The CD3ε proline-rich sequence, and its interaction with Nck, is not required for T cell development and function

The CD3 epsilon proline-rich sequence (PRS) binds to the cytosolic adaptor molecule Nck after TCR ligation. It has been proposed that this interaction is essential for immunological synapse formation and T cell activation. To assess the physiological importance of the CM3 epsilon PRS, we have generated mice that lack this motif (CD3 epsilon.PRSM). Pull-down experiments demonstrated the inability of Nck to bind to the CD3 epsilon PRS in thymocytes from mutant mice after TCR ligation. Surprisingly, no differences were observed in the number and percentage of T cell subsets in the thymus and spleen, and there was no apparent defect in positive or negative selection. Furthermore, the proliferative response of CD3 epsilon.PRSM T cells to staphylococcal enterotoxin B and anti-CD3 Ab was normal. TCR surface expression, constitutive internalization, and Ag-induced down-modulation were also normal. These data suggest that the interaction between the CD3 epsilon PRS and Nck, or any other Src homology 3 domain-containing molecule, is not essential for T cell development and function.