Acres R B, Conlon P J, Mochizuki D Y, Gallis B
J Biol Chem. 1986 Dec 5;261(34):16210-4.
A cell surface protein known as T4 (CD4, Leu3), Mr = 55,000, is expressed on the subset of human T lymphocytes which provides helper function for B cell and cytotoxic T cell activities. We show that T4 is constitutively phosphorylated and that phorbol myristate acetate (PMA) induces a rapid serine phosphorylation which is followed by a fast dephosphorylation. Within 5 min after PMA treatment, there is a 24% reduction of T4 on the cell surface, by 4 h the loss is nearly complete, and by 20 h T4 is re-expressed. Addition of antigen to a T4+ antigen-reactive T cell clone induces both phosphorylation and dephosphorylation with kinetics similar to that described for PMA. Antigen also causes reduction of cell surface T4, although to a lesser degree than stimulation with PMA. The rapid phosphorylation/dephosphorylation of T4 as well as its movement from the cell surface suggest that T4 functions as a receptor for an unknown ligand.
一种称为T4（CD4，Leu3）、分子量为55,000的细胞表面蛋白，在人类T淋巴细胞亚群上表达，该亚群为B细胞和细胞毒性T细胞的活性提供辅助功能。我们发现T4持续磷酸化，佛波醇肉豆蔻酸酯乙酸盐（PMA）诱导快速的丝氨酸磷酸化，随后是快速去磷酸化。PMA处理后5分钟内，细胞表面的T4减少24%，4小时后损失几乎完全，20小时后T4重新表达。将抗原添加到T4 + 抗原反应性T细胞克隆中会诱导磷酸化和去磷酸化，其动力学与PMA描述的相似。抗原也会导致细胞表面T4减少，尽管程度比PMA刺激小。T4的快速磷酸化/去磷酸化及其从细胞表面的移动表明T4作为一种未知配体的受体发挥作用。
