Calcium/calmodulin-dependent protein kinase I inhibits neuronal nitric-oxide synthase activity through serine 741 phosphorylation

We demonstrate here that neuronal nitric-oxide synthase (nNOS) is phosphorylated and inhibited by a constitutively active form of Ca2+/calmodulin (CaM)-dependent protein kinase I (CaM-K 11-293). Substitution of Ser(741) to Ala in nNOS blocked the phosphorylation and the inhibitory effect. Mimicking phosphorylation at Ser(741) by Ser to Asp mutation resulted in decreased binding of and activation by CaM, since the mutation was within the CaM-binding domain. CaM-K 11-293 gave phosphorylation of nNOS at Ser(741) in transfected cells, resulting in 66-70% inhibition of nNOS activity. Wild-type CaM-K I also did phosphorylate nNOS at Ser(741) in transfected cells, but either CaM-K II or CaM-K IV did not. These results raise the possibility of a novel cross-talk between nNOS and CaM-K I through the phosphorylation of Ser(741) on nNOS. (C) 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.