Worm Breeder's Gazette 15(4): 32 (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
The c-Jun NH2-terminal kinase (JNK) belongs to a subgroup of the mitogen-activated protein kinase (MAPK) superfamily and is activated in response to a variety of stresses and cytokines in mammalian cells. To gain insight into the JNK cascade, we have undertaken a genetic analysis of the JNK signaling pathway in C. elegans. The genes for the C. elegans homolog of JNK, jnk-1 (formerly named sak-1), and its direct activator, jkk-1 (formerly named sek-2), were isolated based on their abilities to function in the yeast Hog1 MAP kinase pathway. JKK-1 is a novel member of the MAP kinase kinase (MAPKK) superfamily. Both jnk-1 and jkk-1 are expressed in most neurons. To understand the role of JKK-1, we isolated a jkk-1 deletion allele that lacks most of the kinase domains. If JKK-1 functions as MAPKK of JNK-1 in C. elegans, the latter should not be activated in jkk-1 mutant animals. To test this possibility, we examined the kinase activity of JNK-1 immunoprecipitated from wild-type and mutant animals. After immunoprecipitating JNK-1 from extracts of wild-type adults with an anti-JNK-1 antibody, we performed in vitro kinase assays using c-Jun as a substrate. JNK-1 prepared from wild-type animals phosphorylated c-Jun. However, JNK-1 immunoprecipitated from jkk-1 mutant adults exhibited little kinase activity. These results indicate that JNK-1 activity is positively regulated by JKK-1, supporting the idea that they constitute part of a functional JNK cascade. jkk-1 mutants were viable, but exhibited defects in body movement. Wild-type C. elegans moves by propagating waves of alternating dorsal and ventral flexions along its body length, which produces regular sinusoidal tracks on a bacterial lawn. In contrast, the mutant animals left tracks with increased amplitude relative to those left by the wild type. Paths also meandered more, seldom running in a straight trajectory for a long distance, and resulting in a much shorter migration distance during a given period of time. Other behaviors, including pharyngeal pumping, egg laying, and defecation, were normal in jkk-1 mutants. Thus, JKK-1 is specifically involved in the modulation of coordinated locomotion. To determine whether the locomotion defects are due to abnormal development or abnormal cell function, we generated a plasmid which places the jkk-1 gene under the control of heat-shock promoter and integrated it to the jkk-1 strain. These transgenic mutants were defective in movement without heat treatment. When heat-treated as adults, the movement defects were rescued. These results suggest that the movement defects are not due to a developmental abnormality, but rather to a defect in neuronal cell function. Thus, the JNK pathway modulates coordinated movement in C. elegans as a result of its role in neuronal function.