A Caenorhabditis elegans MAP kinase kinase, MEK-1, is involved in stress responses

The c-Jun N-terminal kinase (JNK), a member of the mitogen-activated protei n kinase (MAPK) family, was shown to be involved in the response to various stresses in cultured cells. However, there is little in vivo evidence indi cating a role for a JNK pathway in the stress response of an organism. We i dentified the Caenorhabditis elegans mek-1 gene, which encodes a 347 amino acid protein highly homologous to mammalian MKK7, an activator of JNK, Mek- 1 reporter fusion proteins are expressed in pharyngeal muscle, uterus, a po rtion of intestine, and neurons. A mek-1 deletion mutant is hypersensitive to copper and cadmium ions and to starvation. A wild-type mek-1 transgene r escued the hypersensitivity to the metal ions. Double mutants of mek-1 with an eat-5, eat-II or eat-18 mutation, which are characterized by a limited feeding defect, showed distinct growth defects under normal conditions. Exp ression of an activated form of MEK-1 in the whole animal or specifically i n the pharynx inhibited pharyngeal pumping. These results suggest a role fo r mek-1 in stress responses, with a focus in the pharynx and/or intestine.