Unconventional myosins in inner-ear sensory epithelia.
Unconventional myosins in inner-ear sensory epithelia.
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DOI：
10.1083/jcb.137.6.1287
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发表时间：
1997-06-16
期刊：
影响因子：
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通讯作者：
Corey DP
中科院分区：
文献类型：
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作者：
Hasson T;Gillespie PG;Garcia JA;MacDonald RB;Zhao Y;Yee AG;Mooseker MS;Corey DP
为了解细胞如何有差异地利用每个基因组中存在的数十种肌球蛋白同工酶，我们研究了四种非传统肌球蛋白同工酶在内耳中的分布，内耳是一种特别依赖富含肌动蛋白的结构和非传统肌球蛋白同工酶的组织。在这四种同工酶中，每种来自不同的类别，其中三种在两栖动物和哺乳动物的毛细胞中表达。在由交联的F - 肌动蛋白丝构成的静纤毛中，肌球蛋白 - Iβ主要位于静纤毛顶端附近，肌球蛋白 - VI基本不存在，而肌球蛋白 - VIIa与连接相邻静纤毛的交联结构共定位。在角质板（一种肌动蛋白丝网状结构）中，肌球蛋白 - Iβ不存在，肌球蛋白 - VI集中存在，且有适量的肌球蛋白 - VIIa。这三种肌球蛋白同工酶不存在于其他富含肌动蛋白的区域，包括环周肌动蛋白带和皮质肌动蛋白网络。第四类的一个成员，肌球蛋白 - V，不在毛细胞中表达，但在支配毛细胞的传入神经细胞中高水平存在。大量的肌球蛋白 - Iβ、 - VI和 - VIIa位于角质周项链结构中，该结构基本无F - 肌动蛋白，被挤压在角质板的肌动蛋白和环周带之间（但不与之相关联）。我们的定位结果表明三种毛细胞肌球蛋白同工酶具有特定功能。如先前所述，肌球蛋白 - Iβ可能在适应过程中起作用；肌球蛋白 - VI在角质板中聚集以及与静纤毛根丝的关联表明该同工酶参与牢固地固定静纤毛；最后，与相邻静纤毛之间交联结构的共定位表明肌球蛋白 - VIIa是毛束结构完整性所必需的。
To understand how cells differentially use the dozens of myosin isozymes present in each genome, we examined the distribution of four unconventional myosin isozymes in the inner ear, a tissue that is particularly reliant on actin-rich structures and unconventional myosin isozymes. Of the four isozymes, each from a different class, three are expressed in the hair cells of amphibia and mammals. In stereocilia, constructed of cross-linked F-actin filaments, myosin-Iβ is found mostly near stereociliary tips, myosin-VI is largely absent, and myosin-VIIa colocalizes with crosslinks that connect adjacent stereocilia. In the cuticular plate, a meshwork of actin filaments, myosin-Iβ is excluded, myosin-VI is concentrated, and modest amounts of myosin-VIIa are present. These three myosin isozymes are excluded from other actin-rich domains, including the circumferential actin belt and the cortical actin network. A member of a fourth class, myosin-V, is not expressed in hair cells but is present at high levels in afferent nerve cells that innervate hair cells. Substantial amounts of myosins-Iβ, -VI, and -VIIa are located in a pericuticular necklace that is largely free of F-actin, squeezed between (but not associated with) actin of the cuticular plate and the circumferential belt. Our localization results suggest specific functions for three hair-cell myosin isozymes. As suggested previously, myosin-Iβ probably plays a role in adaptation; concentration of myosin-VI in cuticular plates and association with stereociliary rootlets suggest that this isozyme participates in rigidly anchoring stereocilia; and finally, colocalization with cross-links between adjacent stereocilia indicates that myosin-VIIa is required for the structural integrity of hair bundles.