GSK2334470

GSK2334470 is a highly specific inhibitor of 3-phosphoinositide-dependent protein kinase 1(PDK1) with IC50 value of ~10nM [1].

GSK2334470 prevents PDK1 from activating full-length Akt1or mutant Akt1 lacking the PH domain. It also inhibits phosphorylation of the PDKtide peptide substrate. GSK2334470 shows no significant inhibitory effect on 93 other protein kinases (including 13 AGC-kinases) and 15 lipid kinases. GSK2334470 markedly inhibits the IGF1-induced T-loop phosphorylation of SGK1, SGK2 and SGK3 overexpressed in HEK293 cells. GSK2334470 is also reported to suppress the activity of S6K1. It inhibits the phosphorylation of both hydrophobic motif and T-loop of S6K1. To Akt1, GSK2334470 exerts same effects on the phosphorylation of T-loop but has no significant inhibition of hydrophobic motif phosphorylation. In PDK1K465E/K465E knock-in ES cells, GSK2334470 is more potent to inhibit Akt activation than in PDK1+/+ ES cells. Moreover, the inhibition of Akt activation shows to recede in U87 glioblastoma cells lack PTEN expression [1].

References:
[1] Najafov A, Sommer E, Axten J, et al. Characterization of GSK2334470, a novel and highly specific inhibitor of PDK1. Biochem. J, 2011, 433: 357-369.

Characterization of GSK2334470, a novel and highly specific inhibitor of PDK1.[Pubmed:21087210]

Biochem J. 2011 Jan 15;433(2):357-69.

PDK1 (3-phosphoinositide-dependent protein kinase 1) activates a group of protein kinases belonging to the AGC [PKA (protein kinase A)/PKG (protein kinase G)/PKC (protein kinase C)]-kinase family that play important roles in mediating diverse biological processes. Many cancer-driving mutations induce activation of PDK1 targets including Akt, S6K (p70 ribosomal S6 kinase) and SGK (serum- and glucocorticoid-induced protein kinase). In the present paper, we describe the small molecule GSK2334470, which inhibits PDK1 with an IC(5)(0) of ~10 nM, but does not suppress the activity of 93 other protein kinases including 13 AGC-kinases most related to PDK1 at 500-fold higher concentrations. Addition of GSK2334470 to HEK (human embryonic kidney)-293, U87 or MEF (mouse embryonic fibroblast) cells ablated T-loop residue phosphorylation and activation of SGK isoforms and S6K1 induced by serum or IGF1 (insulin-like growth factor 1). GSK2334470 also inhibited T-loop phosphorylation and activation of Akt, but was more efficient at inhibiting Akt in response to stimuli such as serum that activated the PI3K (phosphoinositide 3-kinase) pathway weakly. GSK2334470 inhibited activation of an Akt1 mutant lacking the PH domain (pleckstrin homology domain) more potently than full-length Akt1, suggesting that GSK2334470 is more effective at inhibiting PDK1 substrates that are activated in the cytosol rather than at the plasma membrane. Consistent with this, GSK2334470 inhibited Akt activation in knock-in embryonic stem cells expressing a mutant of PDK1 that is unable to interact with phosphoinositides more potently than in wild-type cells. GSK2334470 also suppressed T-loop phosphorylation and activation of RSK2 (p90 ribosomal S6 kinase 2), another PDK1 target activated by the ERK (extracellular-signal-regulated kinase) pathway. However, prolonged treatment of cells with inhibitor was required to observe inhibition of RSK2, indicating that PDK1 substrates possess distinct T-loop dephosphorylation kinetics. Our data define how PDK1 inhibitors affect AGC signalling pathways and suggest that GSK2334470 will be a useful tool for delineating the roles of PDK1 in biological processes.

Genetic inactivation or pharmacological inhibition of Pdk1 delays development and inhibits metastasis of Braf(V600E)::Pten(-/-) melanoma.[Pubmed:24037523]

Oncogene. 2014 Aug 21;33(34):4330-9.

Phosphoinositide-dependent kinase-1 (PDK1) is a serine/threonine protein kinase that phosphorylates members of the conserved AGC kinase superfamily, including AKT and protein kinase C (PKC), and is implicated in important cellular processes including survival, metabolism and tumorigenesis. In large cohorts of nevi and melanoma samples, PDK1 expression was significantly higher in primary melanoma, compared with nevi, and was further increased in metastatic melanoma. PDK1 expression suffices for its activity, owing to auto-activation, or elevated phosphorylation by phosphoinositide 3'-OH-kinase (PI3K). Selective inactivation of Pdk1 in the melanocytes of Braf(V600E)::Pten(-/-) or Braf(V600E)::Cdkn2a(-/-)::Pten(-/-) mice delayed the development of pigmented lesions and melanoma induced by systemic or local administration of 4-hydroxytamoxifen. Melanoma invasion and metastasis were significantly reduced or completely prevented by Pdk1 deletion. Administration of the PDK1 inhibitor GSK2334470 (PDKi) effectively delayed melanomagenesis and metastasis in Braf(V600E)::Pten(-/-) mice. Pdk1(-/-) melanomas exhibit a marked decrease in the activity of AKT, P70S6K and PKC. Notably, PDKi was as effective in inhibiting AGC kinases and colony forming efficiency of melanoma with Pten wild-type (WT) genotypes. Gene expression analyses identified Pdk1-dependent changes in FOXO3a-regulated genes, and inhibition of FOXO3a restored proliferation and colony formation of Pdk1(-/-) melanoma cells. Our studies provide direct genetic evidence for the importance of PDK1, in part through FOXO3a-dependent pathway, in melanoma development and progression.