Recruitment and activation of PLCγ1 in T cells: a new insight into old domains

Engagement of the T-cell antigen receptor leads to recruitment of phospholipase Cγ1 (PLCγ1) to the LAT-nucleated signaling complex and to PLCγ1 activation in a tyrosine phosphorylation-dependent manner. The mechanism of PLCγ1 recruitment and the role of PLCγ1 Src homology (SH) domains in this process remain incompletely understood. Using a combination of biochemical methods and real-time fluorescent imaging, we show here that the N-terminal SH2 domain of PLCγ1 is necessary but not sufficient for its recruitment. Either the SH3 or C-terminal SH2 domain of PLCγ1, with the participation of Vav1, c-Cbl and Slp76, are required to stabilize PLCγ1 recruitment. All three PLCγ1 SH domains are required for phosphorylation of PLCγ1 Y783, which is critical for enzyme activation. These novel findings entailed revision of the currently accepted model of PLCγ1 recruitment and activation in T lymphocytes