A functional interaction between CPI-17 and RACK1 proteins in bronchial smooth muscle cells

CPI-17 is a phosphorylation-dependent inhibitor of smooth muscle myosin light chain. Using yeast two-hybrid system, we have identified the receptor for activated C kinase 1 (RACK1) as a novel interaction partner of CPI-17. The direct interaction and co-localization of CPI-17 with RACK1 were confirmed by immunoprecipitation and confocal microscopy analysis, respectively. An in vitro assay system using recombinant/purified proteins revealed that the PKC-mediated phosphorylation of CPI-17 was augmented in the presence of RACK1. These results suggest that RACK1 may play a role in PKC/CPI-17 signaling pathway.

Research highlights
► Yeast two-hybrid screening identified RACK1 as an interaction partner of CPI-17.
► The direct interaction of CPI-17 with RACK1 was confirmed by immunoprecipitation.
► CPI-17 and RACK1 were colocalized in cytosol of the cells.
► RACK1 facilitated the phosphorylation of CPI-17 mediated by PKC.
► Thus, RACK1 is one of the binding partners of CPI-17.