Response Multilayered Control of T Cell Receptor Phosphorylation

2009); the catalytic activities of PTPs have been estimated to be 10to 1000-fold higher than that of tyrosine kinases (discussedby Fischer et al., 1991). Another contributing factor is the activity of inhibitory kinases such as Csk, which also constrain T cell activation (Schoenborn et al., 2009). Progress in understanding TCR triggering will require the teasing apart of these and other competing factors and the identification of those factors with the largest impact on net phosphorylation of the TCR. The effects of pervanadate on phosphorylation levels in resting T cells observed by ourselves (Figures S1B and S1C) and by others many years ago (e.g., O’Shea et al., 1992) suggest that PTPs could be key. For us, the sheer weight of the numbers also warrants their serious consideration.