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.
Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth 76107, USA. abasu@hsc.unt.edu
Alakananda
A
Basu
Dongmei
D
Lu
Baohua
B
Sun
Andrea N
AN
Moor
Giridhar Rao
GR
Akkaraju
Jie
J
Huang
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