GSK621

GSK621 is a specific and potent agonist of AMP-activated protein kinase (AMPK) with IC50 values ranging from 13 to 30 µM for cell lines [1].

AMPK is a heterotrimeric serine/threonine kinase. It is a sensor of cellular energy. It regulates multiple cellular metabolic pathways. Activation of AMPK inactivates the phosphorylation of acetyl-Coa carboxylase (ACC), and hence inhibits the biosynthesis of fatty acid. Activation of AMPK also inhibits protein synthesis that is dependent on mammalian target of rapamycin complex 1. AMPK also promotes autophagy, fatty acid oxidation, glucose uptake and glycolysis [1].

In cells, at the opposite, GSK621 showed more potency to activate AMPK than A-769662, based on the ACC phosphorylation level. In MOLM-14 cells, 200 µM A-769662 is just as potent as 30 µM GSK621 to induce the phosphorylation of ULK1 (S555) and ACC (S79), two direct AMPK substrates. In AML cell lines (OCI-AML3, HL-60 and MOLM-14) and primary AML samples, the phosphorylation at AMPKα T172, a marker of AMPK activation, was markedly increased, and the phosphorylation of ULK1 (S555) and ACC (S79) was stimulated by GSK621 [1].

In animals with xenograft MOLM-14 cells, intraperitoneal injection of GSK621 at 30 mg/kg twice daily reduced leukemia growth and markedly extended survival compared to treatment with 10 mg/kg GSK621 twice daily or vehicle. These results correlated to increased AMPK activity indicated by the induction of apoptosis and increased ACC S79 phosphorylation [1].

Reference:
[1].  Sujobert P, Poulain L, Paubelle E, et al. Co-activation of AMPK and mTORC1 induces cytotoxicity in acute myeloid leukemia. Cell reports, 2015, 11(9): 1446-1457.

GSK621 Targets Glioma Cells via Activating AMP-Activated Protein Kinase Signalings.[Pubmed:27532105]

PLoS One. 2016 Aug 17;11(8):e0161017.

Here, we studied the anti-glioma cell activity by a novel AMP-activated protein kinase (AMPK) activator GSK621. We showed that GSK621 was cytotoxic to human glioma cells (U87MG and U251MG lines), possibly via provoking caspase-dependent apoptotic cell death. Its cytotoxicity was alleviated by caspase inhibitors. GSK621 activated AMPK to inhibit mammalian target of rapamycin (mTOR) and downregulate Tetraspanin 8 (Tspan8) in glioma cells. AMPK inhibition, through shRNA knockdown of AMPKalpha or introduction of a dominant negative (T172A) AMPKalpha, almost reversed GSK621-induced AMPK activation, mTOR inhibition and Tspan8 degradation. Consequently, GSK621's cytotoxicity in glioma cells was also significantly attenuated by AMPKalpha knockdown or mutation. Further studies showed that GSK621, at a relatively low concentration, significantly potentiated temozolomide (TMZ)'s sensitivity and lethality against glioma cells. We summarized that GSK621 inhibits human glioma cells possibly via activating AMPK signaling. This novel AMPK activator could be a novel and promising anti-glioma cell agent.

AMPK activation by GSK621 inhibits human melanoma cells in vitro and in vivo.[Pubmed:27751856]

Biochem Biophys Res Commun. 2016 Nov 25;480(4):515-521.

Recent studies suggest that forced activation of AMP-activated protein kinase (AMPK) could inhibit melanoma cell proliferation. In this report, we evaluated the anti-melanoma cell activity by a novel small-molecular AMPK activator, GSK621. Treatment of GSK621 decreased survival and proliferation of human melanoma cells (A375, WM-115 and SK-Mel-2 lines), which was accompanied by activation of caspase-3/-9 and apoptosis. Reversely, caspase inhibitors attenuated GSK621-induced cytotoxicity against melanoma cells. Significantly, GSK621 was more potent than other AMPK activators (A769662, Compound 13 and AICAR) in inhibiting melanoma cells. Intriguingly, same GSK621 treatment was non-cytotoxic or pro-apoptotic against human melanocytes. Molecularly, we showed that activation of AMPK mediated GSK621's activity against melanoma cells. AMPKalpha1 shRNA knockdown or dominant negative mutation (T172A) dramatically attenuated GSK621-induced melanoma cell lethality. Further studies revealed that MEK-ERK activation might be the primary resistance factor of GSK621. MEK-ERK inhibition, either genetically or pharmacologically, significantly sensitized melanoma cells to GSK-621. Remarkably, intraperitoneal (i.p.) injection of GSK621 inhibited A375 tumor growth in SCID mice. Co-administration of MEK-ERK inhibitor MEK162 further sensitized GSK621-induced anti-A375 tumor activity in vivo. Together, the results imply that targeted activation of AMPK by GSK621 inhibits melanoma cell survival and proliferation. MEK-ERK inhibition may further sensitize GSK621's anti-melanoma cell activity in vitro and in vivo.

GSK621 activates AMPK signaling to inhibit LPS-induced TNFalpha production.[Pubmed:27712936]

Biochem Biophys Res Commun. 2016 Nov 18;480(3):289-295.

LPS stimulation in macrophages/monocytes induces TNFalpha production. We here tested the potential effect of GSK621, a novel AMP-activated protein kinase (AMPK) activator, against the process. In RAW264.7 macrophages, murine bone marrow-derived macrophages (BMDMs), and chronic obstructive pulmonary disease (COPD) patients' monocytes, GSK621 significantly inhibited LPS-induced TNFalpha protein secretion and mRNA synthesis. Inhibition of AMPK, through AMPKalpha shRNA knockdown or dominant negative mutation (T172A), almost abolished GSK621's suppression on TNFalpha in RAW264.7 cells. Reversely, forced-expression of a constitutively-active AMPKalpha (T172D) mimicked GSK621 actions and reduced LPS-induced TNFalpha production. Molecularly, GSK621 suppressed LPS-induced reactive oxygen species (ROS) production and nuclear factor kappa B (NFkappaB) activation. In vivo, GSK621 oral administration inhibited LPS-induced TNFalpha production and endotoxin shock in mice. In summary, GSK621 activates AMPK signaling to inhibit LPS-induced TNFalpha production in macrophages/monocytes.

Targeted activation of AMPK by GSK621 ameliorates H2O2-induced damages in osteoblasts.[Pubmed:28060740]

Oncotarget. 2017 Feb 7;8(6):10543-10552.

GSK621 is a novel AMP-activated protein kinase (AMPK) activator. This study tested its potential cytoprotective effect in hydrogen peroxide (H2O2)-treated osteoblasts. In cultured MC3T3-E1 osteoblastic cells and primary murine osteoblasts, GSK621 significantly attenuated H2O2-induced cell death and apoptosis. AMPK activation was required for GSK621-induced osteoblast cytoprotection. Inhibition of AMPK, by AMPKalpha1 T172A mutation or shRNA silence, almost completely blocked GSK621-induced osteoblast cytoprotection. Reversely, introduction of a constitutively-active AMPKalpha1 (T172D) alleviated H2O2 injuries in MC3T3-E1 cells. Further, GSK621 increased nicotinamide adenine dinucleotide phosphate (NADPH) content in osteoblasts to inhibit H2O2-induced reactive oxygen species (ROS) production. Meanwhile, GSK621 activated cytoprotective autophagy in the osteoblasts. On the other hand, pharmacological inhibition of autophagy alleviated GSK621-mediated osteoblast cytoprotection against H2O2. These results suggest that targeted activation of AMPK by GSK621 ameliorates H2O2-induced osteoblast cell injuries.