ペプチド作動性Na+チャネルの活性化とイオン透過性を制御する機能部位 <学位論文要旨>

Functional sites controlling the activation and ion permeation of a peptide-gated Na+ channel <Summaries of the Doctoral Theses>

Kodani Yu

広島大学大学院総合科学研究科紀要. I, 人間科学研究

Bulletin of the Graduate School of Integrated Arts and Sciences, Hiroshima University. I, Studies in human sciences

Peptides are ubiquitous signaling molecules in animals. Most of the peptide receptors identified so far are G protein-coupled receptors, but peptide-gated Na+ channels have also been cloned. This study investigated the structurefunction relationship of a peptide(FMRFamide)- gated Na+ channel (FaNaC). We focused on three polar residues (Y548, D552, D556) around the outer end of the second transmembrane domain of FaNaC. Site-directed mutagenesis and cysteine modification experiments uncovered that D552 is a critical determinant for various functional aspects of FaNaC, such as activation and desensitization kinetics, apparent FMRFamide sensitivity, channel block by FMRFamide, and current rectification. Double-mutant cycle analysis demonstrated that the interaction between D552 and Y548 regulates both activation and desensitization processes. Although point mutants in D556 were nonfunctional, a double mutant D552N/D556N was functional and showed markedly slow current kinetics. External Ca2+ inhibited the activation and desensitization of FaNaC. These Ca2+ actions were diminished by removal of the negative charge of D552, and notably, the Ca2+ action on desensitization was completely abolished in D552N/D556N, suggesting that D552 and D556 are involved in the Ca2+-binding site. In summary, Y548, D552, and D556 are important sites controlling the gating of FaNaC, and D552 also affects the ion permeation of the channel.

Biology [ 460 ]

jpn

広島大学大学院総合科学研究科

Copyright (c) 2012 by Graduate School of Integrated Arts and Sciences, Hiroshima University All rights reserved

[ISSN] 1881-7688

[NCID] AA12198647