Guanylate cyclase involved in the production of the second messenger cGMP (PubMed:24284209). Acts as a receptor for the NPLP1-4 peptide and modulates the innate immune IMD pathway in response to salt stress by inducing nuclear translocation of NF-kappa-B protein Rel which leads to increased expression of the antimicrobial peptide diptericin (PubMed:21893139). Plays a role in Sema-1a-mediated axon repulsion which is required for the correct establishment of neuromuscular connectivity (PubMed:15282266, PubMed:24284209). Required in developing embryonic somatic muscle for correct patterning of ventral and lateral muscles and for localization of integrin beta-ps at developing dorsal muscle myotendinous junctions (PubMed:23213443). Required for invagination, migration and lumen shape of the embryonic salivary gland by regulating the localization of the integrin-binding protein rhea/Talin to the visceral mesoderm surrounding the gland and maintaining the laminin matrix (PubMed:23862019). Required in the developing wing to regulate extracellular matrix (ECM) organization by activating the cGMP-dependent protein kinase For which represses the activity of matrix metalloproteases such as Mmp2 and decreases ECM matrix reorganization (PubMed:26440503). GTP = 3',5'-cyclic GMP + diphosphate Interacts with the semaphorin 1A receptor PlexA; PlexA enhances Gyc76C catalytic activity. Interacts with the PDZ domain-containing protein kermit; kermit increases cell surface expression of Gyc76C. In the adult, widely distributed in the head and thorax with highest levels in the optic lobe and central brain and expression also detected in the retina (PubMed:7759483). Expressed at similar levels in adult head and body (PubMed:7759483). In females, highly expressed in oocytes with lower levels in the digestive tract (PubMed:7759483). In mid-embryogenesis, enriched in the circular visceral mesoderm that overlies the migrating salivary gland and in the fat body that underlies the gland but at background levels in the gland itself (PubMed:23213443). In late embryogenesis, detected in the mature salivary gland, in the somatic body wall muscles and the tendon cells to which the muscles attach, and in the constricting midgut (PubMed:23213443). Also expressed in migrating tracheal cells at mid-embryogenesis and in the developed trachea at the end of embryogenesis with enrichment in the apical domains (PubMed:23213443). Expressed in embryo, larva, pupa and adult (PubMed:7706258, PubMed:7759483). Expressed at very high levels in early cleavage stage embryos at 0-2 hours followed by lower expression at 2-6 and 6-10 hours of embryogenesis (PubMed:7706258). During later stages of embryogenesis at 10-14 and 14-18 hours, expressed again at high levels, particularly in muscle fibers (PubMed:7706258). Very low levels in larval and pupal stages (PubMed:7706258). The guanylate cyclase domain is required for Sema-1a-mediated axon repulsion. The protein kinase domain is predicted to be catalytically inactive. Abnormal patterning of the somatic body wall muscles with numerous ventral and lateral muscles that fail to extend or are missing and reduced levels of integrin beta-ps at dorsal muscle myotendinous junctions (PubMed:23213443). Defects in salivary gland invagination, migration and lumen shape and mislocalization of the integrin-binding protein rhea/Talin (PubMed:23862019). Defects in motor axon guidance with failure of motor axons to defasciculate from one another and innervate their proper muscle targets (PubMed:15282266). Wings display disrupted posterior crossveins (PubMed:26440503). RNAi-mediated knockdown in malpighian tubule principal cells inhibits NPLP1-4-mediated increases in fluid transport rates and cGMP levels, inhibits NPLP1-4-mediated nuclear translocation of NF-kappa-B protein Rel and abolishes expression of the antimicrobial peptide diptericin (PubMed:21893139). Belongs to the adenylyl cyclase class-4/guanylyl cyclase family.