Submitted to: American Diabetes Association Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/1/2001
Publication Date: 2/1/2002
Citation: ZHANG, H.H., SOUZA, S.C., MULIRO, K., GREENBERG, A.S. THE FUNCTIONAL DOMAIN THAT TARGETS PERILIPINS TO LIPID DROPLETS AND REGULATES LIPOLYSIS. AMERICAN DIABETES ASSOCIATION MEETING. 2002. Interpretive Summary:
Technical Abstract: Perilipins are phosphoproteins that localize at the surface of intracellular lipid (triacylglycerol) droplets in adipocytes. They regulate lipolysis and triacylglycerol (TG) storage by coating lipid droplets, thereby reducing the access of lipases, including hormone-sensitive lipase (HSL). Phosphorylation of perilipins in response to lipolytic hormones leads to their disassociation from lipid droplets and lipase-mediated lipolysis. To determine the functional domain(s) that target perilipins to lipid droplets and regulate lipid metabolism, adenoviruses encoding full length and truncated mutants of mouse perilipins were constructed and transduced to NIH 3T3 fibroblasts, which lack perilipins but overexpress acyl Co-A synthetase1 (ACS1) and fatty acid transport protein 1 (FATP1). ACS1/FATP1 expression results in increased TG accumulation in response to fatty acid loading. Subcellular localization of perilipin mutants was examined by double immunofluorescence staining for perilipin/lipid and by confocal microscopy. The ability of perilipin mutants to protect stored TG from soluble lipases was determined by quantifying intracellular TG content using lipid extraction and thin layer chromatography. Perilipin A (517 amino acids, 517 AA) and perilipin B (422 AA) share a common N-terminal region of 405 AA. Ectopic expression of perilipin A and B, which localize on lipid droplets, increased triacylglycerol storage by ~ 2.4 and ~ 1.8 fold respectively. Truncations of perilipin from the carboxy-terminus to 300 AA and 250 AA did not affect association with lipid droplets, and expression of the mutants increased TG storage by ~ 1.7 fold. Further truncations to 200 AA and 142 AA led to the disassociation of the protein from lipid droplets, and expression of these truncated mutants had no detectable effect on TG storage. These findings indicate that the structural region between 200AA and 250 AA may be the functional domain that targets perilipin to lipid droplets and regulates lipolysis.