Euteneuer U, Schliwa M
Institute for Cell Biology, University of Munich, Germany.
J Cell Biol. 1992 Mar;116(5):1157-66. doi: 10.1083/jcb.116.5.1157.
Locomoting cells are characterized by a pronounced external and internal anterior-posterior polarity. One of the events associated with cell polarization at the onset of locomotion is a shift of the centrosome, or MTOC, ahead of the nucleus. This position is believed to be of strategic importance for directional cell movement and cell polarity. We have used BSC-1 cells at the edge of an in vitro wound to clarify the causal relationship between MTOC position and the initiation of cell polarization. We find that pronounced cell polarization (the extension of a lamellipod) can take place in the absence of MTOC repositioning or microtubules. Conversely, MTOCs will reposition even after lamellar extension and cell polarization have occurred. Repositioning requires microtubules that extend to the cell periphery and is independent of selective detyrosination of microtubules extending towards the cell front. Significantly, MTOCs maintain, or at least attempt to maintain, a position at the cell's centroid. This is most clearly demonstrated in wounded monolayers of enucleated cells where the MTOC closely follows the centroid position. We suggest that the primary response to the would is the biased extension of a lamellipod, which can occur in the absence of microtubules and MTOC repositioning. Lamellipod extension leads to a shift of the cell's centroid towards the wound. The MTOC, in an attempt to maintain a position near the cell center, will follow. This will automatically put the MTOC ahead of the nucleus in the vast majority of cells. The nucleus as a reference for MTOC position may not be as meaningful as previously thought.
移动细胞的特征是具有明显的外部和内部前后极性。与运动开始时细胞极化相关的事件之一是中心体或微管组织中心（MTOC）向细胞核前方移动。这个位置被认为对细胞的定向运动和细胞极性具有战略重要性。我们利用体外伤口边缘的BSC-1细胞来阐明MTOC位置与细胞极化起始之间的因果关系。我们发现，在没有MTOC重新定位或微管的情况下，也能发生明显的细胞极化（片状伪足的延伸）。相反，即使在片状延伸和细胞极化发生后，MTOC仍会重新定位。重新定位需要延伸到细胞周边的微管，并且与向细胞前端延伸的微管的选择性去酪氨酸化无关。值得注意的是，MTOC维持或至少试图维持在细胞质心的位置。这在去核细胞的受伤单层中最为明显地表现出来，其中MTOC紧密跟随质心位置。我们认为，对伤口的主要反应是片状伪足的偏向延伸，这在没有微管和MTOC重新定位的情况下也能发生。片状伪足的延伸导致细胞质心向伤口移动。MTOC为了维持在细胞中心附近的位置，会随之移动。这将在绝大多数细胞中自动使MTOC位于细胞核前方。细胞核作为MTOC位置的参考可能不像以前认为的那么有意义。
