Csk is a tyrosine kinase that phosphorylates the negative regulatory C-terminal tyrosine residue Y505 of Lck to maintain Lck in an inactive state. In resting T cells, Csk is targeted to lipid rafts through engagement of its SH2 domain with phosphotyrosine residue pY317 of PAG. PAG is expressed as a tyrosine phosphorylated protein in nonstimulated T-cells. This interaction of Csk and PAG allows activation of Csk and inhibition of Lck. Given that PAG-1 T cell knock out show a weak phenotype, some other protein may substitute in activating Csk.
Tuosto, L, Marinari, B, Piccolella, E, Simeoni, L, Schraven, B
Shevchenko, A, Korinek, V, Bruyns, E, Scherer, J, Hilgert, I, Brdicka, T, Cerny, J, Horejsi, V, Kornacker, B, Leo, A, Angelisova, P, Pavlistova, D, Schraven, B, Drbal, K, Kuramitsu, Y
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