title: Functional studies on native and mutated forms of perilipins. A role in protein kinase A-mediated lipolysis of triacylglycerols.
abstract: Perilipin A coats the lipid storage droplets in adipocytes and is polyphosphorylated by protein kinase A (PKA); the fact that PKA activates lipolysis in adipocytes suggests a role for perilipins in this process. To assess whether perilipins participate directly in PKA-mediated lipolysis, we have expressed constructs coding for native and mutated forms of the two major splice variants of the perilipin gene, perilipins A and B, in Chinese hamster ovary fibroblasts. Perilipins localize to lipid droplet surfaces and displace the adipose differentiation-related protein that normally coats the droplets in these cells. Perilipin A inhibits triacylglycerol hydrolysis by 87% when PKA is quiescent, but activation of PKA and phosphorylation of perilipin A engenders a 7-fold lipolytic activation. Mutation of PKA sites within the N-terminal region of perilipin abrogates the PKA-mediated lipolytic response. In contrast, perilipin B exerts only minimal protection against lipolysis and is unresponsive to PKA activation. Since Chinese hamster ovary cells contain no PKA-activated lipase, we conclude that the expression of perilipin A alone is sufficient to confer PKA-mediated lipolysis in these cells. Moreover, the data indicate that the unique C-terminal portion of perilipin A is responsible for its protection against lipolysis and that phosphorylation at the N-terminal PKA sites attenuates this protective effect.
authors.affiliation: Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-8028, USA.
authors.forename: John T
authors.initials: JT
authors.lastname: Tansey
authors.forename: Anne M
authors.initials: AM
authors.lastname: Huml
authors.forename: Rainbow
authors.initials: R
authors.lastname: Vogt
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Davis
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Jones
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Fraser
authors.forename: Dawn L
authors.initials: DL
authors.lastname: Brasaemle
authors.forename: Alan R
authors.initials: AR
authors.lastname: Kimmel
authors.forename: Constantine
authors.initials: C
authors.lastname: Londos
mesh_terms: D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins; D006224:Cricetinae; D003412:Cricetulus; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D005455:Fluorescent Antibody Technique; D051379:Mice; D016296:Mutagenesis; D000070778:Perilipin-1; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D000070778:Perilipin-1; D010750:Phosphoproteins; D014280:Triglycerides; D017868:Cyclic AMP-Dependent Protein Kinases