ZHENG, J.*; LEE, C.-Y.; WATSON, R.D.; University of Alabama at Birmingham; National Changhua Univ. of Education, Taiwan, ROC; University of Alabama at Birmingham: Molecular Cloning of a Putative Receptor Guanylyl Cyclase From Y-Organs of the Blue Crab, Callinectes sapidus

Crustacean molt-inhibiting hormone (MIH), a polypeptide produced by neurosecretory cells in eyestalk ganglia, suppresses the synthesis of ecdysteroid molting hormones by paired Y-organs. Data from several labs indicate the effects of MIH are mediated, at least in part, by a cGMP second messenger. Based on these and related findings, our working hypothesis is that the MIH receptor is a receptor guanylyl cyclase (rGC). In studies reported here, we used a PCR-based cloning strategy (RT-PCR followed by 5′- and 3′-RACE) to clone from blue crab (Callinectes sapidus) Y-organs a cDNA (CsGC-YO1) encoding a putative rCG. DNA sequence analysis revealed a 3792 base pair open reading frame encoding a 54 residue signal peptide and a 1210 residue rGC. Analysis of the deduced amino acid sequence showed that CsGC-YO1 contains the signature domains characteristic of rGCs, including an extracellular ligand-binding domain, a single transmembrane domain, an intracellular kinase-like domain, and an intracellular cyclase catalytic domain. CsGC-YO1 is most closely related to an rGC from the crayfish, Procambarus claikii (PcGC-M2, 58.4% identity), and rGCs from three insect species (33.1 – 37.5% identity). Conserved cysteine residues are similarly distributed in the extracellular domains of CsGC-YO1, PcGC-M2, and the three insect rGCs. RT-PCR revealed the CsGC-YO1 transcript is strongly expressed in Y-organs and several other tissues, including thoracic ganglion, nerve cord, and muscle. We hypothesize the cloned cDNA encodes an MIH receptor. Supported by the National Science Foundation (IBN-0213047) and the National Science Council, Taiwan, Republic of China (fellowship 39175F and grant NSC-91-2311-B-018-002).