Brown M J, Loew L M
Department of Physiology, University of Connecticut Health Center, Farmington 06030.
J Cell Biol. 1994 Oct;127(1):117-28. doi: 10.1083/jcb.127.1.117.
Directional cellular locomotion is thought to involve localized intracellular calcium changes and the lateral transport of cell surface molecules. We have examined the roles of both calcium and cell surface glycoprotein redistribution in the directional migration of two murine fibroblastic cell lines, NIH 3T3 and SV101. These cell types exhibit persistent, cathode directed motility when exposed to direct current electric fields. Using time lapse phase contrast microscopy and image analysis, we have determined that electric field-directed locomotion in each cell type is a calcium independent process. Both exhibit cathode directed motility in the absence of extracellular calcium, and electric fields cause no detectable elevations or gradients of cytosolic free calcium. We find evidence suggesting that galvanotaxis in these cells involves the lateral redistribution of plasma membrane glycoproteins. Electric fields cause the lateral migration of plasma membrane concanavalin A receptors toward the cathode in both NIH 3T3 and SV101 fibroblasts. Exposure of directionally migrating cells to Con A inhibits the normal change of cell direction following a reversal of electric field polarity. Additionally, when cells are plated on Con A-coated substrata so that Con A receptors mediate cell-substratum adhesion, cathode-directed locomotion and a cathodal accumulation of Con A receptors are observed. Immunofluorescent labeling of the fibronectin receptor in NIH 3T3 fibroblasts suggests the recruitment of integrins from large clusters to form a more diffuse distribution toward the cathode in field-treated cells. Our results indicate that the mechanism of electric field directed locomotion in NIH 3T3 and SV101 fibroblasts involves the lateral redistribution of plasma membrane glycoproteins involved in cell-substratum adhesion.
定向细胞运动被认为涉及局部细胞内钙变化和细胞表面分子的侧向运输。我们研究了钙和细胞表面糖蛋白重新分布在两种小鼠成纤维细胞系NIH 3T3和SV101定向迁移中的作用。当暴露于直流电场时，这些细胞类型表现出持续的、向阴极的运动性。使用延时相差显微镜和图像分析，我们确定每种细胞类型中电场导向的运动是一个不依赖钙的过程。在没有细胞外钙的情况下，两者都表现出向阴极的运动性，并且电场不会导致可检测到的胞质游离钙升高或梯度变化。我们发现有证据表明这些细胞中的电趋性涉及质膜糖蛋白的侧向重新分布。电场导致NIH 3T3和SV101成纤维细胞中质膜伴刀豆球蛋白A受体向阴极侧向迁移。将定向迁移的细胞暴露于伴刀豆球蛋白A会抑制电场极性反转后细胞方向的正常变化。此外，当细胞接种在包被有伴刀豆球蛋白A的基质上，使得伴刀豆球蛋白A受体介导细胞与基质的粘附时，可观察到向阴极的运动性和伴刀豆球蛋白A受体的阴极积累。对NIH 3T3成纤维细胞中纤连蛋白受体的免疫荧光标记表明，在电场处理的细胞中，整合素从大的簇中募集，形成向阴极更分散的分布。我们的结果表明，NIH 3T3和SV101成纤维细胞中电场导向运动的机制涉及参与细胞与基质粘附的质膜糖蛋白的侧向重新分布。
