The Mitogen-Activated Protein Kinase (MAPK) cascade is an essential pathway conserved from yeast to human. In C.elegans, the function of the MAPK pathway in vulval development is well characterized. The MAPK pathway has also been suggested to be important in olfaction (Nature 404:289). To study where it is expressed and what its role is there we generated an integrated line in which
mpk-1::GFP is expressed from its own promoter. Our result showed that MPK-1::GFP is expressed mostly in neurons in the nerve ring, ventral cord, tail and pharynx. The pharyngeal neurons NSM, M4, M5, MI, I2, I6 are stained. Consistent with the result from Takaaki Hirotsu et al, MPK-1::GFP is also expressed in olfactory neurons. ERK1 and ERK2, the mammalian homologues of MPK-1, are translocated from cytosol to nucleus by certain stimuli, where they phosphorylate nuclear targets. MPK-1::GFP is more concentrated in the cytoplasm than in the nucleus in most cells, and some neurons show exclusively cytoplasmic staining. We are searching for conditions in which
mpk-1 changes its location. In parallel, we are examining the regulation of
mpk-1 by western blotting with an MPK-1 antibody against phosphorylated ERK1/2 antibody. Based on the fact that a muscarinic receptor can signal through MAPK pathway in mammalian neurons, we treated worms with acetylcholine agonists, arecoline, but we couldn't see a big change of subcellular localization of MPK-1. We are also examining whether the MPK-1::GFP construct can complement an
mpk-1 null mutation.