The Ras-MAPK pathway is important for olfaction in Caenorhabditis elegans

Abstract

The Ras-MAPK (mitogen-activated protein kinase) signal transduction pathway is well known to control cellular proliferation and differentiation in response to extracellular signals, but its other functions are less understood. In Caenorhabditis elegans this pathway regulates several developmental events, such as vulval induction and progression of meiosis, but its function in the nervous system is unknown. Here we report that the Ras-MAPK pathway is involved in olfaction in this organism. Mutational inactivation and hyperactivation of this pathway impairs efficiency of chemotaxis to a set of odorants. Experiments in which let-60 ras was expressed using a heat-shock promoter and a cell-specific promoter show that a normal activity of LET-60 Ras is required in mature olfactory neurons. Application of the odorant isoamylalcohol to wild-type animals leads to the activation of MAP kinase in olfactory neurons within 10 seconds. This induction is dependent on the function of the nucleotide-gated channel TAX-2/TAX-4 and the voltage-activated calcium channel subunit UNC-2. These results suggest a dynamic regulatory role for the Ras-MAPK pathway in perception and transmission of sensory signals in olfactory neurons.

Odorants Stimulate the ERK/Mitogen-activated Protein Kinase Pathway and Activate cAMP-response Element-mediated Transcription in Olfactory Sensory Neurons

“…Interestingly, genetic mutation of the Ras homologue LET-60 Ras disrupts chemotaxis in Caenorhabditis elegans, suggesting that ERK/MAP kinase may contribute to olfactory detection in simpler organisms (50). In contrast to our study with mice that demonstrated odorant stimulation of ERK/MAP kinase maximally at 5 min, odorant stimulation of ERK/MAP kinase in C. elegans occurs within seconds.…”

Exocyst Subunits Exo70 and Exo84 Cooperate with Small GTPases to Regulate Behavior and Endocytic Trafficking in C. elegans

“…The let-60 gene acts genetically downstream of let-23 with respect to vulva development and upstream of the MAPK pathway with respect to chemotaxis [46], [47]. The rab-1 , rab-6.2 , rab-28 and rab-37 have all been shown in other model systems to regulate intracellular membrane trafficking.…”

Light and pheromone-sensing neurons regulates cold habituation through insulin signalling in Caenorhabditis elegans

“…2e include tax-4 cDNA that was PCR amplified from pDEST- tax-4cDNA (a gift from Dr Iino)35 and the 3′-untranslated region of unc-54 . In addition, pTOM4 includes the ASJ-specific trx-1 promoter (1.0 kb)36, which was from pQZ37 trx-1p::ICE (a gift from Dr Alcedo).…”