Caveolin and MAL, two protein components of internal detergent-insoluble membranes, are in distinct lipid microenvironments in MDCK cells
Abstract
The MAL proteolipid and caveolin have been identified as components of internal detergent-insoluble membrane microdomains enriched in glycolipids and cholesterol. We have addressed the study of the glycolipid-enriched membranes in cells expressing endogenously only either MAL (Jurkat T cells) or caveolin (epithelial A498 cells) and in polarized MDCK cells which express both proteins simultaneously. Subcellular fractionation by centrifugation to equilibrium in sucrose gradients of Triton X-100 cell extracts from Jurkat and A498 cells revealed that MAL and caveolin are incorporated in detergent-insoluble buoyant membranes independently of the expression of each other and indicated the existence in these cells of insoluble membrane microdomains with either MAL or caveolin. Immunofluorescence analysis in MDCK cells indicated that both MAL and caveolin were located in the Golgi region, whereas caveolin was found in addition at the cell surface. Biochemical analysis in these cells revealed the existence of distinct membrane microenvironments differentially susceptible to detergent solubilization containing either internal MAL or internal plus surface caveolin. The observed heterogeneity within the internal glycolipid-enriched membran...Continue Reading
References
A glycophospholipid membrane anchor acts as an apical targeting signal in polarized epithelial cells
cDNA cloning and sequence of MAL, a hydrophobic protein associated with human T-cell differentiation
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Caveolins are small proteins with a hairpin loop conformation that are located in the plasma membrane of various cell types where they bind cholesterol and interact with receptors essential for several signal transduction pathways. Here is the latest research.