Worm Breeder's Gazette 15(2): 46 (February 1, 1998)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Sussex Centre for Neuroscience, University of Sussex, Falmer, Brighton, England. BN1 9QG
Cyclic GMP (cGMP) is an important intracellular signaling molecule in both vertebrates and invertebrates mediating a number of important physiological roles such as cardiovascular tone, neuronal signalling, platelet function and phototransduction (Hobbs, 1997). cGMP is synthesized from GTP by the enzyme guanylate cyclase (GC) which has two main classes; membrane bound or particulate GC (mGC) and the soluble, cytosolic form (sGC). The former generally mediate the action of signaling peptides such as atrial natriuretic peptide whereas sGC is the primary target of nitric oxide (NO), a gaseous intracellular messenger (Palmer et al, 1987). Around thirty GCs have been identified by the C. elegans genomic sequencing program to date (Yu et al,1997), with about five probable sGCs and the remainder being putative mGCs (most closely related to the mammalian natriuretic peptide receptors). We are interested in identifying and characterising the sGCs in C. elegans in terms of their expression, activation and physiological roles. We have already cloned and sequenced a cDNA corresponding to the putative sGC C06B3.8, now identified by Yu et al as gcy-32. By using a combination of RT-PCR and PCR amplification of a cDNA library, the clone was found to use two different polyadenylation signals and also shows a different splicing form to that predicted by the Genefinder software. It is not yet apparent whether this cDNA is trans-spliced. In other systems, sGC has been shown to function as a heterodimeric protein and work is under way to identify which genes are coexpressed in particular cells, using a combination of GFP fusion constructs and immunocytochemistry. A radioimmunoassay has been developed to detect cGMP generation in extracts of nematode tissue. Interestingly, worm cytosolic extract appears to be insensitive to NO stimulation. This is consistent with work carried out in our lab which has failed to demonstrate Ca2+ stimulated turnover of 3H-arginine to 3H-citrulline; a standard assay for NO production by the enzyme nitric oxide synthase (NOS). Also, no genes have yet been identified by the worm sequencing project which show homology to NOS. This has lead us to the intriguing possibility that C. elegans does not possess a classical NO-cGMP signaling pathway. Our ultimate goal is to prove or disprove this theory and to shed light on the physiological and behavioral role of the sGCs that have been found in the worm genome. References. Hobbs, A. J. (1997) Trends Pharmacol. Sci. 18, 484-491 Palmer, R. M. J., Ferridge, A. G. and Moncada, S. (1987) Nature 327, 524-526 Yu, S., Avery, L., Baude, E. and Garbers, D. L. (1997) Proc. Natl. Acad. Sci. U.S.A. 94, 3384-3387