1. ¹Departments of Craniofacial Biology, School of Dentistry, University of Colorado Health Sciences Center, Denver, CO 80262, USA
2. ²Cell and Structural Biology, School of Medicine, University of Colorado Health Sciences Center, Denver, CO 80262, USA
3. ³Garvan Institute of Medical Research, Sydney, Australia

Correspondence: ME Reyland, Department of Craniofacial Biology, University of Colorado Health Sciences Center, 4200 East Ninth Avenue, Box C286, Denver, CO 80262, USA. Tel: +1 303 315 3236; Fax: +1 303 315 3013; E-mail: mary.reyland@uchsc.edu

Received 28 August 2001; Revised 25 July 2002; Accepted 12 September 2002.

Abstract

We have used expression of a kinase dead mutant of PKC (PKCKD) to explore the role of this isoform in salivary epithelial cell apoptosis. Expression of PKCKD by adenovirus-mediated transduction results in a dose-dependent induction of apoptosis in salivary epithelial cells as measured by the accumulation of sub-G1 DNA, activation of caspase-3, and cleavage of PKC and PKC, known caspase substrates. Induction of apoptosis is accompanied by nine-fold activation of c-Jun-N-terminal kinase, and an approximately two to three-fold increase in activated mitogen-activated protein kinase (MAPK) as well as total MAPK protein. Previous studies from our laboratory have shown that PKC activity is essential for the apoptotic response of salivary epithelial cells to a variety of cell toxins. To explore the contribution of PKC to PKCKD-induced apoptosis, salivary epithelial cells were cotransduced with PKCKD and PKCKD expression vectors. Inhibition of endogenous PKC blocked the ability of PKCKD to induce apoptosis as indicated by cell morphology, DNA fragmentation, and caspase-3 activation, indicating that PKC activity is required for the apoptotic program induced under conditions where PKC is inhibited. These findings indicate that PKC functions as a survival factor in salivary epithelial cells, while PKC functions to regulate entry into the apoptotic pathway.