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.

The Physiological Roles of Soluble Guanylate Cyclase in Caenorhabditis elegans

Martin Lyn Hudson, Michael O'Shea

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

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.


Hobbs, A. J. (1997) Trends Pharmacol. Sci. 18, 484-491
Palmer, R. M. J., Ferridge, A. G. and Moncada, S. (1987) Nature 327,
Yu, S., Avery, L., Baude, E. and Garbers, D. L. (1997) Proc. Natl. Acad.
Sci. U.S.A. 94, 3384-3387