Discovery and Characterization of a Cell-Permeable, Small-Molecule c-Abl Kinase Activator that Binds to the Myristoyl Binding Site

Abstract

c-Abl kinase activity is regulated by a unique mechanism involving the formation of an autoinhibited conformation in which the N-terminal myristoyl group binds intramolecularly to the myristoyl binding site on the kinase domain and induces the bending of the αI helix that creates a docking surface for the SH2 domain. Here, we report a small-molecule c-Abl activator, DPH, that displays potent enzymatic and cellular activity in stimulating c-Abl activation. Structural analyses indicate that DPH binds to the myristoyl binding site and prevents the formation of the bent conformation of the αI helix through steric hindrance, a mode of action distinct from the previously identified allosteric c-Abl inhibitor, GNF-2, that also binds to the myristoyl binding site. DPH represents the first cell-permeable, small-molecule tool compound for c-Abl activation.

The Src kinases Hck, Fgr, and Lyn activate Abl2/Arg to facilitate IgG-mediated phagocytosis andLeishmaniainfection

“…The action of SFKs and Arg allows phosphorylation of their downstream mediator CrkII during FcR engagement by amastigotes. We also find that DPH increases CrkII phosphorylation in an Arg-dependent manner, consistent with previous observations (Yang et al, 2011). Clearly, SFKs and Arg-independent mechanisms also contribute to IgGmediated phagocytosis and amastigote uptake, given that inhibiting both kinases does not completely prevent these processes.…”

“…We find that activating Arg in Hck −/− Fgr −/− Lyn −/− BMDMs with low or sub-EC 50 doses (Yang et al, 2011) of DPH rescues uptake. Ours is the first demonstration that activating Abl family kinases facilitates phagocytosis.…”

“…To determine whether a SFK-Arg signaling pathway governed amastigote uptake, we first treated Hck −/− Fgr −/− Lyn −/− BMDMs with imatinib. The IC 50 of imatinib for Abl is 600 nM (Buchdunger et al, 1995) and its CC 50 is ≥20 μM for a 2-h incubation with RAW 264.7 cells; hence, 3.3 μM was selected as in Wetzel et al, 2012 We then used the small-molecule Abl family kinase activator DPH (Yang et al, 2011) to test whether activating Arg stimulated phagocytosis and amastigote uptake. DPH is known to activate Arg (Simpson et al, 2015) and Abl, with an EC 50 of 250-400 nM (Yang et al, 2011); its CC 50 is ≥10 μM for BMDMs.…”

Normal ABL1 is a tumor suppressor and therapeutic target in human and mouse leukemias expressing oncogenic ABL1 kinases

“…47 To determine whether DPH was able to induce and/or maintain the activity of ABL1 kinase under imatinib treatment, ABL1 was overexpressed in Phoenix cells followed by treatment with 10 mM DPH, 1 mM imatinib, or a combination of the 2 agents. DPH induced approximately eightfold and fourfold increase of phospho-Y245-ABL1, indicative of ABL1-kinase activation, in nuclear and cytoplasmic fractions, respectively ( Figure 7A).…”

Allosterische Kinaseinhibitoren

“…Neben den oben beschriebenen Myristattaschen-Inhibitoren wurde in einem Hochdruchsatz-Screen eine weitere Klasse von Molekülen beschrieben, welche die ABL-Myristattasche binden kön-nen [23]. Im Gegensatz zu GNF-2/5 und ABL001 konnten die Autoren interessanterweise zeigen, dass DPH eine starker Aktivator (und nicht Inhibitor) der Kinaseaktivität von c-ABL ist.…”