title: Perilipin promotes hormone-sensitive lipase-mediated adipocyte lipolysis via phosphorylation-dependent and -independent mechanisms.
abstract: 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.
authors.affiliation: Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts 02111, USA.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Miyoshi
authors.forename: Sandra C
authors.initials: SC
authors.lastname: Souza
authors.forename: Hui-Hong
authors.initials: HH
authors.lastname: Zhang
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Strissel
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Christoffolete
authors.forename: Julia
authors.initials: J
authors.lastname: Kovsan
authors.forename: Assaf
authors.initials: A
authors.lastname: Rudich
authors.forename: Fredric B
authors.initials: FB
authors.lastname: Kraemer
authors.forename: Antonio C
authors.initials: AC
authors.lastname: Bianco
authors.forename: Martin S
authors.initials: MS
authors.lastname: Obin
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Greenberg
mesh_terms: D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D008066:Lipolysis / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D000070778:Perilipin-1; D010750:Phosphoproteins / Q000502:physiology*; D010766:Phosphorylation; D002787:Sterol Esterase / Q000502:physiology*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D017931:DNA Primers; D000070778:Perilipin-1; D010750:Phosphoproteins; D017868:Cyclic AMP-Dependent Protein Kinases; D002787:Sterol Esterase