Direct effects of adipocyte lipolysis on AMPK through intracellular long-chain acyl-CoA signaling

Abstract

Long-chain acyl-CoAs (LC-acyl-CoAs) are important intermediary metabolites and are also thought to function as intracellular signaling molecules; however, the direct effects of LC-acyl-CoAs have been difficult to determine in real-time and dissociate from Protein Kinase A (PKA) signaling. Here, we examined the direct role of lipolysis in generating intracellular LC-acyl-CoAs and activating AMPK in white adipocytes by pharmacological activation of ABHD5 (also known as CGI-58), a lipase co-activator. Activation of lipolysis in 3T3-L1 adipocytes independent of PKA with synthetic ABHD5 ligands, resulted in greater activation of AMPK compared to receptor-mediated activation with isoproterenol, a β-adrenergic receptor agonist. Importantly, the effect of pharmacological activation of ABHD5 on AMPK activation was blocked by inhibiting ATGL, the rate-limiting enzyme for triacylglycerol hydrolysis. Utilizing a novel FRET sensor to detect intracellular LC-acyl-CoAs, we demonstrate that stimulation of lipolysis in 3T3-L1 adipocytes increased the production of LC-acyl-CoAs, an effect which was blocked by inhibition of ATGL. Moreover, ATGL inhibition blocked AMPKβ1 S108 phosphorylation, a site required for allosteric regulation. Increasing intracellular LC-acyl-CoAs by removal of BSA in the media and pharmacological inhibition of DGAT1 and 2 resulted in greater activation of AMPK. Finally, inhibiting LC-acyl-CoA generation reduced activation of AMPK; however, did not lower energy charge. Overall, results demonstrate that lipolysis in white adipocytes directly results in allosteric activation of AMPK through the generation of LC-acyl-CoAs.

Switchable Site-Selective Benzanilide C(sp2)-H Bromination via Promoter Regulation

“…More importantly, based on the diversity-oriented synthesis (DOS) strategy, C-C or C-N bond formation via cross coupling starting from brominated benzanilides will efficiently generate structurally diverse compound libraries, such as benzidine, phenylenediamine, etc. [ 7 , 8 , 9 , 10 , 11 , 12 ]. To date, various important small molecule modulators have been identified for “undruggable” targets from unbiased phenotypic screening of DOS-derived compound libraries [ 13 , 14 , 15 , 16 ].…”