Expression of a 64 kD adipocyte-specific plasma membrane protein in genetically lean but not obese porcine adipocytes

A monoclonal antibody (LA-1) to an adipocyte-specific plasma membrane protein (64 kD) was used to examine the differential expression of this protein in genetically lean and genetically obese pigs. Enzyme-linked immunosorbent assay (ELISA) implied the differential expression of the 64 kD protein in adipocyte plasma membranes having different genetic background. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of genetically lean, genetically obese, and contemporary subcutaneous adipocyte plasma membranes did not indicate any obvious qualitative differences in protein composition. Corresponding immunoblots utilizing LA-1 confirmed the presence of the 64 kD protein in contemporary and genetically lean adipocyte plasma membranes but absence in genetically obese adipocyte plasma membranes. LA-1 labelled intact adipocytes isolated from contemporary and genetically lean adipose tissue but did not react with isolated genetically obese adipocytes. The ability to bind to intact adipocytes indicates that the protein is exposed to the extracellular environment. The migration pattern of the protein was not affected by enzymatic deglycosylation by endoglycosidase-F suggesting that the protein is not highly, if at all, glycosylated. Presence of the 64 kD protein in genetically lean but not genetically obese adipocyte plasma membranes indicates the identification of a novel adipocyte-specific surface protein associated, either directly or secondary to the onset of obesity, with genetic predispositions for either genetically lean or obese body types in swine.