Functional studies on native and mutated forms of perilipins. A role in protein kinase A-mediated lipolysis of triacylglycerols

J Biol Chem. 2003 Mar 7;278(10):8401-6. doi: 10.1074/jbc.M211005200. Epub 2002 Dec 10.

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.

MeSH terms

  • Animals
  • CHO Cells
  • Carrier Proteins
  • Cricetinae
  • Cricetulus
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Enzyme Activation
  • Fluorescent Antibody Technique
  • Mice
  • Mutagenesis
  • Perilipin-1
  • Phosphoproteins / genetics
  • Phosphoproteins / physiology*
  • Phosphorylation
  • Triglycerides / metabolism*

Substances

  • Carrier Proteins
  • Perilipin-1
  • Phosphoproteins
  • Triglycerides
  • Cyclic AMP-Dependent Protein Kinases