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Comments on Kenneth G Johnson et al. (2005) International Worm Meeting "Modulation of Ras signaling by the lipid transfer/exchange protein, CGR-1" (0)
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Kenneth G Johnson, Jessica Goldstein, Danielle Glossip, & Kerry Kornfeld (2005). Modulation of Ras signaling by the lipid transfer/exchange protein, CGR-1 presented in International Worm Meeting. Unpublished information; cite only with author permission.
The development of the Caenorhabditis elegans vulva requires the activity of the RAS signaling pathway. To identify components of this pathway, we screened for mutations that suppress the multivulval phenotype caused by let-60(n1046gf), a mutation that constitutively activates RAS. Forty-three alleles comprising 20 complementation groups were identified. One of these alleles, n2528, defines a novel complementation group on chromosome X. The n2528 mutation strongly suppressed the let-60(n1046gf) multivulval phenotype, but did not suppress the lin-1(n383) multivulval phenotype, suggesting that the affected gene may act downstream of let-60 ras but upstream of the lin-1 ETS transcription factor to promote RAS signaling. We mapped the n2528 mutation to an 18kb region that encompasses three predicted genes, one of which contained a G/A change generating a Proline to Leucine substitution in the predicted open reading frame of a CRAL/TRIO and GOLD domain-containing protein. A deletion (am114) spanning most of the CRAL/TRIO domain and half of the GOLD domain of this gene, identified using a PCR -based strategy in TMP-treated wild-type hermaphrodites, also caused a suppression of the Muv phenotype of the let-60(n1046gf) gene. In a wild-type genetic background, neither mutation dramatically affects vulval development, but do cause a temperature sensitive larval lethal phenotype; at 15oC, 100 percent of the am114 mutants die in the L1/L2 stage with a scrawny phenotype. This lethality appears to be distinct from the lethality associated with excretory duct cell development, and suggests a novel RAS-dependent developmental process. A mammalian homologue of CGR-1 enhances RAS signaling when overexpressed in vertebrate cells, and colocalizes with both RAS and RAF at peripheral sites of cell ruffling. These studies suggest that CGR-1 proteins have an evolutionarily conserved function in promoting RAS signaling.
Affiliation:
- Mol. Biol. and Pharm., Washington University, St Louis, MO.