Submitted June 8, 2007
Accepted August 30, 2007
Identification of CMS as a cystolic adaptor of the human pT
chain involved in pre-TCR function
Maria N Navarro, Gretel Nusspaumer, Patricia Fuentes, Sara Gonzalez-Garcia, Juan Alcain, and Maria L. Toribio*
Centro de Biologia Molecular "Severo Ochoa", Consejo Superior de Investigaciones Cientificas, Universidad Autonoma de Madrid, Madrid, Spain
* Corresponding author; email: mtoribio{at}cbm.uam.es.
The TCR
/pT
pre-TCR complex signals the expansion and differentiation of developing thymocytes. Functional properties of the pre-TCR rely on its unique pT chain, which suggests the participation of specific intracellular adaptors. However, pT-interacting molecules remain unknown. Here, we identified a polyproline-arginine sequence in the human pT cytoplasmic tail that interacted in vitro with SH3 domains of the CIN85/CMS family of adaptors, and mediated the recruitment of multiprotein complexes involving all (CMS, CIN85 and CD2BP3) members. Supporting the physiological relevance of this interaction, we found that one of such adaptors, CMS, interacted in vivo with human pT, and its expression was selectively up-regulated during human thymopoiesis in pre-TCR-activated thymocytes. Upon activation, pre-TCR clustering was induced, and CMS and polymerized actin were simultaneously recruited to the pre-TCR activation site. CMS also associated via its C-terminal region to the actin cytoskeleton in the endocytic compartment, where it co-localized with internalized pT in traffic to lysosomal degradation. Notably, deletion of the pTCIN85/CMS-binding motif impaired pre-TCR-mediated Ca2+ mobilization and NFAT transcriptional activity, and precluded activation induced by over-expression of a CMS-SH3 N-terminal mutant. These results provide the first molecular evidence for a pT intracellular adaptor involved in pre-TCR function.
