Finkelstein Erik I, Chao Pen-hsiu Grace, Hung Clark T, Bulinski Jeannette Chloë
Department of Biological Sciences, Columbia University, New York, New York, USA.
Cell Motil Cytoskeleton. 2007 Nov;64(11):833-46. doi: 10.1002/cm.20227.
Galvanotaxis, that is, migration induced by DC electric fields, is thought to play a significant role in development and wound healing, however, the mechanisms by which extrinsic electric fields orchestrate intrinsic motility responses are unknown. Using mammalian cell lines (3T3, HeLa, and CHO cells), we tested one prevailing hypothesis, namely, that electric fields polarize charged cell surface molecules, and that these polarized molecules drive directional motility. Negatively charged sialic acids, which contribute the bulk of cell surface charge, redistribute preferentially to the surface facing the direction of motility, as measured by labeling with fluorescent wheat germ agglutinin. We treated cells with neuraminidase to remove sialic acids; as expected, this decreased total cell surface charge. We also changed cell surface charge independent of sialic acid moieties, by conjugating cationic avidin to the surface of live cells. Neuraminidase inhibited the electric field-induced directional polarization of membrane ruffling and alpha4 integrin, while avidin treatment actually reversed the directional polarization of sialic acids. Neuraminidase treatment inhibited directionality but did not alter speed of motility. Surprisingly, avidin treatment did not significantly alter either directionality or speed of motility. Thus, our results demonstrate that electric field-induced polarization of charged species indeed occurs. However, polarization of the bulk of charged cell surface proteins is neither necessary nor sufficient to cause motility, thus contradicting the second part of our hypothesis. Because neuraminidase inhibited directional motility, we also conclude that sialic acids are required constituents of some cell surface molecule(s) through which electric fields mount a polarized transmembrane response.
趋电性，即由直流电场诱导的迁移，被认为在发育和伤口愈合中发挥重要作用，然而，外在电场协调内在运动反应的机制尚不清楚。我们使用哺乳动物细胞系（3T3、HeLa和CHO细胞）测试了一个普遍的假设，即电场使带电荷的细胞表面分子极化，并且这些极化分子驱动定向运动。通过用荧光麦胚凝集素标记测量，对细胞表面电荷起主要作用的带负电荷的唾液酸优先重新分布到面向运动方向的表面。我们用神经氨酸酶处理细胞以去除唾液酸；正如预期的那样，这降低了细胞表面总电荷。我们还通过将阳离子抗生物素蛋白缀合到活细胞表面，独立于唾液酸部分改变细胞表面电荷。神经氨酸酶抑制电场诱导的膜 ruffling 和α4整合素的定向极化，而抗生物素蛋白处理实际上逆转了唾液酸的定向极化。神经氨酸酶处理抑制了方向性，但没有改变运动速度。令人惊讶的是，抗生物素蛋白处理既没有显著改变方向性也没有改变运动速度。因此，我们的结果表明确实发生了电场诱导的带电物质极化。然而，大部分带电荷的细胞表面蛋白的极化对于引起运动既不是必需的也不是充分的，因此与我们假设的第二部分相矛盾。因为神经氨酸酶抑制了定向运动，我们还得出结论，唾液酸是一些细胞表面分子的必需成分，电场通过这些分子产生极化的跨膜反应。
