Activation of brain calcineurin (Cn) by Cu-Zn superoxide dismutase (SOD1) depends on direct SOD1-Cn protein interactions occurring in vitro and in vivo.
Cn (calcineurin) activity is stabilized by SOD1 (Cu-Zn superoxide dismutase), a phenomenon attributed to protection from superoxide (O2*-). The effects of O2*- on Cn are still controversial. We found that O2*-, generated either in vitro or in vivo did not affect Cn activity. Yet native bovine, recombinant human or rat, and two chimaeras of human SOD1-rat SOD1, all activated Cn, but SOD2 (Mn-superoxide dismutase) did not affect Cn activity. There was also a poor correlation between SOD1 dismutase activity and Cn activation. A chimaera of human N-terminal SOD1 and rat C-terminal SOD1 had little detectable dismutase activity, yet stimulated Cn activity the same as full-length human or rat SOD1. Nevertheless, there was evidence that the active site of SOD1 was involved in Cn activation based on the loss of activation following chelation of Cu from the active site of SOD1. Also, SOD1 engaged in the catalysis of O2*- dismutation was ineffective in activating Cn. SOD1 activation of Cn resulted from a 90-fold decrease in phosphatase K(m) without a change in V(max). A possible mechanism for the activation of Cn was identified in our studies as the prevention of Fe and Zn losses from the active site of Cn, suggesting a conformation-dependent SOD1-Cn interaction. In neurons, SOD1 and Cn were co-localized in cytoplasm and membranes, and SOD1 co-immunoprecipitated with Cn from homogenates of brain hippocampus and was present in immunoprecipitates as large multimers. Pre-incubation of pure SOD1 with Cn caused SOD1 multimer formation, an indication of an altered conformational state in SOD1 upon interaction with Cn.
Agbas
Abdulbaki
A
Department of Pharmacology and Toxicology and Center for Neurobiology and Immunology Research, University of Kansas, Lawrence, KS 66045, USA.
Hui
Dongwei
D
Wang
Xinsheng
X
Tek
Vekalet
V
Zaidi
Asma
A
Michaelis
Elias K
EK
D000818:Animals; D001921:Brain / Q000378:metabolism*; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D002614:Chelating Agents / Q000378:metabolism; D002863:Chromogenic Compounds / Q000378:metabolism; D004789:Enzyme Activation; D006540:Herbicides / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008297:Male; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism; D010269:Paraquat; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D011994:Recombinant Proteins; D012118:Resorcinols / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D000072105:Superoxide Dismutase-1; D015032:Zinc / Q000378:metabolism
D002614:Chelating Agents; D002863:Chromogenic Compounds; D006540:Herbicides; D016877:Oxidants; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D012118:Resorcinols; C000606290:SOD1 protein, human; D006861:Hydrogen Peroxide; D002374:Catalase; C000606292:Sod1 protein, rat; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D019703:Calcineurin; D015032:Zinc; C028398:4-(2-pyridylazo)resorcinol; D010269:Paraquat