Phosphorylation of CD28

The interaction of CD28 with its ligands, B7-1 (CD80) and B7-2 (CD86) on antigen-presenting cells enhances a number of TCR-mediated responses like production of interleukins. CD28 mediated costimulation is dependent upon phosphorylation of tyrosine residue 191 of the CD28 cytoplasmic tail, present in a 'YMNM' motif. p56Lck and p59Fyn phosphorylate CD28 and the phosphorylated residue allows the recruitment of PI3K, growth factor receptor-bound protein 2 (GRB2) and Grb2-related adaptor downstream of SHC (GADS) via their src-homology region 2 (SH2) domains.

CD28与其配体B7-1（CD80）和B7-2（CD86）在抗原呈递细胞上的相互作用，增强了多种由TCR介导的应答，例如白介素的产生。CD28介导的共刺激依赖于CD28胞浆尾部的酪氨酸残基191的磷酸化，该残基存在于'YMNM'基序中。p56Lck和p59Fyn磷酸化CD28，磷酸化的残基使得PI3K、生长因子受体结合蛋白2（GRB2）及Grb2相关适配蛋白（GADS）下游通过其src同源区域2（SH2）域被招募。