Liu S Q, Golan D E
Department of Biological Chemistry and Molecular Pharmacology, Boston, Massachusetts 02115 USA.
Biophys J. 1999 Mar;76(3):1679-92. doi: 10.1016/S0006-3495(99)77327-3.
T lymphocyte activation through the T cell receptor (TCR)/CD3 complex alters the avidity of the cell surface adhesion receptor CD2 for its ligand CD58. Based on the observations that activation-associated increases in intracellular [Ca2+] ([Ca2+]i) strengthen interactions between T cells and antigen-presenting cells, and that the lateral mobility of cell surface adhesion receptors is an important regulator of cellular adhesion strength, we postulated that [Ca2+]i controls CD2 lateral mobility at the T cell surface. Human Jurkat T leukemia cells were stimulated by antibody-mediated cross-linking of the TCR/CD3 complex. CD2 was labeled with a fluorescently conjugated monoclonal antibody. Quantitative fluorescence microscopy techniques were used to measure [Ca2+]i and CD2 lateral mobility. Cross-linking of the TCR/CD3 complex caused an immediate increase in [Ca2+]i and, 10-20 min later, a decrease in the fractional mobility of CD2 from the control value of 68 +/- 1% to 45 +/- 2% (mean +/- SEM). One to two hours after cell stimulation the fractional mobility spontaneously returned to the control level. Under these and other treatment conditions, the fraction of cells with significantly elevated [Ca2+]i was highly correlated with the fraction of cells manifesting significantly reduced CD2 mobility. Pretreatment of cells with a calmodulin inhibitor or a calmodulin-dependent kinase inhibitor prevented Ca2+-mediated CD2 immobilization, and pretreatment of cells with a calcineurin phosphatase inhibitor prevented the spontaneous reversal of CD2 immobilization. These data suggest that T cell activation through the TCR/CD3 complex controls CD2 lateral mobility by a Ca2+/calmodulin-dependent mechanism, and that this mechanism may involve regulated phosphorylation and dephosphorylation of CD2 or a closely associated protein.
通过T细胞受体（TCR）/CD3复合物激活T淋巴细胞会改变细胞表面黏附受体CD2对其配体CD58的亲和力。基于以下观察结果：激活相关的细胞内[Ca2+]（[Ca2+]i）升高会增强T细胞与抗原呈递细胞之间的相互作用，并且细胞表面黏附受体的侧向迁移是细胞黏附强度的重要调节因子，我们推测[Ca2+]i控制T细胞表面CD2的侧向迁移。通过抗体介导的TCR/CD3复合物交联刺激人Jurkat T白血病细胞。用荧光偶联的单克隆抗体标记CD2。使用定量荧光显微镜技术测量[Ca2+]i和CD2的侧向迁移。TCR/CD3复合物的交联导致[Ca2+]i立即增加，10 - 20分钟后，CD2的分数迁移率从对照值68±1%降至45±2%（平均值±标准误）。细胞刺激后1至2小时，分数迁移率自发恢复到对照水平。在这些和其他处理条件下，[Ca2+]i显著升高的细胞分数与CD2迁移率显著降低的细胞分数高度相关。用钙调蛋白抑制剂或钙调蛋白依赖性激酶抑制剂预处理细胞可防止Ca2+介导的CD2固定，用钙调神经磷酸酶抑制剂预处理细胞可防止CD2固定的自发逆转。这些数据表明，通过TCR/CD3复合物激活T细胞通过Ca2+/钙调蛋白依赖性机制控制CD2的侧向迁移，并且该机制可能涉及CD2或紧密相关蛋白的磷酸化和去磷酸化调节。
