title: Protein kinase Cdelta-dependent and -independent signaling in genotoxic response to treatment of desferroxamine, a hypoxia-mimetic agent.
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 PKCdelta 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 PKCdelta by RNAi (sh-PKCdelta) or expression of the kinase-dead (Lys376Arg) mutant of PKCdelta (PKCdeltaKD) conferred modulation on the cellular adaptive responses to DFO treatment. Notably, the time-dependent accumulation of DFO-induced phosphorylation of Ser-139-H2AX (gamma-H2AX), a hallmark for DNA damage, was altered by sh-PKCdelta, and sh-PKCdelta completely abrogated the activation of caspase-3 in DFO-treated cells. Expression of Lys376Arg-mutated PKCdelta-enhanced green fluorescent protein (EGFP) appears to abrogate DFO/hypoxia-induced activation of endogenous PKCdelta and caspase-3, suggesting that PKCdeltaKD-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 PKCdelta-dependent and -independent manners. In summary, these findings suggest that the activation of a PKCdelta-mediated signaling network is one of the critical contributing factors involved in fine-tuning of the DNA damage response to DFO treatment.
authors.affiliation: Department of Molecular Pharmacology, University of Southern California, Los Angeles, USA.
authors.forename: Carlos
authors.initials: C
authors.lastname: Clavijo
authors.forename: Jo-Lin
authors.initials: JL
authors.lastname: Chen
authors.forename: Kwang-Jin
authors.initials: KJ
authors.lastname: Kim
authors.forename: Mary E
authors.initials: ME
authors.lastname: Reyland
authors.forename: David K
authors.initials: DK
authors.lastname: Ann
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D004249:DNA Damage; D003676:Deferoxamine / Q000494:pharmacology*; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000860:Hypoxia; D051058:Oncogene Protein v-akt / Q000378:metabolism; D051745:Protein Kinase C-delta / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction
chemical_list: D051058:Oncogene Protein v-akt; D051745:Protein Kinase C-delta; D053148:Caspase 3; D003676:Deferoxamine