SUBUNITS OF SOLUBLE GUANYLYL CYCLASE IN RAT AND GUINEA-PIG SENSORY GANGLIA

Soluble guanylyl cyclase is a heterodimeric (alpha,beta) enzyme genera ting the second messenger, cGMP, upon activation by the gaseous messen ger, nitric oxide. The occurrence and distribution of alpha(1)-, alpha (2)-, beta(1)- and beta(2)-subunits were investigated in trigeminal an d dorsal root ganglia on the mRNA and the protein level. Reverse trans cription PCR analysis demonstrated mRNA coding for alpha(1)-, alpha(2) -, and beta(1)-subunits in guinea-pig trigeminal and dorsal root gangl ia. In agreement with these data, immunoreactivity to the alpha(1)-sub unit was found in satellite and Schwann cells, while alpha(2)-subunit immunoreactivity was localized to axons of large diameter. The distrib ution of the beta(1)-subunit could not be studied on the protein level since the antiserum was ineffective in immunohistochemistry. However, previous studies and the RT-PCR data argue in favour of alpha(1)/beta (1)- and alpha(2)/beta(1)-heterodimerization and colocalization. In bo th species, beta(2)-subunit immunoreactivity was confined to neuronal perikarya, primarily of large diameter. Although these results were ob tained with two different antibodies directed against different epitop es, the corresponding mRNA could not be detected by RT-PCR analysis. T he reason for this discrepancy remains unclear, at present, but could be explained by a variant beta(2)- or highly homologous as yet unident ified beta-subunit. This study demonstrates the presence of soluble gu anylyl cyclase in sensory ganglia with a differential, cell type-speci fic distribution of the individual subunits.