A NOVEL NEUROPEPTIDE, HYM-176, INDUCES CONTRACTION OF THE ECTODERMAL MUSCLE IN HYDRA

During the course of a systematic non-targeting screening of peptide s ignal molecules in Hydra, we identified a novel myoactive neuropeptide called Hym-176. The primary structure of Hym-176 was determined to be APFIFPGPKV amide. It specifically and reversibly induced contraction of the ectodermal muscle of the hydra body column in vivo. However, it had no effect on the ectodermal muscle of the tentacles. The structur e-activity relationship analysis showed that the sequence of FIFPGPKV amide is a minimal requirement for the myoactivity. Removal of an amid e group from the C-terminus completely abolished the activity. By usin g the antibody specific to Hym-176, the tissue localization of the pep tide in hydra was determined immunohistochemically. The intense immuno reactivity was found in the peduncle nerve cells, indicating that Hym- 176 is a neuropeptide. (C) 1998 Academic Press.