title: Activation of protein kinase C delta by proteolytic cleavage contributes to manganese-induced apoptosis in dopaminergic cells: protective role of Bcl-2.
abstract: Chronic inorganic manganese exposure causes selective toxicity to the nigrostriatal dopaminergic system, resulting in a Parkinsonian-like neurological condition known as Manganism. Apoptosis has been shown to occur in manganese-induced neurotoxicity; however, the down-stream cellular target of caspase-3 that contributes to DNA fragmentation is not established. Herein, we demonstrate that proteolytic activation of protein kinase Cdelta (PKCdelta) by caspase-3 plays a critical role in manganese-induced apoptotic cell death. Treatment of PC12 cells with manganese caused a sequential activation of mitochondrial-dependent pro-apoptotic events, including mitochondrial membrane depolarization, cytochrome c release, caspase-3 activation, and DNA fragmentation. Overexpression of Bcl-2 in PC12 cells remarkably attenuated each of these events, indicating that the mitochondrial-dependent apoptotic cascade contributes to manganese-induced apoptosis. Furthermore, PKCdelta was proteolytically cleaved by caspase-3, causing a persistent activation of the kinase. The manganese-induced proteolytic cleavage of PKCdelta was significantly blocked by Bcl-2-overexpression. Administration of active recombinant PKCdelta induced DNA fragmentation in PC12 cells, suggesting a pro-apoptotic role of PKCdelta. Furthermore, expression of catalytically inactive mutant PKCdelta(K376R) via a lentiviral gene delivery system effectively attenuated manganese-induced apoptosis. Together, these results suggest that the mitochondrial-dependent caspase cascade mediates apoptosis via proteolytic activation of PKCdelta in manganese-induced neurotoxicity.
authors.affiliation: Parkinson Disorders Research Laboratory, Department of Biomedical Sciences, Iowa State University, 2062 Vetmed, Ames, IA 50011-1250, USA.
authors.forename: Masashi
authors.initials: M
authors.lastname: Kitazawa
authors.forename: Vellareddy
authors.initials: V
authors.lastname: Anantharam
authors.forename: Yongjie
authors.initials: Y
authors.lastname: Yang
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hirata
authors.forename: Arthi
authors.initials: A
authors.lastname: Kanthasamy
authors.forename: Anumantha G
authors.initials: AG
authors.lastname: Kanthasamy
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D053938:DNA Fragmentation / Q000187:drug effects / Q000235:genetics; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000502:physiology; D005786:Gene Expression Regulation / Q000235:genetics*; D019254:Genes, bcl-2 / Q000502:physiology*; D008345:Manganese / Q000494:pharmacology*; D016716:PC12 Cells; D011493:Protein Kinase C / Q000378:metabolism*; D051745:Protein Kinase C-delta; D051381:Rats
chemical_list: D008345:Manganese; C497260:Prkcd protein, rat; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D004298:Dopamine