Upon TCR-CTLA-4 complex formation, CTLA4 is tyrosine phosphorylated. Src family tyrosine kinases Fyn, Lyn, and Lck associate with CTLA-4 and phosphorylate both Y-165 and Y-182 that are mainly responsible for interaction with Fyn through its SH2 domain. Once tyrosine 165 is phosphorylated, PP2A is activated and disassociates from CTLA4; this correlates with T cell inactivation.
Nakaseko, C, Yamamoto, T, Miyatake, S, Umemori, H, Saito, T
Darlington, PJ, Vijayakrishnan, L, Madrenas, J, Baroja, ML, Collins, M, Ling, V, Carreno, BM, Chau, TA, Bettelli, E, Kuchroo, VK
protein tyrosine kinase activity of Src family tyrosine kinases (SFKs) [cytosol]
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