TMEM119 significantly promotes cell migration and invasion, partly through TGF-β/BMP signaling. In conclusion, our data support the notion that TMEM119 contributes to the proliferation, migration and invasion of osteosarcoma cells, and functions as an oncogene in osteosarcoma.

Scanning indels in the 5q22.1 region and identification of the TMEM232 susceptibility gene that is associated with atopic dermatitis in the Chinese Han population

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease. The 5q22.1 region was found to have an association with AD in our previous genome-wide association study (GWAS).

OBJECTIVE

To identify the AD susceptibility gene in 5q22.1 and observe its expression in AD tissues.

METHODS

Suggestive indels from the GWAS data were genotyped in 3013 AD patients and 5075 controls from the Chinese Han population with the SequenomMassArray system. Association, Bayesian and bioinformatics analyses were used to identify possible causal indels and genes in the 5q22.1 region. Immunohistochemistry (IHC) was performed to observe protein expression in the tissues. PLINK 1.07 software was used for all statistical analyses.

RESULTS

The genotyping and association analysis showed that six deletions and four SNPs were associated with AD (P<0.005). The rs11357450 (P_combined=7.79E-04, OR=1.39, logBayes Factor=1.29) deletion located in TMEM232 was identified to be the strongest variant. Analysis of the genetic model revealed that the dominant model best described rs11357450 (P=1.96E-03, OR=1.22; 95% CI=1.07-1.37). IHC showed that the expression of TMEM232 decreased gradually from the granular layer to the basal layer in AD, but in normal tissues, this trend was reversed. Additionally, positive cytoplasm staining was found in lymphocytes around the blood vessels in AD.

CONCLUSIONS

The study indicates that TMEM232 in the 5q22.1 region is the causal gene for AD in the Chinese Han population.

A mammalian homolog of the zebrafish transmembrane protein 2 (TMEM2) is the long-sought-after cell-surface hyaluronidase

Hyaluronan (HA) is an extremely large polysaccharide (glycosaminoglycan) involved in many cellular functions. HA catabolism is thought to involve the initial cleavage of extracellular high-molecular-weight (HMW) HA into intermediate-size HA by an extracellular or cell-surface hyaluronidase, internalization of intermediate-size HA, and complete degradation into monosaccharides in lysosomes. Despite considerable research, the identity of the hyaluronidase responsible for the initial HA cleavage in the extracellular space remains elusive. HYAL1 and HYAL2 have properties more consistent with lysosomal hyaluronidases, whereas CEMIP/KIAA1199, a recently identified HA-binding molecule that has HA-degrading activity, requires the participation of the clathrin-coated pit pathway of live cells for HA degradation. Here we show that transmembrane protein 2 (TMEM2), a mammalian homolog of a protein playing a role in zebrafish endocardial cushion development, is a cell-surface hyaluronidase. Live immunostaining and surface biotinylation assays confirmed that mouse TMEM2 is expressed on the cell surface in a type II transmembrane topology. TMEM2 degraded HMW-HA into ∼5-kDa fragments but did not cleave chondroitin sulfate or dermatan sulfate, indicating its specificity to HA. The hyaluronidase activity of TMEM2 was Ca²⁺-dependent; the enzyme's pH optimum is around 6-7, and unlike CEMIP/KIAA1199, TMEM2 does not require the participation of live cells for its hyaluronidase activity. Moreover, TMEM2-expressing cells could eliminate HA immobilized on a glass surface in a contact-dependent manner. Together, these data suggest that TMEM2 is the long-sought-after hyaluronidase that cleaves extracellular HMW-HA into intermediate-size fragments before internalization and degradation in the lysosome.

Expression of TMEM207 in Colorectal Cancer: Relation between TMEM207 and Intelectin-1

Recent research advances highlighted an intestinal goblet cell-produced lectin, intelectin-1 (also known as omentin-1), as a tumor suppressor. One study indicated that downregulation of intelectin-1 may be related to the unfavorable prognosis among patients with colorectal carcinoma at an advanced stage. The present study was aimed at analyzing the expression of a hitherto uncharacterized transmembrane protein TMEM207 in colorectal carcinoma, and we found that the TMEM207 function is linked to intelectin-1 processing. With specific antibodies, TMEM207 immunoreactivity was detected in 38 of 216 colorectal cancer tissue samples. TMEM207 immunoreactivity correlated inversely with lymph node metastatic status (p < 0.01). TMEM207 expression significantly correlated with the mucinous phenotype of colorectal carcinoma. A coimmunoprecipitation assay revealed an interaction between intelectin-1 and TMEM207 in colorectal cancer cells. A proximal ligation assay indicated that intelectin-1 and TMEM207 were colocalized to the cytoplasm of the colorectal cancer cells. A small-interfering-RNA-mediated knockdown of TMEM207 increased polyubiquitination and proteasome degradation of intelectin-1 in cultured colorectal cancer cells and decreased intelectin-1 secretion. These findings indicate that a loss of TMEM207 expression leads to insufficient intelectin-1 production thus promoting colorectal carcinogenesis.