Cai Y C, Cefai D, Schneider H, Raab M, Nabavi N, Rudd C E
Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.
Immunity. 1995 Oct;3(4):417-26. doi: 10.1016/1074-7613(95)90171-x.
CD28 costimulatory signals are required for lymphokine production and T cell proliferation. CD28 signaling recruits the intracellular proteins PI 3-kinase, ITK, and GRB-2/SOS. PI 3-kinase and GRB-2/SOS bind the CD28 cytoplasmic pYMNM motif via SH2 domains. We generated CD28 pYMNM mutants and found that Y191 mutation (Y191CD28F) disrupted both PI 3-kinase and GRB-2 binding, while M194 mutation (M194CD28C) disrupted only PI 3-kinase binding. Both mutants still bound ITK. We have assessed the ability of these selective mutants to support IL-2 production upon TCR zeta/CD3 ligation in the presence of CHO-CD86 (B7-2) cells. Both Y191CD28F and M194CD28C mutants failed to generate IL-2. These data directly implicate PI 3-kinase in CD28-mediated costimulation leading to IL-2 secretion. Wortmannin, an inhibitor of PI 3-kinase, induced cell apoptosis and as such was unsuitable for use in this study.
CD28共刺激信号是淋巴细胞因子产生和T细胞增殖所必需的。CD28信号传导招募细胞内蛋白PI 3激酶、ITK和GRB-2/SOS。PI 3激酶和GRB-2/SOS通过SH2结构域结合CD28细胞质pYMNM基序。我们构建了CD28 pYMNM突变体，发现Y191突变（Y191CD28F）破坏了PI 3激酶和GRB-2的结合，而M194突变（M194CD28C）仅破坏了PI 3激酶的结合。两种突变体仍能结合ITK。我们评估了这些选择性突变体在CHO-CD86（B7-2）细胞存在的情况下，TCR ζ/CD3连接时支持IL-2产生的能力。Y191CD28F和M194CD28C突变体均未能产生IL-2。这些数据直接表明PI 3激酶参与了CD28介导的共刺激，导致IL-2分泌。渥曼青霉素是一种PI 3激酶抑制剂，可诱导细胞凋亡，因此不适合用于本研究。
