Activation of protein kinase Cα signaling prevents cytotoxicity and mutagenicity following lead acetate in CL3 human lung cancer cells

Protein kinase C (PKC) family of serine/threonine protein kinases is sensitive signaling transducers in response to lead acetate (Pb) that could transmit phosphorylation cascade for proliferation and dedifferentiation of neural cells. However, little is known as to the impact of PKC on Pb genotoxicity. Here we investigate whether Pb activates the conventional/classical subfamily of PKC (cPKC) signaling to affect cytotoxicity and mutagenicity in CL3 human non-small-cell lung adenocarcinoma cells. Pb specifically promoted membrane localization of the alpha isoform of PKC in CL3 cells. Pb also elicited Raf-1 activation as measured by the induction of phospho-Raf-1(S338) and the dissociation from the Raf-1 kinase inhibitor protein. inhibition of cPKC activity using Go6976 or depletion of PKC alpha by introducing specific small interfering RNA blocked the induction of phospho-Raf-1(S338), phospho-MKK1/2 and phospho-ERK1/2 in cells exposed to Pb. Intriguingly, declining PKC alpha enhanced the Pb cytotoxicity and revealed the Pb mutagenicity at the hprt gene. The results suggest that PKC alpha is obligatory for activation of the Raf-1-MKK1/2-ERK1/2 signaling module and plays a defensive role against cytotoxicity and mutagenicity following Pb exposure. Results obtained in this study also support our previous report showing that ERK1/2 activity is involved in preventing Pb genotoxicity. (C) 2008 Elsevier Ireland Ltd. All rights reserved.