The autophagic inhibitor 3-methyladenine potently stimulates PKA-dependent lipolysis in adipocytes

Bradlee L. Heckmann, Xingyuan Yang, Xiaodong Zhang, Jun Liu

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

Background and Purpose: The class III PI3K inhibitor, 3-methyladenine (3-MA), is commonly used to selectively block autophagy. Recent findings suggest a strong relationship between autophagy and lipid turnover. Here, we explore the effect of 3-MA on adipocyte lipolysis. 0Assays were performed in 3T3-L1 cells. Cells were treated with 3-MA and wortmannin, a pan PI3K and autophagy inhibitor. Pharmacological and genetic manipulation of endogenous autophagic and lipolytic pathways was used to ascertain the contribution of 3-MA to the observed effects on lipolysis. Key Results: 3T3-L1 cells that were exposed to 3-MA showed a consistent increase in lipolysis, approximately 50% over basal levels. The effect of 3-MA was not secondary to autophagic inhibition as treatment of 3T3-L1 cells with wortmannin yielded no such changes. Dosing and time course experiments showed that 3-MA's ability to activate lipolysis was more sensitive than its inhibitory effect on autophagy. Knockdown of adipose triglyceride lipase (ATGL) negated the stimulatory effect of 3-MA by >90%, indicating that 3-MA enhanced ATGL-dependent hydrolysis of triacylglycerols. Additionally, the lipolytic effect of 3-MA was dependent on the activation of PKA and 3-MA induced a rapid and potent elevation of intracellular cAMP levels in adipocytes. Conclusions and Implications: Cumulatively, we show that 3-MA potently modulated a cellular mechanism and its underlying signalling pathways not associated with autophagy. Furthermore, we describe a novel stimulatory effect on a major signalling pathway. Our findings provide valuable information to studies employing 3-MA as a specific inhibitor for PI3K and autophagy.

Original languageEnglish (US)
Pages (from-to)163-171
Number of pages9
JournalBritish Journal of Pharmacology
Volume168
Issue number1
DOIs
StatePublished - Jan 2013

Keywords

  • 3-methyladenine
  • 3T3-L1
  • PI3-kinase
  • PKA
  • adipocyte
  • adipose tissue
  • autophagy
  • cAMP
  • lipolysis
  • triglyceride hydrolysis

ASJC Scopus subject areas

  • Pharmacology

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