A critical role for the cytoplasmic tail of pTα in T lymphocyte development

Signals that emanate from the pre-T cell receptor (pre-TCR) regulate multiple processes required for the development of the αβ T cell lineage. In contrast to the γδ TCR, the pre-TCR localizes cell-autonomously to membrane rafts, where it appears to signal in a constitutive and ligand-independent manner. We addressed here the role played by structural features specific to the cytoplasmic domain of the pre-TCRα chain (pTα). More specifically, we examined a COOH-terminal proline-rich sequence that might play a role in signal transduction and a juxtamembrane cysteine residue that could be a target for palmitoylation, thus allowing spontaneous raft localization. Expression of pTα mutants in transgenic mice, retrovirally transduced T cell precursors and cell lines showed that the pTα cytoplasmic tail, in particular the proline-rich domain, plays a crucial role in pre-TCR signaling and T cell development. In contrast, the pTα juxtamembrane cysteine appeared to be dispensable for pre-TCR function.