COMMUNICATION - INTERACTION OF NEURONAL NITRIC-OXIDE SYNTHASE WITH CAVEOLIN-3 IN SKELETAL-MUSCLE - IDENTIFICATION OF A NOVEL CAVEOLIN SCAFFOLDING INHIBITORY DOMAIN/

Neuronal nitric-oxide synthase (nNOS) has been shown previously to int eract with alpha(1)-syntrophin in the dystrophin complex of skeletal m uscle. In the present study, we have examined whether nNOS also intera cts with caveolin-3 in skeletal muscle. nNOS and caveolin-3 are coimmu noprecipitated from rat skeletal muscle homogenates by antibodies dire cted against either of the two proteins. Synthetic peptides correspond ing to the membrane-proximal caveolin-3 residues 65-84 and 109-130 and homologous caveolin-1 residues 82-101 and 135-156 potently inhibit th e catalytic activity of purified, recombinant nNOS. Purified nNOS also binds to a glutathione S-transferase-caveolin-1 fusion protein in in vitro binding assays. In vitro binding is completely abolished by prei ncubation of nNOS with either of the two caveolin-3 inhibitory peptide s. Interactions between nNOS and caveolin-3, therefore, appear to be d irect and to involve two distinct caveolin scaffolding/inhibitory doma ins. Other caveolin-interacting enzymes, including endothelial nitric- oxide synthase and the c-Src tyrosine kinase, are also potently inhibi ted by each of the four caveolin peptides. Inhibitory interactions med iated by two different caveolin domains may thus be a general feature of enzyme docking to caveolin proteins in plasmalemmal caveolae.