Kanner S B, Damle N K, Blake J, Aruffo A, Ledbetter J A
Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, WA 98121.
J Immunol. 1992 Apr 1;148(7):2023-9.
Activation of T cells through the TCR/CD3 receptor complex with either specific Ag or antibody results in tyrosine phosphorylation of intracellular protein substrates and phosphatidylinositol-phospholipase C (PLC) signaling, leading to the generation of PI breakdown products and the mobilization of intracellular calcium. Stimulation of the T cell surface receptor CD2 similarly propagates early signals through phosphatidylinositol-PLC activation. Previous reports have shown that CD3 activation leads to tyrosine phosphorylation of the PLC isozyme PLC gamma 1. In this report, we investigated the potential similarity between CD3-induced signaling through PLC gamma 1 and that induced by CD2. We show that stimulation of CD2 receptors on T cells caused tyrosine phosphorylation of PLC gamma 1. Cross-linking of CD2 with CD3 receptors augmented the phosphorylation of PLC gamma 1 on tyrosine, whereas ligation of the CD45 tyrosine phosphatase with CD2 receptors prevented PLC gamma 1 tyrosine phosphorylation. T cells stimulated by ligation of CD2 with its counter-receptor in the form of a soluble LFA-3/Ig fusion protein cross-linked on the cell surface, resulted in a low, but detectable level of PLC gamma 1 phosphorylation with prolonged kinetics, whereas that induced by cross-linking with anti-CD2 was stronger but transient. Co-ligation of LFA-3/Ig with suboptimal concentrations of anti-CD3 resulted in profound augmentation of PLC gamma 1 tyrosine phosphorylation, mobilization of intracellular calcium and T cell proliferation. To explore the relationship between CD3- and CD2-stimulated signaling, T cells were desensitized through 1 h incubation with anti-CD3. CD3 receptor modulation potently down-regulated CD2-induced PLC gamma 1 tyrosine phosphorylation and calcium mobilization. In contrast, PMA or ionomycin treatment did not alter CD2-stimulated tyrosine phosphorylation of PLC gamma 1, suggesting that tyrosine kinase inhibition by CD3 receptor modulation was not caused by signaling events downstream of PLC gamma 1. Taken together, these results support the hypothesis that CD2 provides a potent co-stimulatory signal for CD3-induced T cell activation that is associated with tyrosine kinase(s) and PLC gamma 1.
通过TCR/CD3受体复合物与特异性抗原或抗体激活T细胞，会导致细胞内蛋白质底物的酪氨酸磷酸化以及磷脂酰肌醇 - 磷脂酶C（PLC）信号传导，从而产生磷脂酰肌醇分解产物并动员细胞内钙。同样，刺激T细胞表面受体CD2也会通过磷脂酰肌醇 - PLC激活来传递早期信号。先前的报道表明，CD3激活会导致PLC同工酶PLCγ1的酪氨酸磷酸化。在本报告中，我们研究了通过PLCγ1的CD3诱导信号传导与CD2诱导信号传导之间的潜在相似性。我们发现，刺激T细胞上的CD2受体会导致PLCγ1的酪氨酸磷酸化。CD2与CD3受体交联增强了PLCγ1酪氨酸的磷酸化，而CD45酪氨酸磷酸酶与CD2受体连接则阻止了PLCγ1酪氨酸磷酸化。用可溶性LFA-3/Ig融合蛋白形式的反受体交联在细胞表面上连接CD2刺激的T细胞，导致PLCγ1磷酸化水平较低但可检测到，动力学延长，而抗CD2交联诱导的则更强但短暂。LFA-3/Ig与次优浓度的抗CD3共同连接导致PLCγ1酪氨酸磷酸化、细胞内钙动员和T细胞增殖显著增强。为了探索CD3和CD2刺激信号传导之间的关系，T细胞通过与抗CD3孵育1小时进行脱敏。CD3受体调节有效地下调了CD2诱导的PLCγ1酪氨酸磷酸化和钙动员。相反，佛波酯（PMA）或离子霉素处理并未改变CD2刺激的PLCγ1酪氨酸磷酸化，这表明CD3受体调节对酪氨酸激酶的抑制不是由PLCγ1下游的信号事件引起的。综上所述，这些结果支持以下假设：CD2为CD3诱导的T细胞激活提供了一个强大的共刺激信号，该信号与酪氨酸激酶和PLCγ1相关。
