Recombinant Mouse Transmembrane protein 147 (Tmem147)

Where is Tmem147 localized in cells and what expression patterns have been observed?

Tmem147 shows a dual localization pattern. Immunofluorescence assays demonstrate that Tmem147 localizes both to the cell membrane surface and within internal cellular compartments . While some studies initially reported Tmem147 as primarily localized to endoplasmic reticulum (ER) membranes in transfected COS-7 cells and HeLa cells , further research indicates that the localization may be cell-type dependent .

Flow cytometric analysis of goat peripheral blood mononuclear cells (PBMC) revealed that Tmem147 is expressed in 100% of B cells and monocytes, while approximately 3.8% of T cells did not express this protein . This differential expression pattern suggests potential specialized functions in different immune cell populations.

What protein complexes does Tmem147 participate in?

Tmem147 has been identified as a core component of the Nicalin-NOMO (Nodal modulator) complex . Similar to the assembly of γ-secretase, the formation of this complex appears to be hierarchical, beginning with the formation of a Nicalin-NOMO intermediate . Nicalin seems to be the limiting factor that regulates the assembly rate by stabilizing the other components, including Tmem147 .

Additionally, Tmem147 has been identified as part of a novel human translocon complex involved in multi-pass membrane protein biogenesis . This complex includes components that function in the endoplasmic reticulum for the proper assembly and insertion of multi-pass membrane proteins.

What role does Tmem147 play in immunological regulation?

Yeast two-hybrid (YTH) screening and co-immunoprecipitation assays have demonstrated that Tmem147 can bind to recombinant galectins (rHco-gal-m/f) from the parasite Haemonchus contortus . This interaction mediates several immunological functions:

• Cell proliferation: Knockdown of the tmem147 gene using RNA interference significantly reversed the inhibitory effect of rHco-gal-m on PBMC proliferation, indicating that Tmem147 mediates the suppression of immune cell proliferation by parasite galectins .

• Apoptosis regulation: The interaction between rHco-gal-m and Tmem147 influences cell apoptosis pathways in immune cells .

• Cytokine expression: Tmem147 mediates the regulation of cytokine production, particularly interleukin-10 (IL-10) and transforming growth factor-β1 (TGF-β1), which are important immunoregulatory molecules .

• Phagocytosis and nitric oxide production: Together with another transmembrane protein (TMEM63A), Tmem147 participates in regulating phagocytosis and nitric oxide production in immune cells exposed to parasite galectins .

These findings suggest that Tmem147 plays a crucial role in host-parasite interactions and may be involved in immune evasion mechanisms employed by nematode parasites.

How does Tmem147 contribute to multi-pass membrane protein biogenesis?

Recent structural studies have identified Tmem147 as a component of a specialized endoplasmic reticulum (ER) translocon complex dedicated to multi-pass membrane protein biogenesis . In this complex, Tmem147 works alongside other components including Sec61, Nicalin, TMCO1, and CCDC47.

The structure of this complex has been analyzed using cryo-electron microscopy, with homology models for Tmem147 generated using the γ-secretase subunits as templates . This structural arrangement suggests that Tmem147 assists in the proper folding and insertion of complex membrane proteins with multiple transmembrane domains.

The association of Tmem147 with both the Nicalin-NOMO complex and the ER translocon indicates it may serve as a bridge between protein quality control mechanisms and membrane protein synthesis and insertion pathways. This role is particularly important for maintaining cellular proteostasis and ensuring proper membrane protein topology.

What phenotypic effects have been observed with Tmem147 knockdown or overexpression?

RNA interference (RNAi) experiments targeting the tmem147 gene have revealed several phenotypic effects:

• Reversed immunosuppression: Knockdown of Tmem147 significantly counteracted the inhibitory effects of parasite galectins on immune cell proliferation .

• Modified cytokine expression: Tmem147 knockdown altered the expression profiles of IL-10 and TGF-β1, suggesting its role in regulating anti-inflammatory responses .

• Altered cellular processes: Tmem147 knockdown affected phagocytosis and nitric oxide production in goat PBMC, indicating its involvement in innate immune functions .

What are the optimal conditions for expressing and purifying recombinant Tmem147?

