TMEM176B Antibody

Introduction to TMEM176B

TMEM176B (also known as LR8) is a transmembrane protein belonging to the membrane-spanning 4A (MS4A) family of proteins. It was first discovered in human lung fibroblasts over two decades ago and has been associated with human small cell lung carcinoma . This protein plays a significant role in the regulation of dendritic cell maturation and antigen presentation . TMEM176B has emerged as an important immune checkpoint that curtails CD8+ T cell-mediated immunity by repressing inflammasome activation . Recent research has demonstrated that TMEM176B inhibits the activation of the NLRP3 inflammasome, establishing a link between adaptive and innate antitumor responses .

TMEM176B is characterized as an acid-sensitive cation channel expressed primarily in myeloid lineage immune cells, where it regulates dendritic cell maturation and antigen presentation . Higher TMEM176B expression has been observed in immature dendritic cells in allograft tolerance models, while lower expression has been reported in mature dendritic cells .

Protein Structure and Genetics

TMEM176B is encoded by the TMEM176B gene (Gene ID: 28959) and is characterized by the following properties:

The protein contains four transmembrane domains and an ITIM motif in its C terminus . As a member of the CD20-like MS4A family of proteins, TMEM176B shares structural similarities with other transmembrane proteins involved in immune regulation .

Expression Pattern

TMEM176B is expressed in various tissues and cell types, with particularly notable expression in:

• Lung and dermal fibroblasts

• Monocytes, macrophages, and CD11b+ dendritic cells

• Various cancer cell lines, including breast cancer models

• Immature dendritic cells

Types of TMEM176B Antibodies

Multiple types of TMEM176B antibodies are commercially available for research purposes:

These antibodies target different epitopes of TMEM176B, with some specifically designed to target the C-terminal region or other specific domains .

Applications of TMEM176B Antibodies

TMEM176B antibodies are utilized in multiple research applications:

Western Blotting (WB)

Antibodies detect TMEM176B protein expression in cell lysates and tissue samples, with observed molecular weights of approximately 31 kDa and 23 kDa . Positive WB results have been detected in A549 cells and human placenta tissue .

Immunohistochemistry (IHC)

Used to visualize TMEM176B expression patterns in tissue sections, enabling the study of its distribution in normal and pathological conditions .

Immunofluorescence (IF)

Allows for the subcellular localization of TMEM176B in cells and tissues .

ELISA

Enables quantitative measurement of TMEM176B in biological samples .

Therapeutic Research

Specially developed antibodies against TMEM176B have been used in experimental models to evaluate their potential as cancer therapeutics .

TMEM176B as an Inflammasome Regulator

One of the most significant discoveries about TMEM176B is its role as an inhibitor of the NLRP3 inflammasome . Research has demonstrated that:

• TMEM176B inhibits activation of the NLRP3 inflammasome by controlling cytosolic Ca2+ levels

• Bone marrow-derived dendritic cells from Tmem176b−/− mice exhibited increased secretion of IL1β and IL18, which are products of activated inflammasomes

• Tmem176b−/− mice showed increased NLRP3 inflammasome activation upon treatment with ATP, a known NLRP3 inflammasome activator

• TMEM176B-mediated inhibition of cytosolic Ca2+ accumulation ablates inflammasome-derived caspase-1/IL1β

Role in Dendritic Cell Maturation

TMEM176B is involved in the regulation of dendritic cell maturation and function:

• Higher TMEM176B expression is found in immature dendritic cells in allograft tolerance models

• TMEM176B may contribute to the suppressive function of dendritic cells by permitting the sodium counterflux required for endophagosome acidification

• It regulates dendritic cell maturation and antigen presentation processes

Signaling Pathway Involvement

TMEM176B participates in several important cellular signaling pathways:

• Regulates AKT/mTOR signaling in cancer cells

• Affects the NLRP3 inflammasome signaling pathway

• Influences the phosphoinositide 3-kinase pathway in cancer cells

• Impacts epithelial-mesenchymal transition (EMT) processes via the NLRP3 signaling pathway

Expression in Cancer

TMEM176B expression has been examined in various cancer types:

• TMEM176B is amplified in 6.5% of basal-like breast cancers, showing a copy number gain in 20.1% of cases compared with other breast cancer subtypes

• Expression is notably higher in the immunomodulatory subtype of triple-negative breast cancer (TNBC) compared with other subtypes

• TMEM176B is expressed in several cancer cell lines, including breast cancer, colon cancer, and lung cancer models

