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

Br J Pharmacol. 2013 Jan;168(1):163-71. doi: 10.1111/j.1476-5381.2012.02110.x.


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. EXPERIMENTAL APPROACH Assays 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3-L1 Cells
  • Adenine / analogs & derivatives*
  • Adenine / metabolism
  • Adenine / pharmacology
  • Adipocytes / metabolism*
  • Androstadienes / pharmacology
  • Animals
  • Autophagy / drug effects*
  • Hydrolysis
  • Lipase / metabolism
  • Lipolysis / physiology*
  • Mice
  • Phosphoinositide-3 Kinase Inhibitors*
  • RNA, Small Interfering / metabolism
  • Signal Transduction
  • Sterol Esterase / metabolism
  • Triglycerides / metabolism
  • Wortmannin


  • Androstadienes
  • Phosphoinositide-3 Kinase Inhibitors
  • RNA, Small Interfering
  • Triglycerides
  • 3-methyladenine
  • Sterol Esterase
  • Lipase
  • Adenine
  • Wortmannin