Association of soluble guanylate cyclase with the sarcolemma of mammalian skeletal muscle fibers

Previous investigations have shown that NO-producing nitric oxide synthase (NOS)-1 and GO-generating heme oxygenase (HO-2) are associated with the sar colemma of skeletal muscle fibers in many mammalian species. Despite numero us roles ascribed to NO and possibly also CO in skeletal muscle, a specific receptor for both gases has hitherto not been found in myofibers. Therefor e, in the present work the appearance of the alpha1, beta1 and beta2 subuni ts of soluble guanylate cyclase (sGC), the most commonly known receptor for NO and potentially also CO, was analysed in mammalian skeletal muscles usi ng immunoblotting and immunohistochemistry. Immunoblotting with an antibody against the pi subunit of sGC revealed a band of 70 kDa corresponding to t he molecular weight of this protein. Immunohistochemistry with antibodies a gainst the alpha1, beta1 and beta2 sGC subunits showed that the larger part of positivity was present in the sarcolemma region of skeletal muscle fibe rs and colocalized with NOS-1 mainly in type II myofibers and with HO-2 in type I and type II myofibers. For the first time, sarcolemmal association o f sGC and its colocalization with NOS-1 generating the sGC-activator NO and with HO-2 producing the potential sGC upregulator CO have been demonstrate d in the present study. These results enable a better understanding of the role of NO and CO in myofibers and suggest a so far unknown molecular mecha nism for the interaction of sGC with the sarcolemma.