生物谷報(bào)道：肌肉收縮通常發(fā)生在神經(jīng)遞質(zhì)分子從神經(jīng)細(xì)胞釋放到肌肉細(xì)胞的時(shí)候，然而來(lái)自美國(guó)猶他州大學(xué)的研究人員卻發(fā)現(xiàn)裸露的次原子：質(zhì)子能像大型的,，復(fù)雜的神經(jīng)遞質(zhì)一樣導(dǎo)致微小圓蠕蟲(chóng)（線蟲(chóng)）內(nèi)臟肌肉的收縮,。這一研究成果今天公布在Cell（1月11日）雜志上。
領(lǐng)導(dǎo)這一研究的是生物學(xué)家Erik Jorgensen,，猶他州大學(xué)大腦研究院科學(xué)主任,。Jorgensen表示，“細(xì)胞內(nèi)只有少數(shù)幾種分子能作為神經(jīng)遞質(zhì)啟動(dòng)電位變化,，質(zhì)子是將近20年以來(lái)這一家族的新成員,。”
（圖片來(lái)自Wayne Davis, University of Utah）
傳統(tǒng)的神經(jīng)遞質(zhì)，譬如serotonin, dopamine和GABA,，都是由許多原子組成,，這一新研究揭示了一個(gè)令人驚訝的發(fā)現(xiàn)：質(zhì)子——失去電子的單個(gè)氫原子——能從一種圓蠕蟲(chóng)的內(nèi)臟中通過(guò)某種蛋白釋放出來(lái)，結(jié)合在鄰近肌肉的受體蛋白上,，導(dǎo)致肌肉收縮,，從而引起蠕蟲(chóng)排便。
研究人員不僅發(fā)現(xiàn)質(zhì)子能像神經(jīng)遞質(zhì)一般工作,，而且識(shí)別出了在蠕蟲(chóng)這一過(guò)程中的基因和蛋白,，之前的研究表明人類和小鼠的大腦也具有能幫助質(zhì)子在細(xì)胞間移動(dòng)的質(zhì)子泵（proton pumps，生物谷注）和受體,，而這一新研究則進(jìn)一步發(fā)現(xiàn)這些質(zhì)子也許能作為大腦中的傳遞神經(jīng)信號(hào)因子,。
（圖片上部為一正常線蟲(chóng)，下部為大便干燥的線蟲(chóng),，箭頭指向線蟲(chóng)的內(nèi)臟,，圖片來(lái)自Paola Nix, University of Utah）
另一研究員Wayne Davis表示，“這是第一次發(fā)現(xiàn)質(zhì)子能作為神經(jīng)遞質(zhì)”,，“在人類可能也存在這些過(guò)程,，人類和小鼠大腦和內(nèi)臟細(xì)胞中有質(zhì)子泵，其中一些被認(rèn)為能幫助內(nèi)臟消化食物,，那么大腦中的質(zhì)子泵用來(lái)干嘛呢,？”
Jorgensen補(bǔ)充道，“缺乏質(zhì)子受體的小鼠不具有學(xué)習(xí)能力,，可能就是由于學(xué)習(xí)需要質(zhì)子泵和受體的幫助,。”
生物谷推薦原始出處：
Copyright © 2008 Cell Press. All rights reserved.
Cell, Vol 132, 149-160, 11 January 2008
Article
Protons Act as a Transmitter for Muscle Contraction in C. elegans
Asim A. Beg,1,2,3 Glen G. Ernstrom,2 Paola Nix,2 M. Wayne Davis,2 and Erik M. Jorgensen1,2,
1 Neuroscience Program, University of Utah, Salt Lake City, UT 84112-0840, USA
2 Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112-0840, USA
Corresponding author
Erik M. Jorgensen
jorgensen@biology.utah.edu
Muscle contraction is normally mediated by the release of neurotransmitters from motor neurons. Here we demonstrate that protons can act as a direct transmitter from intestinal cells to stimulate muscle contraction. During the C. elegans defecation motor program the posterior body muscles contract even in the absence of neuronal inputs or vesicular neurotransmission. In this study, we demonstrate that the space between the intestine and the muscle is acidified just prior to muscle contraction and that the release of caged protons is sufficient to induce muscle contraction. PBO-4 is a putative Na+/H+ ion exchanger expressed on the basolateral membrane of the intestine, juxtaposed to the posterior body muscles. In pbo-4 mutants the extracellular space is not acidified and the muscles fail to contract. The pbo-5 and pbo-6 genes encode subunits of a “cys-loop” proton-gated cation channel required for muscles to respond to acidification. In heterologous expression assays the PBO receptor is half-maximally activated at a pH of 6.8. The identification of the mechanisms for release and reception of proton signals establishes a highly unusual mechanism for intercellular communication.
