title: Protein kinase C delta is essential for etoposide-induced apoptosis in salivary gland acinar cells.
abstract: We have previously shown that parotid C5 salivary acinar cells undergo apoptosis in response to etoposide treatment as indicated by alterations in cell morphology, caspase-3 activation, DNA fragmentation, sustained activation of c-Jun N-terminal kinase, and inactivation of extracellular regulated kinases 1 and 2. Here we report that apoptosis results in the caspase-dependent cleavage of protein kinase C-delta (PKCdelta) to a 40-kDa fragment, the appearance of which correlates with a 9-fold increase in PKCdelta activity. To understand the function of activated PKCdelta in apoptosis, we have used the PKCdelta-specific inhibitor, rottlerin. Pretreatment of parotid C5 cells with rottlerin prior to the addition of etoposide blocks the appearance of the apoptotic morphology, the sustained activation of c-Jun N-terminal kinase, and inactivation of extracellular regulated kinases 1 and 2. Inhibition of PKCdelta also partially inhibits caspase-3 activation and DNA fragmentation. Immunoblot analysis shows that the PKCdelta cleavage product does not accumulate in parotid C5 cells treated with rottlerin and etoposide together, suggesting that the catalytic activity of PKCdelta may be required for cleavage. PKCalpha and PKCbeta1 activities also increase during etoposide-induced apoptosis. Inhibition of these two isoforms with Gö6976 slightly suppresses the apoptotic morphology, caspase-3 activation, and DNA fragmentation, but has no effect on the sustained activation of c-Jun N-terminal kinase or inactivation of extracellular regulated kinase 1 and 2. These data demonstrate that activation of PKCdelta is an integral and essential part of the apoptotic program in parotid C5 cells and that specific activated isoforms of PKC may have distinct functions in cell death.
authors.affiliation: Department of Basic Science and Oral Research, School of Dentistry, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. mary.reyland@UCHSC.edu
authors.forename: M E
authors.initials: ME
authors.lastname: Reyland
authors.forename: S M
authors.initials: SM
authors.lastname: Anderson
authors.forename: A A
authors.initials: AA
authors.lastname: Matassa
authors.forename: K A
authors.initials: KA
authors.lastname: Barzen
authors.forename: D O
authors.initials: DO
authors.lastname: Quissell
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001578:Benzopyrans / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D053938:DNA Fragmentation; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D064546:Protein Kinase C beta; D051745:Protein Kinase C-delta; D012469:Salivary Glands / Q000187:drug effects / Q000201:enzymology*
chemical_list: D000098:Acetophenones; D000972:Antineoplastic Agents, Phytogenic; D001578:Benzopyrans; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D005047:Etoposide; C085746:rottlerin; C497258:PRKCD protein, human; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051745:Protein Kinase C-delta; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases