Inhibition of PKCalpha induces a PKCdelta-dependent apoptotic program in salivary epithelial cells.
We have used expression of a kinase dead mutant of PKCalpha (PKCalphaKD) to explore the role of this isoform in salivary epithelial cell apoptosis. Expression of PKCalphaKD 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 PKCdelta and PKCzeta, 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 PKCdelta activity is essential for the apoptotic response of salivary epithelial cells to a variety of cell toxins. To explore the contribution of PKCdelta to PKCalphaKD-induced apoptosis, salivary epithelial cells were cotransduced with PKCalphaKD and PKCdeltaKD expression vectors. Inhibition of endogenous PKCdelta blocked the ability of PKCalphaKD to induce apoptosis as indicated by cell morphology, DNA fragmentation, and caspase-3 activation, indicating that PKCdelta activity is required for the apoptotic program induced under conditions where PKCalpha is inhibited. These findings indicate that PKCalpha functions as a survival factor in salivary epithelial cells, while PKCdelta functions to regulate entry into the apoptotic pathway.
Matassa
A A
AA
Department of Craniofacial Biology, School of Dentistry, University of Colorado Health Sciences Center, Denver 80262, USA.
Kalkofen
R L
RL
Carpenter
L
L
Biden
T J
TJ
Reyland
M E
ME
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002469:Cell Separation; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism*; D005434:Flow Cytometry; D016193:G1 Phase; D005982:Glutathione Transferase / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010306:Parotid Gland / Q000166:cytology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D051381:Rats; D012469:Salivary Glands / Q000378:metabolism*; D013997:Time Factors
D004791:Enzyme Inhibitors; D004247:DNA; D005982:Glutathione Transferase; C497260:Prkcd protein, rat; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases