In mammals, CREB and its closely related family members are widely expressed transcription factors that bind to CRE (cAMP-responsive element) in the regulatory region of many stimuli-responsive genes, and activated by the extracellular signals such as neurotransmitters and growth factors. CREB activity is regulated by phosphorylation on serine residue Ser133 (corresponding to Ser29 of C. elegans CRH-1beta). There are several candidates for stimulus-dependent CREB kinases including PKA, CaM-KI, II and IV, MAPKAP kinase, Akt/PKB etc. Orthologous genes which seems to encode counterparts of these kinases exist in C. elegans genome. We identified C.elegans orthologue of CREB (
crh-1 ) and its upstream kinases CaM-KI(
cmk-1 ) and CaM-KK(
ckk-1 ), and demonstrated that they constituted a signaling cascade analogous to mammalian system by biochemical analyses and in transfected cells. All of these genes are expressed in the several pharyngeal neurons. In order to examine the function of this signaling cascade in vivo , we generated transgenic worms carrying p CRE::GFP monitoring vector. Whereas, worms carrying only this vector showed weak fluorescence in small number of neurons, transgenic worms expressing either constitutively-active or Ca 2+ -independent form of
cmk-1 showed enhanced CRE-GFP expression. Furthermore,
crh-1 -deficeient worms exhibited extremely reduced GFP fluorescence, suggesting that
crh-1 is a main activator of CRE-genes in C. elegans. Introduction Ca 2+ -independent form of
cmk-1 with T179A mutation did not induce the CRE::GFP fluorescence and also
ckk-1 -deficient worm expressing Ca 2+ -independent form of
cmk-1 did not show the enhanced GFP-expression, indicating that
ckk-1 is absolutely required for
cmk-1 -mediated transcriptional activation through phosphorylation of. These results indicate that CaM-KK/CaM-K/CREB cascade is conserved and operated in the several neurons of C. elegans . We are further trying to analyze the roles of MAPK and PKA signaling pathways on CREB activation in several neurons in C. elegans