為什么膝關(guān)節(jié)或者肘關(guān)節(jié)彎曲時，四肢的神經(jīng)系統(tǒng)伸展，但不會被拉破？猶他州立大學(xué)的研究人員解釋了其中的奧妙,，他們發(fā)現(xiàn)一種彈力蛋白可以維持神經(jīng)細(xì)胞的韌性。
研究人員發(fā)現(xiàn),，線蟲體內(nèi)該蛋白基因如果受到破壞,，神經(jīng)細(xì)胞也會破壞。這項發(fā)現(xiàn)為第5型脊髓小腦共濟失調(diào)（spinocerebellar ataxia type 5,，SCA5）提供了研究的參考基礎(chǔ),。
SCA5是一種可能發(fā)生于各年齡層的神經(jīng)退化性疾病,，患者大腦中控制運動的神經(jīng)細(xì)胞受到破壞，患者發(fā)生行走,、談話,、寫作和吞咽的障礙，甚至需要借助輪椅度過余生,。研究結(jié)果刊載于1月29日的Cell Biology中,。
這項研究核心是一種名為unc-70的線蟲基因，unc-70轉(zhuǎn)譯的蛋白名為β血影蛋 白（beta spectrin）,。人類共有四個β血影蛋白基因,，每一個發(fā)生突變都會引起SCA5。
過去,，研究人員認(rèn)為,，SCA5的病因是突變的β血影蛋白無法與神經(jīng)細(xì)胞中特殊位置的其它蛋白結(jié)合，而導(dǎo)致細(xì)胞無法正常地傳遞訊息,。但是在線蟲進(jìn)行的新研究證實，真正的原因是由于突變的β血影蛋白引起的神經(jīng)細(xì)胞損傷,。
研究人員發(fā)現(xiàn)線蟲β血影蛋白突變后,，線蟲的神經(jīng)元容易破裂；β血影蛋白如同微型彈簧,，包被在神經(jīng)細(xì)胞中,，賦予神經(jīng)細(xì)胞伸展性。他們認(rèn)為突變基因可能與其它神經(jīng)退化性疾病,，如中風(fēng),、運動損傷引發(fā)的大腦損傷有關(guān)。所以保護(hù)神經(jīng)細(xì)胞中的血影蛋白,，似乎能夠減緩一些神經(jīng)退化性疾病的惡化速度,。
(資料來源 : Bio.com)
Nervous breakdown
An axon (arrow) snaps (top to bottom) in a worm lacking ß-spectrin
( 生物谷配圖)
更多生物圖片請進(jìn)入
Like the waistband of your pants after Thanksgiving dinner, neurons have to be able to stretch and then return to shape. On page 269 Hammarlund et al. pinpoint the protein that confers this springiness, showing that neurons lacking the molecule fracture.
Movements such as bending your elbow put strain on neurons, but the source of the cells' elasticity has been a mystery. Hammarlund et al. suspected that the protein ß-spectrin was involved. In red blood cells, the protein weaves into a mesh that supports the cell membrane, enabling erythrocytes to rebound after being crushed and dented during their travels through the circulatory system.
The researchers tested spectrin's function in neurons by observing nematodes that lack the protein. In embryonic worms, neurons grew normally between the animals' two nerve cords, indicating that spectrin isn't necessary for development. But after the worms hatched, their neurons began to display defects such as abnormal branching, frequent breaks, and signs of new growth, which doesn't normally occur after the embryonic stage. By tracking individual neurons, the scientists demonstrated that the breaks came first; the aberrant growth and misguided branches followed as worms attempted to repair the severed cells.
To determine whether movement snaps the neurons, the researchers scrutinized paralyzed animals. Few of their neurons broke. Hammarlund et al. conclude that the fragility of spectrin-lacking neurons might explain some kinds of neurodegenerative diseases. For example, patients with spinocerebellar ataxia type 5—an inherited form of paralysis that ran in Abraham Lincoln's family—carry a faulty ß-spectrin gene. Neurons might deteriorate in these patients because they break first, the researchers suggest.
