Caenorhabditis elegans SOS-1 is necessary for multiple RAS-mediated developmental signals

Abstract

Vulval induction in Caenorhabditis elegans has helped define an evolutionarily conserved signal transduction pathway from receptor tyrosine kinases (RTKs) through the adaptor protein SEM‐5 to RAS. One component present in other organisms, a guanine nucleotide exchange factor for Ras, has been missing in C.elegans. To understand the regulation of this pathway it is crucial to have all positive‐acting components in hand. Here we describe the identification, cloning and genetic characterization of C.elegans SOS‐1, a putative guanine nucleotide exchanger for LET‐60 RAS. RNA interference experiments suggest that SOS‐1 participates in RAS‐dependent signaling events downstream of LET‐23 EGFR, EGL‐15 FGFR and an unknown RTK. We demonstrate that the previously identified let‐341 gene encodes SOS‐1. Analyzing vulval development in a let‐341 null mutant, we find an SOS‐1‐independent pathway involved in the activation of RAS signaling. This SOS‐1‐independent signaling is not inhibited by SLI‐1/Cbl and is not mediated by PTP‐2/SHP, raising the possibility that there could be another RasGEF.

Additional details