Growth cone behavior and production of traction force.
Growth cone behavior and production of traction force.
复制标题
DOI：
10.1083/jcb.111.5.1949
复制
发表时间：
1990-11
期刊：
影响因子：
--
通讯作者：
Buxbaum RE
中科院分区：
文献类型：
--
作者：
Heidemann SR;Lamoureux P;Buxbaum RE
生长锥必须通过一些牵引力向后推动其基底，以推动自身向前。为了确定哪些生长锥行为产生牵引力，我们在环境中障碍物（即其他感觉神经元的神经突或玻璃纤维）的运动调节力产生的条件下观察了雏鸡的感觉生长锥。这些障碍物的运动通过三种不同的、刻板的生长锥行为发生：（a）丝状伪足收缩，（b）生长锥背表面上的平滑向后运动，以及（c）与褶皱片状伪足的相互作用。超过 70% 的障碍物运动是由丝状伪足收缩引起的，其中障碍物附着在丝状伪足的最远端，并且仅当丝状伪足改变其延伸时才移动。丝状收缩的特点是障碍物速度和方向的频繁变化。据估计，单个丝状足的收缩会产生 50-90 微达的力，这可以解释小鸡感觉生长锥所施加的拉力。重要的是，所有五个生长锥在障碍神经突顶部生长的情况（即，模仿通常生长锥/基质相互作用的几何形状）都是丝状收缩类型。大约 25% 的障碍物移动是通过沿着生长锥顶面平滑向后移动而发生的。运动的外观和速率与报告的背侧生长锥表面附近的皮质肌动蛋白逆行流动相似。尽管这些逆流运动也施加了足够的力来解释生长锥拉力，但我们没有在腹侧生长锥表面上观察到这种运动。有时，障碍物会因与褶皱片状伪足的相互作用而被移动。然而，我们没有获得任何证据表明障碍物附着在褶皱的片状伪足上或通过这种机制定向障碍物运动。这些数据表明，雏鸡感觉生长锥通过丝状伪足的收缩活动向前移动，即在刚性基质上进行等长收缩。我们的数据反对肌动蛋白逆行流动产生牵引力。
The growth cone must push its substrate rearward via some traction force in order to propel itself forward. To determine which growth cone behaviors produce traction force, we observed chick sensory growth cones under conditions in which force production was accommodated by movement of obstacles in the environment, namely, neurites of other sensory neurons or glass fibers. The movements of these obstacles occurred via three, different, stereotyped growth cone behaviors: (a) filopodial contractions, (b) smooth rearward movement on the dorsal surface of the growth cone, and (c) interactions with ruffling lamellipodia. More than 70% of the obstacle movements were caused by filopodial contractions in which the obstacle attached at the extreme distal end of a filopodium and moved only as the filopodium changed its extension. Filopodial contractions were characterized by frequent changes of obstacle velocity and direction. Contraction of a single filopodium is estimated to exert 50-90 microdyn of force, which can account for the pull exerted by chick sensory growth cones. Importantly, all five cases of growth cones growing over the top of obstacle neurites (i.e., geometry that mimics the usual growth cone/substrate interaction), were of the filopodial contraction type. Some 25% of obstacle movements occurred by a smooth backward movement along the top surface of growth cones. Both the appearance and rate of movements were similar to that reported for retrograde flow of cortical actin near the dorsal growth cone surface. Although these retrograde flow movements also exerted enough force to account for growth cone pulling, we did not observe such movements on ventral growth cone surfaces. Occasionally obstacles were moved by interaction with ruffling lamellipodia. However, we obtained no evidence for attachment of the obstacles to ruffling lamellipodia or for directed obstacle movements by this mechanism. These data suggest that chick sensory growth cones move forward by contractile activity of filopodia, i.e., isometric contraction on a rigid substrate. Our data argue against retrograde flow of actin producing traction force.