Regulation of fsp27 protein stability by ampk and HSC70

Xiaodong Zhang, Bradlee L. Heckmann, Xitao Xie, Alicia M. Saarinen, Jun Liu

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

Fat-specific protein 27 (FSP27) plays a pivotal role in controlling the formation of large lipid droplet and energy metabolism. The cellular levels of FSP27 are tightly regulated through the proteasomal ubiquitin-mediated degradation. However, the upstream signals that trigger FSP27 degradation and the underlying mechanism(s) have yet to be identified. Here we show that AMP-activated protein kinase (AMPK) activation by AICAR (5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide) or phenformin induced the ubiquitination of FSP27 and promoted its degradation in 3T3-L1 adipocytes. The levels of FSP27 protein could be maintained by either knocking down AMPKa1 or blocking proteasomal pathway. Moreover, AICAR treatment induced multilocu-larization of LDs in 3T3-L1 adipocytes, reminiscent of the morphological changes in cells depleted of FSP27. Furthermore, mass spec-trometry-based proteomic analysis identified heat shock cognate 70 (HSC70) as a novel binding protein of FSP27. The specific interaction was confirmed by co-immunoprecipitation of both ectopically expressed and endogenous proteins. Importantly, knockdown of HSC70 by small interference RNA resulted in increased half-life of FSP27 in cells treated with a protein synthesis inhibitor cycloheximide (CHX) or AICAR. However, silencing of the E3 ubiquitin ligase CHIP (COOH terminus of HSC70-interacting protein) failed to alter the stability of FSP27 protein under both conditions. Taken together, our data indicate that AMPK is a negative regulator of FSP27 stability through the proteasomal ubiquitin-dependent protein catabolic process. Promotion of FSP27 degradation may be an important factor responsible for the beneficial effect of AMPK activators on energy metabolism.

Original languageEnglish (US)
Pages (from-to)E1047-E1056
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume307
Issue number11
DOIs
StatePublished - Dec 1 2014

Keywords

  • AMP-activated protein kinase
  • Fat-specific protein 27
  • Heat shock cognate 70

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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