Actin-dependent myoid elongation in teleost rod inner/outer segments occurs in the absence of net actin polymerization.
Actin-dependent myoid elongation in teleost rod inner/outer segments occurs in the absence of net actin polymerization.
复制标题
硬骨鱼杆内/外节中的肌动蛋白依赖性肌样伸长发生在缺乏净肌动蛋白聚合的情况下。
DOI：
10.1002/cm.970210307
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发表时间：
1992
影响因子：
--
通讯作者：
Burnside,B
中科院分区：
文献类型：
--
作者：
Pagh-Roehl,K;Brandenburger,J;Wang,E;Burnside,B
在硬骨鱼的视网膜中，杆状感光器对光的反应是拉长的。光激活的伸长是由杆内节段的肌样蛋白介导的，并依赖于肌动蛋白。内节F-肌动蛋白细丝形成平行于细胞长轴的束状排列。我们使用机械分离的杆片段来研究杆延长的机制，包括运动的内段和感觉的外段(RIS-ROS)。当RIS-ROS从适应深色的绿色太阳鱼中分离出来并在光照下培养时，它们以每分钟0.3-0.6min0.3-0.6min.的速度延长15min。0.1μM细胞松弛素D抑制细胞伸长65%，提示肌动蛋白组装是必需的。为了确定在伸长过程中的组装程度，我们使用了三种方法来测量RIS-ROS中F-肌动蛋白的含量：洗涤剂提取RIS-ROS后，用SDS-PAGE检测可丸化的肌动蛋白；用荧光法、荧光激活细胞分选和图像分析来定量荧光素-鬼笔环素结合；用电子显微镜估计F-肌动蛋白细丝的总长度。三种检测方法均表明，RIS-ROS F-肌动蛋白无净装配伴随肌样延长。伸长的肌样中F-肌动蛋白含量的增加被位于内节末端与生长的肌样突起相对的13个微绒毛样花萼突起中的F-肌动蛋白含量的减少所抵消。O‘Connor和Burnside(Journal of Cell Biology89：517-524,1981)指出，杆状F-肌动蛋白细丝的负端朝向伸长的肌样，而正端朝向缩短的花萼突起。我们的观察表明，RIS-ROS的延长需要肌动蛋白在细丝的负端进行聚合，并在细丝的正端进行解聚。
In the retinas of teleost fish, rod photoreceptors elongate in response to light. Light‐activated elongation is mediated by the myoid of the rod inner segment and is actin‐dependent. Inner segment F‐actin filaments form bundles running parallel to the cell's long axis. We examined the mechanism of rod elongation using mechanically‐detached rod fragments, consisting of the motile inner segment and sensory outer segment (RIS‐ROS). When RIS‐ROS are isolated from darkadapted green sunfish and cultured in the light, they elongate 15μm at 0.3–0.6μm/min. Elongation was inhibited 65% by 0.1μM Cytochalasin D, suggesting a requirement for actin assembly. To determine the extent of assembly during elongation, we used three approaches to measure the F‐actin content in RIS‐ROS: detection of pelletable actin by SDS‐PAGE after detergent‐extraction of RIS‐ROS; quantification of fluorescein‐phalloidin binding by fluorimetry, fluorescence‐activated cell sorting and image analysis; estimation of total F‐actin filament length by electron microscopy. All three assays indicated that no net assembly of RIS‐ROS F‐actin accompanied myoid elongation. An increase in F‐actin content within the elongated myoid was counterbalanced by a decrease in F‐actin content within the 13 microvillus‐like calycal processes located at the end of the inner segment opposite to the growing myoid. O'Connor and Burnside(Journal of Cell Biology89:517–524, 1981) showed that minus‐ends of rod F‐actin filaments are oriented towards the elongating myoid while plus‐ends are oriented towards the shortening calycal processes. Our observations suggest that RIS‐ROS elongation entails actin polymerization at the minus‐ends of filaments coupled with depolymerization at the filament plus‐ends.