RECEPTORS AND SIGNAL TRANSDUCTION |
Protein kinase C
-dependent and -independent signaling in genotoxic response to treatment of desferroxamine, a hypoxia-mimetic agent
Carlos Clavijo,1,6
Jo-Lin Chen,1,4
Kwang-Jin Kim,1,2,3
Mary E. Reyland,5 , and
David K. Ann1,2,4
Departments of 1Molecular Pharmacology and Toxicology and 2Medicine, the 3Will Rogers Institute Pulmonary Research Center, University of Southern California, Los Angeles; and 4Department of Clinical and Molecular Pharmacology, City of Hope National Medical Center, Duarte, California; 5Department of Craniofacial Biology/Cell and Developmental Biology, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado; and 6Department of Biology, Universidad Nacional de Colombia, Bogota, Colombia
Received for publication 8 August 2006.
Accepted for publication 15 February 2007.
Abstract:
Protein kinase C (PKC) plays a critical role in diseases such as cancer, stroke, and cardiac ischemia and participates in a variety of signal transduction pathways including apoptosis, cell proliferation, and tumor suppression. Here, we demonstrate that PKC
is proteolytically cleaved and translocated to the nucleus in a time-dependent manner on treatment of desferroxamine (DFO), a hypoxia-mimetic agent. Specific knockdown of the endogenous PKC by RNAi (sh-PKC) or expression of the kinase-dead (Lys376Arg) mutant of PKC (PKCKD) conferred modulation on the cellular adaptive responses to DFO treatment. Notably, the time-dependent accumulation of DFO-induced phosphorylation of Ser-139-H2AX (
-H2AX), a hallmark for DNA damage, was altered by sh-PKC, and sh-PKC completely abrogated the activation of caspase-3 in DFO-treated cells. Expression of Lys376Arg-mutated PKC-enhanced green fluorescent protein (EGFP) appears to abrogate DFO/hypoxia-induced activation of endogenous PKC and caspase-3, suggesting that PKCKD-EGFP serves a dominant-negative function. Additionally, DFO treatment also led to the activation of Chk1, p53, and Akt, where DFO-induced activation of p53, Chk1, and Akt occurred in both PKC-dependent and -independent manners. In summary, these findings suggest that the activation of a PKC-mediated signaling network is one of the critical contributing factors involved in fine-tuning of the DNA damage response to DFO treatment.
Key Words: DNA damage • caspase-3 • Akt
Address for reprint requests and other correspondence: D. K. Ann, City of Hope National Medical Center, KCRB Rm. 1004, 1500 E. Duarte Road, Duarte, CA 91010 (e-mail: dann{at}coh.org)
