Isolation, cloning, and characterization of a new mammalian coronin familymember, coronin(se), which is regulated within the protein kinase C signaling pathway

In order to understand the regulatory role of protein kinase C (PKC) in sec retory epithelia, it is necessary to identify and characterize specific dow nstream targets. We previously identified one such protein in studies of ga stric parietal cells. This protein was referred to as pp66 because it migra ted with an apparent molecular mass of 66 kDa on SDS-polyacrylamide gels. T he phosphorylation of pp66 is increased by the cholinergic agonist, carbach ol, and by the PKC activator, phorbol-12-myristate-13-acetate, in a calcium -independent manner. In this study, we have purified pp66 to homogeneity an d cloned the complete open reading frame. GenBank(Tm) searches revealed a 4 5% homology with the Dictyostelium actin-binding protein, coronin, and simi lar to 67% homology with the previously cloned human and bovine coronin-lik e homologue, p57. pp66 appears to be most highly expressed in the gastroint estinal mucosa and in kidney and lung. Confocal microscopic studies of an e nhanced green fluorescent protein fusion construct of pp66 in cultured pari etal cells and in Madin-Darby canine kidney cells indicate that pp66 prefer entially localizes in F-actin-rich regions. On the basis of our findings, w e propose that pp66 may play an important, PKC-dependent role in regulating membrane/cytoskeletal rearrangements in epithelial cells. We have tentativ ely named this protein coronin(se), because it appears to be highly express ed in secretory epithelia.