Recombinant mouse Tmem147 can be expressed using several systems, each with specific advantages:

For purification, protein A chromatography is commonly used for antibody-tagged constructs , while His-tagged proteins can be purified via nickel affinity chromatography. The recommended reconstitution protocol involves:

• Centrifuging the vial at 5,000×g for 5 minutes

• Adding sterile deionized water to a concentration of 0.1-1.0 mg/mL

• Incubating for 10 minutes at room temperature

• Brief vortexing followed by a quick spin to concentrate the liquid

• Adding glycerol to a final concentration of 50% for long-term storage

To maintain stability, it's advisable to avoid repeated freeze-thaw cycles and store working aliquots at 4°C for up to one week .

What detection methods and tools are available for studying Tmem147?

Several detection tools and methods have been developed for studying Tmem147:

• Antibodies: Available antibodies include:

  • Polyclonal antibodies recognizing amino acids 51-150

  • Antibodies with various conjugates including Biotin, AbBy Fluor® 350, 555, 594, 647, 680, and 750

  • Antibodies suitable for Western Blotting, Immunofluorescence, ELISA, and Immunohistochemistry

• Expression constructs: Tmem147 can be expressed with various tags:

  • His-tagged constructs

  • Strep-tagged constructs

  • GFP-tagged lentiviral expression systems

• Application-specific protocols: For optimal results, the following dilutions are recommended:

  • Western Blotting: 1:300-5000

  • ELISA: 1:500-1000

  • IHC-P (Paraffin): 1:200-400

  • IHC-F (Frozen): 1:100-500

  • IF (Immunofluorescence): 1:50-200

What are the most effective approaches for studying Tmem147-protein interactions?

Several complementary methods have proven effective for investigating Tmem147 interactions:

• Yeast Two-Hybrid (YTH) Screening: This approach has successfully identified binding partners for Tmem147, including galectins from Haemonchus contortus . YTH is particularly useful for initial discovery of protein-protein interactions.

• Co-immunoprecipitation (co-IP): Both forward and reverse co-IP experiments have been used to validate Tmem147 interactions. The protocol involves:

  • Stimulating cells with the potential binding partner

  • Cell lysis and preclearing of lysates

  • Immunoprecipitation with specific antibodies

  • Analysis by immunoblotting

• Confocal microscopy: Immunofluorescence assays using confocal imaging have been employed to study the co-localization of Tmem147 with binding partners in intact and permeabilized cells .

• RNA interference (RNAi): Knockdown of the tmem147 gene using siRNA has been instrumental in determining the functional significance of Tmem147 interactions, revealing which cellular processes are mediated by specific protein-protein interactions .

• Structural biology approaches: For detailed interaction mechanisms, cryo-electron microscopy has been used to analyze the structure of Tmem147 within protein complexes, utilizing homology models based on related proteins .

What cell and animal models are most appropriate for studying Tmem147 function?

Based on the available research, several models have proven valuable for investigating Tmem147 function:

• Cell models:

  • HEK293T cells: Used for initial characterization and protein expression

  • Goat peripheral blood mononuclear cells (PBMC): Particularly useful for studying immunological functions of Tmem147 in the context of parasite infections

  • COS-7 cells and HeLa cells: Used for subcellular localization studies

• Animal models:

  • Mouse models: Given the high conservation of Tmem147 across species, mouse models are appropriate for in vivo studies

  • Zebrafish (Danio rerio): Used for studying Tmem147 during early development

For functional studies, particularly those investigating immune regulation, primary immune cells like PBMC offer advantages over cell lines as they better represent physiological conditions. Flow cytometry can be used to study Tmem147 expression in specific immune cell subpopulations (T cells, B cells, and monocytes) .

When designing knockdown experiments, it's important to note that Tmem147 appears to have specialized functions in different cellular contexts, so the choice of model should align with the specific aspect of Tmem147 biology being investigated.

What are the key unanswered questions about Tmem147 function?

Despite significant progress in understanding Tmem147, several important questions remain:

• The precise molecular mechanism by which Tmem147 contributes to multi-pass membrane protein biogenesis remains to be fully elucidated.

• The broader physiological significance of Tmem147 beyond its identified roles in immune regulation and membrane protein assembly warrants further investigation.

• The potential involvement of Tmem147 in disease processes, particularly those related to membrane protein misfolding or immune dysregulation, represents an important area for future research.

• The specific functions of Tmem147 in the TMEM147-negative T cell subpopulation (approximately 3.8% of T cells) remain to be determined and could reveal specialized immunological roles .