Chinkers M, McKanna J A, Cohen S
J Cell Biol. 1981 Feb;88(2):422-9. doi: 10.1083/jcb.88.2.422.
Epidermal growth factor (EGF) induces rapid rounding of A-431 human epidermoid carcinoma cells in Ca(++)-free medium. Cell rounding is not induced by a variety of other polypeptide hormones, antiserum to cell membranes, local anesthetics, colchicine, cytochalasin B, or cyclic nucleotides. However, trypsin, like EGF, induces rounding of A- 431 cells in the absence of Ca(++). Both trypsin- and EGF-induced rounding are temperature dependent, appear to be energy dependent, and are inhibited by cytochalasins, suggesting that the active participation of microfilaments in cell rounding. However, a medium transfer experiment suggests that EGF-induced rounding is not attributable to secretion of a protease, and a number of serine protease inhibitors have no effect on the EGF-induced rounding process. Cell rounding is not attributable to the slight stimulation by EGF of the release of Ca(++) that is observed in the Ca(++)-free medium, as stimulation of such release by the ionophore A23187 neither induces cell rounding nor blocks EGF-induced rounding. Cells that have rounded up after treatment with EGF or trypsin spread out upon addition of Ca(++) to the medium, even in the continuing presence of EGF or typsin. Like the cell-rounding process, the cell-spreading process is temperature dependent, appears to be energy dependent, and is inhibited by cytochalasin B. Thus, EGF does not destroy the ability of the cell to spread; rather, in the presence of the EGF (or trypsin), cell spreading and the maintenance of the flattened state become dependent on external Ca(++). Because untreated cells remain flattened in the absence of Ca(++), the data suggest that EGF may disrupt Ca(++)-independent mechanisms of adhesion normally present in A-431 cells.
表皮生长因子（EGF）在无钙培养基中可诱导A - 431人表皮样癌细胞迅速变圆。多种其他多肽激素、细胞膜抗血清、局部麻醉剂、秋水仙碱、细胞松弛素B或环核苷酸均不能诱导细胞变圆。然而，胰蛋白酶与EGF一样，在无钙条件下可诱导A - 431细胞变圆。胰蛋白酶和EGF诱导的细胞变圆均依赖温度，似乎也依赖能量，且受到细胞松弛素的抑制，这表明微丝在细胞变圆过程中发挥了积极作用。然而，一项培养基转移实验表明，EGF诱导的细胞变圆并非由蛋白酶分泌所致，多种丝氨酸蛋白酶抑制剂对EGF诱导的细胞变圆过程也没有影响。细胞变圆并非归因于EGF对无钙培养基中钙离子释放的轻微刺激，因为离子载体A23187对钙离子释放的刺激既不诱导细胞变圆，也不阻断EGF诱导的细胞变圆。用EGF或胰蛋白酶处理后变圆的细胞，在向培养基中添加钙离子后会铺展，即使EGF或胰蛋白酶仍然存在。与细胞变圆过程一样，细胞铺展过程也依赖温度，似乎依赖能量，且受到细胞松弛素B的抑制。因此，EGF不会破坏细胞铺展的能力；相反，在EGF（或胰蛋白酶）存在时，并维持扁平状态变得依赖外部钙离子。由于未处理的细胞在无钙条件下保持扁平状态，这些数据表明，EGF可能破坏了A - 431细胞中正常存在的不依赖钙离子的黏附机制。
