Niu M Y, Mills J C, Nachmias V T
Department of Cell and Developmental Biology, School of Medicine, University of Pennsylvania, Philadelphia 19104-6048, USA.
Cell Motil Cytoskeleton. 1997;36(3):203-15. doi: 10.1002/(SICI)1097-0169(1997)36:3<203::AID-CM1>3.0.CO;2-8.
Cultured human erythroleukemia (HEL) cells were used to study the genesis of polarity in single cells. HEL cells grow in suspension in culture medium, but attach and spread on fibronectin when treated with 10 nM phorbol myristate acetate. If the spread cells are treated with dibutyryl cyclic adenosine monophosphate, about 50% of the cells polarize and form very striking elongated processes. Time-lapse video microscopy showed that elongation develops in these cells because the anterior pole of the cell, which bears a small ruffled membrane, moves slowly (approximately 0.16 microgram/min) forward on the substratum elongating the posterior pole or tail behind it. Using indirect immunofluorescence we found that elongation of the tail correlates with the development of long microtubule bundles emanating from the centrosome, which is located posterior to the nucleus on the trailing side of the cell. Incubation with nocodazole, which inhibited development of the long microtubules and the elongation, resulted in a centrosome positioned over the nucleus in 45% of the cells and extension of the membrane ruffling to many points around the cell's periphery. Unexpectedly, time-lapse video microscopy demonstrated that the treated cultures also contained some smaller cells with very marked anterior ruffles and short tails. These cells moved rapidly about the culture dish (maximum 0.8 microgram/min; average 0.5 microgram/min). In these fast moving cells the centrosome was also located posterior to the nucleus. Several recent reports have stressed the importance of relocation of the centrosome to an anterior position in cells developing polarity after experimental wounding. Our results show that both striking polarization and rapid motility can occur without such a relocation. The polarity induced in the HEL cells correlates most clearly with the limitation of membrane ruffling to one region; this limitation is removed by microtubule disassembly. We therefore propose that localized ruffling is the critical first step in polarized motility generally, and that centrosomal position is related to other factors.
培养的人红白血病（HEL）细胞被用于研究单细胞极性的起源。HEL细胞在培养基中悬浮生长，但在用10 nM佛波酯肉豆蔻酸酯乙酸盐处理后会附着并铺展在纤连蛋白上。如果对铺展的细胞用二丁酰环磷腺苷处理，约50%的细胞会极化并形成非常明显的细长突起。延时视频显微镜显示这些细胞中突起的形成是因为细胞的前极带有一个小的皱膜，它在基质上缓慢向前移动（约0.16微米/分钟），使后极或尾部在其后伸长。通过间接免疫荧光我们发现尾部的伸长与从位于细胞核后方、细胞尾侧的中心体发出的长微管束的形成相关。用诺考达唑处理抑制了长微管的形成和伸长，导致45%的细胞中中心体位于细胞核上方，并且膜皱襞延伸到细胞周边的许多点。出乎意料的是，延时视频显微镜显示处理后的培养物中还含有一些较小的细胞，它们具有非常明显的前皱襞和短尾巴。这些细胞在培养皿中快速移动（最大0.8微米/分钟；平均0.5微米/分钟）。在这些快速移动的细胞中，中心体也位于细胞核后方。最近的几份报告强调了在实验性创伤后细胞极性形成过程中中心体重新定位到前部位置的重要性。我们的结果表明，在没有这种重新定位的情况下也能发生明显的极化和快速运动。HEL细胞中诱导的极性与膜皱襞局限于一个区域最明显相关；这种局限通过微管拆卸被消除。因此我们提出局部皱襞通常是极化运动的关键第一步，并且中心体的位置与其他因素有关。
