title: 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.
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Victoria, Australia.
authors.forename: Rong
authors.initials: R
authors.lastname: Li
authors.forename: Juliana
authors.initials: J
authors.lastname: Soosairajah
authors.forename: Daniel
authors.initials: D
authors.lastname: Harari
authors.forename: Ami
authors.initials: A
authors.lastname: Citri
authors.forename: John
authors.initials: J
authors.lastname: Price
authors.forename: Hooi Ling
authors.initials: HL
authors.lastname: Ng
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Morton
authors.forename: Michael W
authors.initials: MW
authors.lastname: Parker
authors.forename: Yosef
authors.initials: Y
authors.lastname: Yarden
authors.forename: Ora
authors.initials: O
authors.lastname: Bernard
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D020134:Catalytic Domain; D019281:Dimerization; D004789:Enzyme Activation; D004795:Enzyme Stability; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006207:Half-Life; D054461:Lim Kinases; D010766:Phosphorylation; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D018841:HSP90 Heat-Shock Proteins; D011494:Protein Kinases; D054461:Lim Kinases