Protein kinase Cα/β inhibitor Go6976 promotes PC12 cell adhesion and spreading through membrane recruitment and activation of protein kinase Cδ

Go6976 is a nonglycosidic indolocarbazole compound widely used as a specific inhibitor of PKC alpha/beta. In experiments probing for a role of PKC alpha in human laminin-2-integrin-mediated cell adhesion and spreading of PC12 cells, we observed unexpected enhancements of adhesion, spreading and stress fiber formation to 1 mu M Go6976 with concomitant increase in membrane translocation of PKC delta and autophosphorylation of focal adhesion kinase (FAK). Importantly, enhanced cellular behavior and membrane translocation of PKCS induced by Go6976 was retained in siRNA-transfected PC12 cells to knockdown PKCa expression. Go6976 also induced laminin-dependent cell adhesion in NIH/3T3 and CV-1 fibroblasts, suggesting of a mechanism that may be common to multiple cell-types. A specific inhibitor of PKC delta, rottlerin, completely abrogated Go6976-dependent increase in PC12 cell adhesion to laminin as well as the activation of small GTPases, Rac1 and Cdc42, that are downstream of PKC delta in adhesion receptor signaling. siRNA knockdown of Rac1 and Cdc42 expression inhibited cell spreading and lamellipodia formation in PC12 cells. Overall, these results suggest that Go56976 may stimulate membrane recruitment of PKC delta through a mechanism that is independent of PKC alpha/beta signaling. In addition, the activation of Rac1 and Cdc42 by human laminin-2-integrin-dependent activation of PKG delta/FAK signaling mediates cell spreading and lamellipodia formation in PC12 cells. (c) 2012 Elsevier Inc. All rights reserved.