RESUMO
Fatty acyl-AMP ligases (FAALs) channelize fatty acids towards biosynthesis of virulent lipids in mycobacteria and other pharmaceutically or ecologically important polyketides and lipopeptides in other microbes. They do so by bypassing the ubiquitous coenzyme A-dependent activation and rely on the acyl carrier protein-tethered 4'-phosphopantetheine (holo-ACP). The molecular basis of how FAALs strictly reject chemically identical and abundant acceptors like coenzyme A (CoA) and accept holo-ACP unlike other members of the ANL superfamily remains elusive. We show that FAALs have plugged the promiscuous canonical CoA-binding pockets and utilize highly selective alternative binding sites. These alternative pockets can distinguish adenosine 3',5'-bisphosphate-containing CoA from holo-ACP and thus FAALs can distinguish between CoA and holo-ACP. These exclusive features helped identify the omnipresence of FAAL-like proteins and their emergence in plants, fungi, and animals with unconventional domain organizations. The universal distribution of FAALs suggests that they are parallelly evolved with FACLs for ensuring a CoA-independent activation and redirection of fatty acids towards lipidic metabolites.
Assuntos
Acil Coenzima A/metabolismo , Monofosfato de Adenosina/metabolismo , Proteínas de Bactérias/metabolismo , Ácidos Graxos/metabolismo , Ligases/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Sítios de Ligação , Ligases/química , Ligases/genética , Modelos Moleculares , Mutação , Ligação Proteica , Conformação Proteica , Relação Estrutura-AtividadeRESUMO
Pancreatic ß-cell failure is the key pathogenic element of the complex metabolic deterioration in type 2 diabetes (T2D); its underlying pathomechanism is still elusive. Here, we identify pleckstrin homology domain leucine-rich repeat protein phosphatases 1 and 2 (PHLPP1/2) as phosphatases whose upregulation leads to ß-cell failure in diabetes. PHLPP levels are highly elevated in metabolically stressed human and rodent diabetic ß-cells. Sustained hyper-activation of mechanistic target of rapamycin complex 1 (mTORC1) is the primary mechanism of the PHLPP upregulation linking chronic metabolic stress to ultimate ß-cell death. PHLPPs directly dephosphorylate and regulate activities of ß-cell survival-dependent kinases AKT and MST1, constituting a regulatory triangle loop to control ß-cell apoptosis. Genetic inhibition of PHLPPs markedly improves ß-cell survival and function in experimental models of diabetes in vitro, in vivo, and in primary human T2D islets. Our study presents PHLPPs as targets for functional regenerative therapy of pancreatic ß cells in diabetes.