Worm Breeder's Gazette 14(3): 41 (June 1, 1996)

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.

An activating mutation in the G protein gene gsa-1 results in neural degeneration

Hendrik C. Korswagen1, Jong-Hyuk Park2, Yasumi Ohshima2, Ronald H.A. Plasterk1

1 Division of Molecular Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
2 Department of Biology, Faculty of Science, Kyushu University, Hakozaki, Fukuoka 812, Japan

Heterotrimeric G proteins relay information from transmembrane receptors to various intracellular effector systems. We cloned a C. elegans homolog of Gsalpha, the G protein alpha-subunit gene that couples to adenylate cyclase. gsa- 1 encodes a 375 amino acid protein that is 66% identical to rat Gsalpha. A gsa-1 GFP reporter construct is expressed throughout the nervous system and in muscle cells, including body wall muscles, the pharyngeal muscle cells and the muscle cells of the vulva. gsa-1 is an essential gene; loss of function of gsa-1 results in larval lethality. Animals homozygous for the deletion allele gsa-1(pk75) arrest in the first stage of larval development.

We analyzed the effects of a dominant activating mutation of gsa-1. To generate a constitutively active mutation in gsa-1, we mutated a conserved glutamine to a leucine (Q208L) in the gsa-1 sequence. This mutation destroys the GTPase activity of the G protein and locks it in the active state. Introduction of this dominant active gsa-1QL construct in transgenic animals results in lethality of the F1 transformants. Animals show vacuoles at the positions of neurons in the ventral nerve cord, the nerve ring and neurons in the tail. In addition, there is a strong hypercontraction of body wall muscle cells. Identical phenotypes are produced by expression of gsa-1QL under heat-shock promotor control. The phenotype of the vacuolated neurons is similar to the neural degeneration observed in the degenerin ion channel mutants, suggesting that gsa- 1QL activates ion channels and that an ion imbalance leads to the observed vacuolated neurons. The dominant degenerin channel mutations are suppressed by loss of function mutations in mec-6(e1342). We tested if mec-6 could also suppress the neural degeneration of gsa-1QL. mec- 6;gsa-1QL double mutants still show the gsa-1QL induced neural degeneration. Therefore, gsa-1QL may not act via degenerin type ion channels.

Suppressor screens and pharmacological studies to identify the possible gsa-1QL activated ion channels are in progress.