MOLECULAR-CLONING OF A RETINA-SPECIFIC MEMBRANE GUANYLYL CYCLASE

We have isolated and characterized cDNA clones encoding the human retinal guanylyl cyclase (retGC), a novel member of the membrane guanylyl cyclase gene family. Like other membrane guanylyl cyclases,the 1101 aa retGC is predicted to have a hydrophobic amino-terminal signal sequence followed by a large extracellular domain, a single membrane spanning domain, a kinase homology domain, and a guanylyl cyclase catalytic domain. In contrast to other membrane guanylyl cyclases, such as natriuretic peptide receptors, retGC has a relatively high basal level of activity when expressed in human 293 cells. cGMP production by retGC is unaffected by any of the known natriuretic peptides. In situ hybridization analysis of a variety of rhesus monkey tissues showed retGC transcripts to be localized exclusively along the retinal outer nuclear layer, corresponding to the nuclei of the rod and cone photoreceptor cells. Our results suggest that retGC may synthesize cGMP required for recovery of the dark state after phototransduction.