Worm Breeder's Gazette 15(4): 30 (October 1, 1998)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, JAPAN
JNK and p38 belong to a subgroup of the mitogen-activated protein kinase (MAPK) superfamily and are activated in response to a variety of stresses in mammalian cells. SEK1/MKK4 is known to activate both JNK and p38 MAPKs as MAPK Kinase. We have identified a protein kinase, SEK-1, which has significant similarity with mammalian SEK1. SEK-1 can activate both of C. elegans JNK homolog JNK-1 and p38 homologs PMK-1 and PMK-2 in yeast Hog1 MAPK system. These results suggested that SEK-1 has substrate specificity similar to mammalian SEK1. To determine the SEK-1 expression pattern, we generated the animals carrying sek-1::gfp transcriptional fusion constructs. In L1 stage larvae, SEK-1::GFP was expressed in many cells including excretory/secretory cells, enteric muscles, procorpus in pharynx, AVA, AVD, AVE and unidentified neurons. SEK-1::GFP was also expressed in Uterine muscles and Vulval muscles in the adult. To investigate the function of SEK-1, we generated a sek-1 deletion mutant which lacks most of protein kinase catalytic domains. The sek-1 mutant animals did not show obvious developmental defects, but were defective in egg-laying and formed bag-of-worms (penetrancy>90%). Young sek-1 mutant adults responded partially to serotonin but were completely resistant to imipramine in egg-laying. These data suggest that the egl-d phenotype associated with sek-1 deletion is at least caused by defects in the sex muscles and possibily by defects in the secretion of Serotonin from neurons. In order to identify proteins directly involved in SEK-1 function, we screened for SEK-1 binding proteins using an yeast two-hybrid system. We isolated a new cDNA, termed seb-1 (sek-1 binding protein-1), whose product belongs to synaptotagmin family. SEB-1 also interacted JNK-1 by two-hybrid system. Synaptotagmin is an integral membrane protein and important for vesicle transporting including synaptic exocytosis. One possibility is that a SEB-1 may function to anchor both of SEK-1 and JNK-1 to the membrane.