Induction of apoptosis by protein kinase C delta is independent of its kinase activity.
Protein kinase C, a multigene family of phospholipid-dependent and diacylglycerol-activated Ser/Thr protein kinases, is a key component in many signal transduction pathways. The kinase activity was thought to be essential for a plethora of biological processes attributed to these enzymes. Here we show that at least one protein kinase C function, the induction of apoptosis by protein kinase C delta, is independent of the kinase activity. Stimulation of green fluorescent protein-protein kinase C delta fusion protein with phorbol ester or diacylglycerol led to its redistribution within seconds after the stimulus. Membrane blebbing, an early hallmark of apoptosis, was visible as early as 20 min after stimulation, and nuclear condensation was visible after 3-5 h. Apoptosis could be inhibited by expression of Bcl-2 but not by specific protein kinase C inhibitors. In addition, a kinase-negative mutant of protein kinase C delta also induced apoptosis to the same extent as the wild type enzyme. Apoptosis was confined to the protein kinase C delta-overexpressing cells. Stimulation of overexpressed protein kinase C epsilon did not result in increased apoptosis. Our results indicate that distinct protein kinase C isozymes induce apoptosis in vascular smooth muscle cells. More importantly, they show that some protein kinase C effector functions are independent of the catalytic activity.
Goerke
Axel
A
Medical School Hanover, Department of Nephrology, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
Sakai
Norio
N
Gutjahr
Elisabeth
E
Schlapkohl
Walter A
WA
Mushinski
J Frederic
JF
Haller
Hermann
H
Kolch
Walter
W
Saito
Naoaki
N
Mischak
Harald
H
D000818:Animals; D017302:Annexins / Q000032:analysis; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D002843:Chromatin / Q000502:physiology; D049452:Green Fluorescent Proteins; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics; D008928:Mitochondria / Q000201:enzymology; D011493:Protein Kinase C / Q000378:metabolism*; D064546:Protein Kinase C beta; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection
D017302:Annexins; D002843:Chromatin; D007527:Isoenzymes; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon