Recombinant Human Transmembrane protein 204 (TMEM204)

What is the basic structure of TMEM204?

TMEM204 (Transmembrane Protein 204) is a member of the TMEM family that contains four predicted transmembrane domains and a C-terminal protein-protein interaction domain. It functions as a novel hypoxia-regulated tetramer adhesion junction protein . The protein's structure facilitates its role in cell adhesion, cell bypass permeability, and angiogenesis processes .

What are the primary biological functions of TMEM204?

TMEM204 primarily regulates cell function and angiogenesis. Research has shown that TMEM204 expression in endothelial-specific transcripts in developing endothelial cells was significantly higher than in normal endothelial cells in control groups, indicating its crucial role in adult angiogenesis . Additionally, TMEM204 functions as a regulator of cell adhesion and cell bypass permeability, making it important in tissue development and maintenance .

How does TMEM204 expression differ between normal and cancer tissues?

TMEM204 shows varied expression patterns across different cancers. According to Oncomine database analysis, TMEM204 expression is higher in breast cancer, melanoma, and pancreatic cancer compared to normal tissues, while it shows lower expression in bladder cancer, kidney cancer, lung cancer, and myeloma . In TIMER2.0 database analysis, TMEM204 was highly expressed in cholangiocarcinoma (CHOL), glioblastoma multiforme (GBM), head and neck squamous cell carcinoma (HNSC), kidney renal clear cell carcinoma (KIRC), and liver hepatocellular carcinoma (LIHC) .

What regulates TMEM204 expression in cancer tissues?

DNA methylation appears to be a significant regulator of TMEM204 expression. In liver hepatocellular carcinoma (LIHC), the promoter methylation level of TMEM204 is higher than in normal tissues . Interestingly, this high promoter DNA methylation correlates with high expression of TMEM204 in LIHC, suggesting a complex regulatory mechanism . Additionally, meta array and methylation-specific PCR analysis revealed that 95% of TMEM204 in pancreatic cancer cell lines (AsPC-1, Mia PaCa-2, and PANC-1) was methylated .

How does TMEM204 expression correlate with immune cell infiltration in cancer?

TMEM204 expression significantly correlates with immune cell infiltration, particularly in liver hepatocellular carcinoma (LIHC). The TIMER2.0 database analysis revealed significant correlations between TMEM204 expression and the infiltration of:

• CD8+ T cells (Rho=0.202, P=1.58e-04)

• CD4+ T cells (Rho=0.256, P=1.39e-06)

• Macrophages (Rho=0.203, P=1.48e-04)

• Neutrophils (Rho=0.157, P=3.56e-03)

• Myeloid dendritic cells (Rho=0.193, P=3.04e-04)

This suggests TMEM204 may play a role in modulating the tumor immune microenvironment, which could contribute to its prognostic significance in LIHC.

What bioinformatic tools are recommended for analyzing TMEM204 expression and function?

Several bioinformatic tools and databases have proven valuable for TMEM204 research:

• Oncomine: Useful for analyzing differential expression between tumor and normal tissues across multiple cancer types

• TIMER2.0 (Tumor Immune Estimation Resource): Valuable for studying the correlation between TMEM204 expression and immune cell infiltration in tumors

• GEPIA2 (Gene Expression Profile Interaction Analysis 2): Provides expression profiles and survival analysis for TMEM204 across different cancer types

• UALCAN: Offers in-depth analysis of TCGA gene expression data, including the pathologic characteristics of different tumor subgroups and methylation patterns

• Oncolnc: Generates Kaplan-Meier graphs to analyze survival information related to TMEM204 expression

• cBioPortal: Enables visualization of cancer genomics data, including TMEM204 mutations and their effect on survival

• STRING: Useful for constructing protein-protein interaction networks involving TMEM204

• WebGestalt: Facilitates functional enrichment analysis to discover biological pathways associated with TMEM204

What experimental approaches are recommended for validating TMEM204 as a potential biomarker?

To validate TMEM204 as a potential biomarker, researchers should consider a multi-faceted approach:

• Expression validation: Use immunohistochemistry and Western blotting to confirm TMEM204 protein expression in clinical samples

• Methylation analysis: Employ methylation-specific PCR or bisulfite sequencing to analyze the methylation status of TMEM204 promoter in different cancer types

• Prognostic validation: Conduct large-scale retrospective and prospective clinical studies to confirm the association between TMEM204 expression and patient outcomes

• Functional studies: Perform gain-of-function and loss-of-function experiments using cell lines to determine the molecular mechanisms through which TMEM204 affects cancer progression

• Immune correlation studies: Use flow cytometry and multiplex immunofluorescence to verify the correlation between TMEM204 expression and immune cell infiltration observed in bioinformatic analyses

What signaling pathways are associated with TMEM204 function in cancer?

KEGG pathway analysis has implicated two major signaling pathways associated with TMEM204:

• p53 signaling pathway: This tumor suppressor pathway regulates cell cycle arrest, apoptosis, senescence, and DNA repair. The association with TMEM204 suggests it may play a role in p53-mediated tumor suppression mechanisms .

• Fanconi anemia pathway: This pathway is involved in DNA repair, particularly for interstrand crosslinks. Its association with TMEM204 suggests a potential role in maintaining genomic stability .

Further investigation of these pathways could provide insights into the molecular mechanisms through which TMEM204 affects cancer progression and patient outcomes.

How can protein-protein interaction (PPI) networks help understand TMEM204 function?

PPI network analysis conducted through the STRING database revealed 20 proteins closely related to TMEM204 . This network analysis can help researchers:

• Identify functional partners that interact with TMEM204

• Discover biological processes and pathways in which TMEM204 participates

• Generate hypotheses about the molecular mechanisms through which TMEM204 influences cancer development and progression

• Identify potential therapeutic targets that could modulate TMEM204 activity

The PPI network showed connections through text-mining (yellow links), co-expression (black links), and experimentally determined interactions (purple links), providing a comprehensive view of TMEM204's functional relationships .

What are the common genetic alterations of TMEM204 in cancer?

Analysis using the cBioPortal database revealed that the mutation rate of TMEM204 in liver hepatocellular carcinoma (LIHC) was 0.5% . The alterations observed include:

• Missense mutations: One missense mutation was identified in hepatocellular carcinoma

• Deep deletions: These account for the majority of TMEM204 alterations in LIHC

How should researchers approach the functional characterization of TMEM204 variants?

To functionally characterize TMEM204 variants, researchers should:

• Generate variant constructs: Create expression vectors containing wild-type and mutant TMEM204 sequences

• Perform cellular localization studies: Use immunofluorescence microscopy to determine if mutations affect the subcellular localization of TMEM204

• Assess protein stability: Measure protein half-life to determine if mutations affect TMEM204 stability

• Analyze signaling effects: Examine the impact of TMEM204 variants on p53 and Fanconi anemia pathway signaling

• Conduct phenotypic assays: Assess the effects of TMEM204 variants on cell proliferation, migration, invasion, and angiogenesis

• Perform animal studies: Generate mouse models expressing TMEM204 variants to evaluate their effects on tumorigenesis in vivo