Of the TRIM/RBCC family proteins taking part in a variety of cellular processes, 
TRIM50 is a stomach-specific member with no defined biological function. Our 
biochemical data demonstrated that TRIM50 is specifically expressed in gastric 
parietal cells and is predominantly localized in the tubulovesicular and 
canalicular membranes. In cultured cells ectopically expressing GFP-TRIM50, 
confocal microscopic imaging revealed dynamic movement of TRIM50-associated 
vesicles in a phosphoinositide 3-kinase-dependent manner. A protein overlay 
assay detected preferential binding of the PRY-SPRY domain from the TRIM50 
C-terminal region to phosphatidylinositol species, suggesting that TRIM50 is 
involved in vesicular dynamics by sensing the phosphorylated state of 
phosphoinositol lipids. Trim50 knock-out mice retained normal histology in the 
gastric mucosa but exhibited impaired secretion of gastric acid. In response to 
histamine, Trim50 knock-out parietal cells generated deranged canaliculi, 
swollen microvilli lacking actin filaments, and excess multilamellar membrane 
complexes. Therefore, TRIM50 seems to play an essential role in tubulovesicular 
dynamics, promoting the formation of sophisticated canaliculi and microvilli 
during acid secretion in parietal cells.