Impact on Cancer Cell Function

Research has revealed several ways in which TMEM176B affects cancer cell behavior:

• Silencing TMEM176B or inhibiting it with a therapeutic antibody impaired cell proliferation in vitro

• Overexpression of TMEM176B increased cell proliferation in vitro

• Syngeneic and xenograft tumor studies revealed attenuated growth of tumors with TMEM176B gene silencing compared with controls

• Short hairpin RNA targeting TMEM176B inhibited tumor metastasis and promoted the necrosis and degeneration of tumor cells

• TMEM176B promotes epithelial-mesenchymal transition via the NLRP3 signaling pathway in cancer cells

Role in Antitumor Immunity

TMEM176B has emerged as a significant regulator of antitumor immune responses:

• Disruption of TMEM176B contributes to CD8+ T cell-mediated tumor growth inhibition by unleashing inflammasome activation

• Tmem176b−/− mice inoculated with colon, lung, or thymic lymphoma cell lines showed higher survival and reduced tumor growth compared with wild-type mice

• Tumor-infiltrating CD8+ T cells from Tmem176b−/− mice showed greater proliferation compared to those from wild-type animals

• An increased effector T cell (CD8)/regulatory T cell (Foxp3) ratio was observed in Tmem176b−/− versus wild-type animals

Enhancement of Immune Checkpoint Therapy

One of the most promising aspects of TMEM176B research is its potential to enhance immune checkpoint therapy:

• Lack of Tmem176b enhances the antitumor activity of anti-CTLA-4 antibodies through mechanisms involving caspase-1/IL-1β activation

• Patients responding to checkpoint blockade therapies display an activated inflammasome signature

• BayK8644 has been identified as a potent TMEM176B inhibitor that promotes CD8+ T cell-mediated tumor control and reinforces the antitumor activity of both anti-CTLA-4 and anti-PD-1 antibodies

• Pharmacologic de-repression of the inflammasome by targeting TMEM176B may enhance the therapeutic efficacy of immune checkpoint blockers

Impact on Natural Killer Cell Function

TMEM176B also influences natural killer (NK) cell activity against cancer cells:

• Short hairpin RNA targeting TMEM176B increased the inhibition rate of interleukin-2-exposed NK cells on cancer cells

• TMEM176B affects NK cell activity through mechanisms that may involve the NLRP3 inflammasome pathway

Experimental Approaches

Researchers employ TMEM176B antibodies in various experimental approaches:

Gene Expression Analysis

• Western blot analysis using TMEM176B antibodies to evaluate protein expression levels in different cell lines and tissues

• Immunohistochemistry to examine TMEM176B expression patterns in tumor samples

Functional Studies

• Therapeutic antibody treatment to inhibit TMEM176B function in cancer cells

• Co-immunoprecipitation studies to identify protein-protein interactions involving TMEM176B

In Vivo Research

• Administration of anti-TMEM176B antibodies in animal models to evaluate effects on tumor growth

• Evaluation of therapeutic efficacy when combined with immune checkpoint inhibitors

Experimental Protocols

Typical protocols for TMEM176B antibody use include:

• For Western blot: Dilutions ranging from 1:200 to 1:1000, depending on the specific antibody

• For immunohistochemistry: Appropriate antigen retrieval and antibody-specific dilutions

• For cell proliferation studies with therapeutic antibodies: Addition of anti-TMEM176B antibody to cell medium (1:1000 dilution), refreshed daily, with cell counting after 120 hours

TMEM176B as a Therapeutic Target

The accumulated evidence suggests TMEM176B could be a promising therapeutic target:

• Inhibition of TMEM176B could enhance antitumor immunity and potentiate immune checkpoint therapy

• TMEM176B inhibitors like BayK8644 could be developed as adjuvants to existing cancer immunotherapies

• Anti-TMEM176B antibodies might serve as therapeutic agents in certain cancers

• Targeting the TMEM176B/NLRP3 axis may represent a novel therapeutic approach for cancer treatment

Biomarker Potential

TMEM176B expression or activity might serve as a biomarker:

• Patients responding to checkpoint blockade therapies display an activated inflammasome signature related to TMEM176B status

• TMEM176B expression levels in tumors might predict response to immunotherapy

• The Ala134Thr variant (rs2072443) in TMEM176B serves as a protector against colorectal cancer, linked to lower TMEM176B gene expression and heightened NLRP3 inflammasome in monocytes and dendritic cells