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

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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.