Inhibition of AMP-Activated Protein Kinase at the Allosteric Drug-Binding Site Promotes Islet Insulin Release.

The AMP-activated protein kinase (AMPK) is a metabolic stress-sensing αßγ heterotrimer responsible for energy homeostasis. Pharmacological inhibition of AMPK is regarded as a therapeutic strategy in some disease settings including obesity and cancer; however, the broadly used direct AMPK inhibitor compound C suffers from poor selectivity. We have discovered a dihydroxyquinoline drug (MT47-100) with novel AMPK regulatory properties, being simultaneously a direct activator and inhibitor of AMPK complexes containing the ß1 or ß2 isoform, respectively. Allosteric inhibition by MT47-100 was dependent on the ß2 carbohydrate-binding module (CBM) and determined by three non-conserved CBM residues (Ile81, Phe91, Ile92), but was independent of ß2-Ser108 phosphorylation. Whereas MT47-100 regulation of total cellular AMPK activity was determined by ß1/ß2 expression ratio, MT47-100 augmented glucose-stimulated insulin secretion from isolated mouse pancreatic islets via a ß2-dependent mechanism. Our findings highlight the therapeutic potential of isoform-specific AMPK allosteric inhibitors.

A novel direct activator of AMPK inhibits prostate cancer growth by blocking lipogenesis.

5'AMP-activated kinase (AMPK) constitutes a hub for cellular metabolic and growth control, thus representing an ideal therapeutic target for prostate cancers (PCas) characterized by increased lipogenesis and activation of mTORC1 pathway. However, whether AMPK activation itself is sufficient to block cancer cell growth remains to be determined. A small molecule screening was performed and identified MT 63-78, a specific and potent direct AMPK activator. Here, we show that direct activation of AMPK inhibits PCa cell growth in androgen sensitive and castration resistant PCa (CRPC) models, induces mitotic arrest, and apoptosis. In vivo, AMPK activation is sufficient to reduce PCa growth, whereas the allelic loss of its catalytic subunits fosters PCa development. Importantly, despite mTORC1 blockade, the suppression of de novo lipogenesis is the underpinning mechanism responsible for AMPK-mediated PCa growth inhibition, suggesting AMPK as a therapeutic target especially for lipogenesis-driven PCas. Finally, we demonstrate that MT 63-78 enhances the growth inhibitory effect of AR signaling inhibitors MDV3100 and abiraterone. This study thus provides a rationale for their combined use in CRPC treatment.