HSP27 modulates agonist-induced association of translocated RhoA and PKC-α in muscle cells of the colon

Abstract

The recruitment of signal transduction molecules to the membrane is crucial for the efficient coupling of extracellular signals and contractile response. The trafficking is dynamic. We have investigated a possible cross talk between agonist-induced association of translocated RhoA and translocated protein kinase C-α (PKC-α) and a role for heat shock protein 27 (HSP27) in mediating this interaction. Immunoprecipitation with HSP27 monoclonal antibody followed by immunoblotting with either RhoA antibody or PKC-α antibody indicated that acetylcholine induced associations of HSP27-RhoA and HSP27-PKC-α in the membrane fraction but not in the cytosolic fraction. Immunoprecipitation with anti-RhoA monoclonal antibody followed by immunoblotting with PKC-α antibody indicated that acetylcholine induced a significant complexing of RhoA-PKC-α in the membrane fraction but not in the cytosolic fraction. In summary, the data indicate that agonist-induced contraction is associated with 1) association of translocated RhoA with HSP27 on the membrane, 2) association of translocated PKC-α with HSP27 on the membrane, and 3) association of PKC-α with RhoA on the membrane. The data suggest an important role for HSP27 in modulating a multiprotein complex that includes translocated RhoA and PKC-α.