Wenjau Lee

2005年08月22日(月) 17:00 より 18:30 まで

明大寺地区１階会議室（１１１）

生殖生物学研究部門 大久保範聡 内線7554 okubo@nibb.ac.jp

The bag cell neurons (BCNs) of the mollusk Aplysia californicaprovide a simple model system for investigating cellular and molecular events regulating synthesis and secretion of a reproductive neuropeptide and their impact on physiology and behavior. The BCNs secrete a large amount of egg-laying hormone (ELH) in response to an electrical afterdischarge. The afterdischarge also triggers cellular and molecular events leading to increased ELH biosynthesis to replenish the supply of releasable hormone that was lost because of secretion. The increase in ELH synthesis is caused by upregulating translation of ELH mRNA rather than by activating ELH gene transcription, and is accompanied by a decrease in total protein synthesis. This suggests that the synthetic machinery is being funneled selectively toward ELH. The afterdischarge-induced ELH synthesis uses a novel mechanism of translation initiation, one involving a switch from cap-dependent to cap-independent translation initiation that activates an internal ribosome entry site (IRES) located in the 5’-untranslated region of ELH mRNA. The IRES-regulated translation provides a unique cellular mechanism to selectively upregulate synthesis of a critical reproductive hormone at the expense of nonessential proteins.