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 spontaneous y 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.
Liu, S. Q. J., & Golan, D. E. (1999). T-cell stimulation through the T-cell receptor/CD3 complex regulates CD2 lateral mobility by a calcium/calmodulin-dependent mechanism. Biophysical Journal, 76(3), 1679–1692. https://doi.org/10.1016/S0006-3495(99)77327-3