Past strategies and future directions for identifying AMP-activated protein kinase (AMPK) modulators

Abstract

AMP-activated protein kinase (AMPK) is a promising therapeutic target for cancer, type II diabetes, and other illnesses characterized by abnormal energy utilization. During the last decade, numerous labs have published a range of methods for identifying novel AMPK modulators. The current understanding of AMPK structure and regulation, however, has propelled a paradigm shift in which many researchers now consider ADP to be an additional regulatory nucleotide of AMPK. How can the AMPK community apply this new understanding of AMPK signaling to translational research? Recent insights into AMPK structure, regulation, and holoenzyme-sensitive signaling may provide the hindsight needed to clearly evaluate the strengths and weaknesses of past AMPK drug discovery efforts. Improving future strategies for AMPK drug discovery will require pairing the current understanding of AMPK signaling with improved experimental designs.

The double-edged sword of AMPK signaling in cancer and its therapeutic implications

“…Compound C was identified in a high-throughput kinase assay and is known to bind to the AMPKα subunit. However, many studies have shown that compound C can actually inhibit many other kinases as well as bone morphogenetic protein (BMP) receptor, indicating its promiscuity (Sinnett and Brenman 2014). Interestingly, a recent study showed that sunitinib, a multiple tyrosine kinase inhibitor that is used clinically against advanced renal cell carcinoma (RCC) and gastrointestinal stromal tumor (GIST), can directly inhibit AMPK activity by binding to the AMPKα subunit (Laderoute et al 2010).…”

IL‐7 suppresses macrophage autophagy and promotes liver pathology in Schistosoma japonicum‐infected mice

“…Our results in Figure A,B showed that SEA significantly suppressed, while IL‐7 significantly induced the activation of AMPK in purified PMΦs. Metformin (Met) and compound C were widely used as pharmacological activator or inhibitor of AMPK, respectively . Results showed that Met significantly decreased levels of LC3II expression (Figure C,D) and autophagosomes (Figures E and ) in all groups, including the significant decrease in the pro‐autophagic effect of SEA and the enhancement of the anti‐autophagic effect of IL‐7.…”

“…Metformin (Met) and compound C were widely used as pharmacological activator or inhibitor of AMPK, respectively. 26,27 Results showed that Met significantly decreased levels of LC3II expression ( Figure 5C To further confirm that AMPK is required for the anti-autophagic effects of IL-7, expression of AMPK was down-modulated using a-subunit-targeted siRNA. Immunoblot analysis revealed that siRNA targeting a-subunit dramatically reduced the total and phosphorylated AMPKa levels ( Figure 6A).…”

Promise and challenges for direct small molecule AMPK activators

“…AMPK signaling has attracted considerable attention within the past decades, owing to the capacity of pharmacological compounds (e.g., 5-aminoimidazole-4-carboxamide riboside" by as recently reported for the indirect AMPK activator R118 [69,70]. In addition, since some of the effects of indirect activators could be mediated through off-target effects independently of AMPK activation [71,72], intense interest has been focused on the development of more specific AMPK activators by using relevant screening systems for identifying compounds that interact directly to activate the AMPK heterotrimeric complex [73,74]. In 2006, highthroughput screen (HTS) efforts drove the discovery of the first non-nucleotide direct small molecule AMPK activator, A-592017, optimized to generate the more potent compound A-769662 [75] (Figure 3), demonstrating that AMPK activation with non-nucleotide ligands is possible.…”

“…Identification of novel 1-selective AMPK activators by virtual screening using molecular docking was recently reported [131] and holds promise on structure-based design of novel isoform-selective AMPK activators. In addition, improvement of screening methods based on the measure of direct allosteric activation, protection from dephosphorylation or a combination of both can contribute to fasten the identification of new hits [73,74,132]. Also, the use of specially-configured biosensors to monitor AMPK activation or conformational changes induced by ligands opens possibilities for identification and characterization of AMPK activators in cell-based assays [133].…”