Hsp90 increases LIM kinase activity by promoting its homo‐dimerization

Abstract

LIM kinase 1 (LIMK1) is a serine protein kinase that regulates the actin cytoskeleton by phosphorylation and inactivation of actin depolymerizing factor cofilin. LIMK1 activity is regulated by the Rho-GTPases via their serine/threonine kinase effectors Rho-kinase and p21-activated kinases 1 and 4 that phosphorylate LIMK1 on threonine 508 in its activation loop. The purpose of this study was to elucidate the pathway leading to the stability of LIMK1, a protein with a half-life of approximately 20 h. Because the half-life of kinase-dead LIMK1 is only 4 h, it is suggestive that trans- or auto-phosphorylation is responsible for the stabilization of LIMK1. Using known Hsp90 inhibitors, we have shown that the half-life of LIMK1 in cells depends on the presence of active Hsp90. Furthermore, endogenous LIMK1 coimmunoprecipitated with endogenous Hsp90 and this interaction promoted LIMK1 homodimer formation as seen by cross-linking experiments. Hsp90 binds LIMK1 via a recognition sequence within the LIMK1 kinase domain, homologous to that of ErbB-2. Mutation of a proline residue within this sequence to glutamic acid reduces its interaction with Hsp90, inhibits homodimer formation, and reduces its half-life to 4 h. These findings implicate Hsp90 in the stabilization of LIMK1 by promoting homodimer formation and transphosphorylation.

Heat Shock Protein 90 Inhibitors Protect and Restore Pulmonary Endothelial Barrier Function

“…Protein Swo1, a fission yeast analog of hsp90, facilitates myosin II assembly (41). Conversely, inhibition of hsp90 attenuates or abolishes its effects on the actomyosin cytoskeleton (38)(39)(40)(41). In the present study, TGF-b1-induced hyperpermeability was associated with increased hsp27 phophorylation and hsp90-hsp27 complex formation; both of these effects were prevented by radicicol.…”

“…Interaction of hsp90 with N-WASP protects N-WASP from proteasome-dependent degradation, and by promoting v-Src-dependent N-WASP phosphorylation, amplifies N-WASP-dependent actin polymerization (39). Hsp90 also stabilizes/activates LIM kinase, promoting actin polymerization by inactivation of the actin depolymerizing factor, cofilin (40). Protein Swo1, a fission yeast analog of hsp90, facilitates myosin II assembly (41).…”

The HSP90 Inhibitor Ganetespib Synergizes with the MET Kinase Inhibitor Crizotinib in both Crizotinib-Sensitive and -Resistant MET-Driven Tumor Models

“…1A, endogenous HSP90 coprecipitated, albeit weakly, with wtMET. Previous reports by us and others have suggested that the activated states of some HSP90-dependent kinases have a greater dependence on HSP90 (31)(32)(33). To determine if this were the case for MET, we compared the degree of wtMET-HSP90 interaction in the presence and absence of the MET ligand HGF.…”

LIM Kinase 1 (LIMK1) Interacts with Tropomyosin-related Kinase B (TrkB) and Mediates Brain-derived Neurotrophic Factor (BDNF)-induced Axonal Elongation

“…The dimerization of receptors induces autophosphorylation in the kinase domain of the Trk receptors, followed by the activation of various signaling pathways (35). Coincidentally, the activity and stability of LIMK1 is also regulated by homo-dimerization (36). LIMK1 homo-dimerization could induce its transphosphorylation and thus increase LIMK1 activity.…”