Submitted on March 20, 2009
Revised on September 23, 2009
Accepted on October 13, 2009
Caspase-mediated Protein Kinase C-Delta cleavage is necessary for apoptosis of Vascular Smooth Muscle Cells
Kaori Kato1, Dai Yamanouchi1, Karla Esbona2, Kentaro Kamiya, Fan Zhang, K. Craig Kent, and Bo Liu2*
1 University of Wisconsin
2 University of Wisconsin Madison
* To whom correspondence should be addressed. E-mail: LIUB{at}surgery.wisc.edu.
Apoptotic death of vascular smooth muscle cells (SMCs) is a prominent feature of blood vessel remodeling and various vascular diseases. We have previously shown that Protein Kinase C-delta (PKC
) plays a critical role in SMC apoptosis. In this study, we tested the importance of PKC proteolytic cleavage and tyrosine phosphorylation within the apoptosis pathway. Using hydrogen peroxide as a paradigm for oxidative stress, we showed that proteolytic cleavage of PKC occurred in SMCs that underwent apoptosis while tyrosine phosphorylation was detected only in necrotic cells. Furthermore, using a peptide (z-DIPD-fmk) that mimics the caspase-3 binding motif within the linker region of PKC, we were able to prevent the cleavage of PKC as well as apoptosis. Inhibition of PKC with rottlerin or siRNA diminished caspase-3 cleavage, caspase-3 activity, cleavage of poly (ADP-ribose) polymerase (PARP), cleavage of PKC and DNA fragmentation, confirming the previously reported role of PKC in initiation of apoptosis. In contrast, z-DIPD-fmk markedly diminished caspase-activity, cleavage of PKC and DNA fragmentation without affecting cleavage of caspase-3 and PARP. Taken together, our data suggest that caspase-3-mediated PKC cleavage underlies SMC apoptosis induced by oxidative stress, and that PKC acts both upstream and downstream of caspase-3.
