Functional studies on native and mutated forms of perilipins. A role in protein kinase A-mediated lipolysis of triacylglycerols.
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.
Tansey
John T
JT
Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-8028, USA.
Huml
Anne M
AM
Vogt
Rainbow
R
Davis
Kathryn E
KE
Jones
Jennifer M
JM
Fraser
Kathryn A
KA
Brasaemle
Dawn L
DL
Kimmel
Alan R
AR
Londos
Constantine
C
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*
D002352:Carrier Proteins; D000070778:Perilipin-1; D010750:Phosphoproteins; D014280:Triglycerides; D017868:Cyclic AMP-Dependent Protein Kinases