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.

Role of SEK-1 MAP Kinase Kinase in C.elegans

Miho Tanaka, Masato Kawasaki, Norio Suzuki, Naoki Hisamoto, Kunihiro Matsumoto

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.