Perilipin promotes hormone-sensitive lipase-mediated adipocyte lipolysis via phosphorylation-dependent and -independent mechanisms.
Hormone-sensitive lipase (HSL) is the predominant lipase effector of catecholamine-stimulated lipolysis in adipocytes. HSL-dependent lipolysis in response to catecholamines is mediated by protein kinase A (PKA)-dependent phosphorylation of perilipin A (Peri A), an essential lipid droplet (LD)-associated protein. It is believed that perilipin phosphorylation is essential for the translocation of HSL from the cytosol to the LD, a key event in stimulated lipolysis. Using adipocytes retrovirally engineered from murine embryonic fibroblasts of perilipin null mice (Peri-/- MEF), we demonstrate by cell fractionation and confocal microscopy that up to 50% of cellular HSL is LD- associated in the basal state and that PKA- stimulated HSL translocation is fully supported by adenoviral expression of a mutant perilipin lacking all six PKA sites (Peri Adelta1-6). PKA-stimulated HSL translocation was confirmed in differentiated brown adipocytes from perilipin null mice expressing an adipose-specific Peri Adelta1-6 transgene. Thus, PKA-induced HSL translocation was independent of perilipin phosphorylation. However, Peri Adelta1-6 failed to enhance PKA- stimulated lipolysis in either MEF adipocytes or differentiated brown adipocytes. Thus, the lipolytic action(s) of HSL at the LD surface requires PKA-dependent perilipin phosphorylation. In Peri-/- MEF adipocytes, PKA activation significantly enhanced the amount of HSL that could be cross- linked to and co-immunoprecipitated with ectopic Peri A. Notably, this enhanced cross-linking was blunted in Peri-/- MEF adipocytes expressing Peri Adelta1-6. This suggests that PKA-dependent perilipin phosphorylation facilitates (either direct or indirect) perilipin interaction with LD- associated HSL. These results redefine and expand our understanding of how perilipin regulates HSL-mediated lipolysis in adipocytes.[1]References
- Perilipin promotes hormone-sensitive lipase-mediated adipocyte lipolysis via phosphorylation-dependent and -independent mechanisms. Miyoshi, H., Souza, S.C., Zhang, H.H., Strissel, K.J., Christoffolete, M.A., Kovsan, J., Rudich, A., Kraemer, F.B., Bianco, A.C., Obin, M.S., Greenberg, A.S. J. Biol. Chem. (2006) [Pubmed]
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