Proteolytic activation of protein kinase C-epsilon by caspase-mediated processing and transduction of antiapoptotic signals.
Several novel protein kinase C (PKC) isozymes have been identified as substrates for caspase-3. We have previously shown that novel PKCepsilon is cleaved during apoptosis in MCF-7 cells that lack any functional caspase-3. In the present study, we show that in vitro-translated PKCepsilon is processed by human recombinant caspase-3, -7, and -9. Tumor necrosis factor-alpha (TNF) triggered processing of PKCepsilon to a 43-kDa carboxyl-terminal fragment, and cell-permeable caspase inhibitors prevented TNF-induced processing of PKCepsilon in MCF-7 cells. PKCepsilon was cleaved primarily at the SSPD downward arrow G site to generate two fragments with an approximate molecular mass of 43 kDa. It was also cleaved at the DDVD downward arrow C site to generate two fragments with molecular masses of 52 and 35 kDa. Treatment of MCF-7 cells with TNF resulted in the activation of PKCepsilon, and mutation at the SSPD downward arrow G (D383A) site inhibited proteolytic activation of PKCepsilon. Overexpression of wild-type but not dominant-negative PKCepsilon in MCF-7 cells delayed TNF-induced apoptosis, and mutation at the D383A site prevented antiapoptotic activity of PKCepsilon. These results suggest that cleavage of PKCepsilon by caspase-7 at the SSPD downward arrow G site results in the activation of PKCepsilon. Furthermore, activation of PKCepsilon was associated with its antiapoptotic function.
Basu
Alakananda
A
Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth 76107, USA. abasu@hsc.unt.edu
Lu
Dongmei
D
Sun
Baohua
B
Moor
Andrea N
AN
Akkaraju
Giridhar Rao
GR
Huang
Jie
J
D017209:Apoptosis; D053179:Caspase 7; D020169:Caspases / Q000502:physiology*; D004789:Enzyme Activation; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008970:Molecular Weight; D010446:Peptide Fragments / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D007527:Isoenzymes; D010446:Peptide Fragments; D014409:Tumor Necrosis Factor-alpha; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; C505520:CASP7 protein, human; D053179:Caspase 7; D020169:Caspases