NITRIC-OXIDE-SYNTHASE-I (NOS-I) IS A COSTAMERIC ENZYME IN RAT SKELETAL-MUSCLE

Previously, we and others have reported association of nitric oxide (N O)generating nitric oxide synthase I (NOS I) with dystrophin in the su bsarcolemmal cytoskeleton of striated muscle fibers. Since this struct ure shows a costameric organization the detailed distribution of NOS I and other molecules inside and outside the subsarcolemmal cytoskeleto n was investigated. Using catalytic histochemistry and immunohistochem istry on rat skeletal muscle NOS I was colocalized in the costameres t ogether with dystrophin, beta-dystroglycan, alpha-, beta- and gamma-sa rcogrycan, beta 1-integrin, vinculin, paxillin and caveolin-3. Additio nally, only NOS appeared in uncharacterized subsarcolemmal wave-like s tructures. These data show 1) a growing family of proteins assembled i n the costameres including NOS I as described here for the first time, 2) expanded distribution patterns for NOS I, and 3) therefore, presum ably uneven NO concentrations within the skeletal muscle fibers which may have implications for NO function.