title: Identification of CMS as a cytosolic adaptor of the human pTalpha chain involved in pre-TCR function.
abstract: The T-cell receptor beta (TCRbeta)/pre-TCRalpha (pTalpha) pre-TCR complex (pre-TCR) signals the expansion and differentiation of de-veloping thymocytes. Functional pro-perties of the pre-TCR rely on its unique pTalpha chain, which suggests the participation of specific intracellular adaptors. However, pTalpha-interacting molecules remain unknown. Here, we identified a polyproline-arginine sequence in the human pTalpha 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 physiologic relevance of this interaction, we found that 1 such adaptor, CMS, interacted in vivo with human pTalpha, 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 colocalized with internalized pTalpha in traffic to lysosomal degradation. Notably, deletion of the pTalpha CIN85/CMS-binding motif impaired pre-TCR-mediated Ca(2+) mobilization and NFAT transcriptional activity, and precluded activation induced by overexpression of a CMS-SH3 N-terminal mutant. These results provide the first molecular evidence for a pTalpha intracellular adaptor involved in pre-TCR function.
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain.
authors.forename: María N
authors.initials: MN
authors.lastname: Navarro
authors.forename: Gretel
authors.initials: G
authors.lastname: Nusspaumer
authors.forename: Patricia
authors.initials: P
authors.lastname: Fuentes
authors.forename: Sara
authors.initials: S
authors.lastname: González-García
authors.forename: Juan
authors.initials: J
authors.lastname: Alcain
authors.forename: María L
authors.initials: ML
authors.lastname: Toribio
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D020013:Calcium Signaling; D002460:Cell Line; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D046912:Multiprotein Complexes; D050778:NFATC Transcription Factors / Q000378:metabolism; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology; D014162:Transfection