Liu Y, Jurczak MJ, Lear TB, Lin B, Larsen MB, Kennerdell JR, Chen Y, Huckestein BR, Nguyen MK, Tuncer F, Jiang Y, Monga SP, O’Donnell CP, Finkel T, Chen BB, Mallampalli RK. A Fbxo48 inhibitor prevents pAMPKα degradation and ameliorates insulin resistance. Nat Chem Biol. 2021 Jan 25. doi: 10.1038/s41589-020-00723-0. Epub ahead of print. PMID: 33495648.
The adenosine monophosphate (AMP)-activated protein kinase (Ampk) is a central regulator of metabolic pathways, and increasing Ampk activity has been considered to be an attractive therapeutic target. Here, we have identified an orphan ubiquitin E3 ligase subunit protein, Fbxo48, that targets the active, phosphorylated Ampkα (pAmpkα) for polyubiquitylation and proteasomal degradation. We have generated a novel Fbxo48 inhibitory compound, BC1618, whose potency in stimulating Ampk-dependent signaling greatly exceeds 5-aminoimidazole-4-carboxamide-1-β-ribofuranoside (AICAR) or metformin. This compound increases the biological activity of Ampk not by stimulating the activation of Ampk, but rather by preventing activated pAmpkα from Fbxo48-mediated degradation. We demonstrate that, consistent with augmenting Ampk activity, BC1618 promotes mitochondrial fission, facilitates autophagy and improves hepatic insulin sensitivity in high-fat-diet-induced obese mice. Hence, we provide a unique bioactive compound that inhibits pAmpkα disposal. Together, these results define a new pathway regulating Ampk biological activity and demonstrate the potential utility of modulating this pathway for therapeutic benefit.