Regulation of M₃ Muscarinic Receptor Expression and Function by Transmembrane Protein 147

Abstract

The M 3 muscarinic acetylcholine receptor (M3R) regulates many fundamental physiological functions. To identify novel M3R-interacting proteins, we used a recently developed yeast two-hybrid screen (split ubiquitin method) to detect interactions among membrane proteins. This screen led to the identification of many novel M3R-associated proteins, including the putative membrane protein transmembrane protein 147 (Tmem147). The amino acid sequence of Tmem147 is highly conserved among mammals, but its physiological roles are unknown at present. We initially demonstrated that Tmem147 could be coimmunoprecipitated with M3Rs in cotransfected mammalian cells (COS-7 cells). Confocal imaging studies showed that Tmem147 was localized to endoplasmic reticulum (ER) membranes and that the Tmem147/ M3R interaction occurred in the ER of cotransfected COS-7 cells, resulting in impaired trafficking of the M3R to the cell surface. To study the role of Tmem147 in modulating M3R function in a more physiologically relevant setting, we carried out studies with H508 human colon cancer cells that endogenously express M3Rs and Tmem147. Treatment of H508 cells with carbachol, a hydrolytically stable acetylcholine analog, promoted H508 cell proliferation and activation of the mitogenic kinase, p90RSK. Small interfering RNA-mediated knockdown of Tmem147 expression significantly augmented the stimulatory effects of carbachol on H508 cell proliferation and p90RSK activation. These effects were associated with an increase in the density of cell surface M3Rs. Our data clearly indicate that Tmem147 represents a potent negative regulator of M3R function, most likely by interacting with M3Rs in an intracellular compartment (ER). These findings may lead to new strategies aimed at modulating M3R activity for therapeutic purposes.

Discovery of novel hepatocyte eQTLs in African Americans

“…Previously, a GWAS of platelet counts identified a risk variant, rs2251250, in chromosome 19 which was mapped to ATP4A [42]. Through our eQTL analysis, we found that rs2251250 was in LD with an overlapping eQTL, rs7599, for TMEM147, a transmembrane protein which regulates the M3 muscarinic acetylcholine receptor (M3R) encoded by CHRM3 [43], which in turn, was implicated in VTE in a previous GWAS study [44]. Thus, TMEM147 may serve as a potentially novel candidate gene for platelet count and VTE risk.…”

Sparse feature selection methods identify unexpected global cellular response to strontium-containing materials

“…These genes were transmembrane protein 147 (TMEM147), peripheral myelin protein 22 (PMP22), and farnesyl-diphosphate farnesyltransferase 1 (squalene synthase, FDFT1). TMEM147 is a transmembrane protein found exclusively in the endoplasmic reticulum that binds to cholesterol (16) and G protein-coupled receptors (GPCR) (17). PMP22 (also known as "GAS3") is a glycoprotein associated with lipid rafts (18) that modulates apoptosis, cell morphology, actin stress formation, and migration (19,20).…”

TMEM147 promotes hepatocellular carcinoma progress by inducing EGFR/MAPK activity

“…Neither TMEM147 upregulation nor downregulation affected EGFR mRNA levels; however, western blotting showed that TMEM147 overexpression promoted EGFR protein stability and expression, suggesting that TMEM147 increased EGFR expression levels via post-transcriptional regulation. TMEM147 is located in the Golgi and intracellular compartment and acts as a regulator mediating M3R trafficking and cellular location [21]. We therefore determined if TMEM147 could affect trafficking in the subcellular structure.…”

“…Transmembrane protein 147 (TMEM147), located in the intracellular compartment, acts as a regulator 4 mediating receptor trafficking and has been identified as a possible oncoprotein in colon cancer [20,21]. However, its function and molecular mechanism in HCC remain unknown.…”