Molecular cloning of a regulatory protein for membrane-bound guanylate cyclase GC-A.

Activation of membrane-bound guanylate cyclase GC-A by atrial natriuretic factor (ANF) may require the involvement of accessory proteins. To identify these postulated proteins, we isolated a 1. 0-kb cDNA clone from a rat brain expression library using a polyclonal antiserum against mastoparan. The 1.0-kb cDNA encodes a protein of 111 amino acids. Expression of this cDNA in COS-7 cells potentiated ANF-stimulated GC-A activity. Therefore, the 1.0-kb gene encodes a guanylate cyclase regulatory protein (GCRP). Fluorescence microscopy studies using the fusion protein of GCRP with green fluorescence protein (GFP) indicated that GCRP was present in the cytosol in PC12 cells, but translocated toward the plasma membrane in the presence of ANF. Coimmunoprecipitation experiments indicate that GCRP associates with GC-A in the presence of ANF. These results suggest that ANF induces the association of GCRP with GC-A and this association contributes to the activation of GC-A.