TY - JOUR T1 - Protein Kinase Cδ Is a Key Downstream Mediator of Manganese-Induced Apoptosis in Dopaminergic Neuronal Cells JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 46 LP - 55 DO - 10.1124/jpet.104.078469 VL - 313 IS - 1 AU - Calivarathan Latchoumycandane AU - Vellareddy Anantharam AU - Masashi Kitazawa AU - Yongjie Yang AU - Arthi Kanthasamy AU - Anumantha G. Kanthasamy Y1 - 2005/04/01 UR - http://jpet.aspetjournals.org/content/313/1/46.abstract N2 - Manganese (Mn) exposure causes manganism, a neurological disorder similar to Parkinson's disease. However, the cellular mechanism by which Mn induces dopaminergic neuronal cell death remains unclear. In the present study, we sought to investigate the key downstream apoptotic cell signaling events that contribute to Mn-induced cell death in mesencephalic dopaminergic neuronal (N27) cells. Mn exposure induced a dose-dependent increase in neuronal cell death in N27 cells. The cell death was accompanied by sequential activation of mitochondrial-dependent proapoptotic events, including cytochrome c release, caspase-3 activation, and DNA fragmentation, but not caspase-8 activation, indicating that the mitochondrial-dependent apoptotic cascade primarily triggers Mn-induced apoptosis. Notably, Mn treatment proteolytically activated protein kinase Cδ (PKCδ), a member of a novel class of protein kinase C. The caspase-3 specific inhibitor benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethylketone (Z-DEVD-FMK) significantly blocked PKCδ cleavage and its kinase activity, indicating that caspase-3 mediates the proteolytic activation. Cotreatment with the PKCδ inhibitor rottlerin or the caspase-3 inhibitor Z-DEVD-FMK almost completely blocked Mn-induced DNA fragmentation. Additionally, N27 cells expressing a catalytically inactive PKCδK376R protein (PKCδ dominant negative mutant) or a caspase cleavage resistant PKCδD327A protein (PKCδ cleavage resistant mutant) were found to be resistant to Mn-induced apoptosis. To further establish the proapoptotic role of PKCδ, RNA interference-mediated gene knockdown was performed. Small interfering RNA suppression of PKCδ expression protected N27 cells from Mn-induced apoptotic cell death. Collectively, these results suggest that caspase-3-dependent proteolytic activation of PKCδ plays a key role in Mn-induced apoptotic cell death. The American Society for Pharmacology and Experimental Therapeutics ER -