Función de la cadena ptalpha en la regulación de la expresión en membrana y la señalización del complejo pre-tcr humano

• Autores: María de las Nieves Navarro Lobato
• Directores de la Tesis: María Luisa Toribio García (dir. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2006
• Idioma: español
• Tribunal Calificador de la Tesis: Francisco Sánchez Madrid (presid.), Miguel Angel Alonso Lebrero (secret.), Balbino Jose Alarcon Sanchez (voc.), Isabel Mérida (voc.), Jerónimo Bravo Sicilia (voc.)
• Materias:
  • Ciencias médicas
• Enlaces
  • Tesis en acceso abierto en: Biblos-e Archivo
• Resumen

  • SUMMARY The pre-TCR, composed by TCR chain paired with the invariant pre-TCR (pTalpha) chain and the CD3 subunits (epsilon, gamma, delta and zeta), is transiently expressed during T cell development at the beta-selection checkpoint. Surface expression of the pre-TCR signals the selection, expansion, TCRbeta allelic exclusion and further differentiation of developing pre-T cells, in a ligand independent manner. For a long time, the pTalpha chain has been considered just as a structural component of the pre-TCR, but previous results from our laboratory have suggested an important role of the intracellular domain of human pTalpha in the regulation of pre-TCR expression and function.

    In this study, we have approached at the molecular level the role that the human pTalpha chain plays in pre-TCR function, focussing on the specific properties of its cytoplasmic domain. Particularly, we investigated the contribution of the pTalpha cytoplasmic domain to two main physiological features: 1) the regulation of pre-TCR cell surface expression, and 2) the constitutive activation of the pre-TCR. We first analyzed the dynamics of the pre-TCR cell surface expression and down-modulation in pre-T cell. Using different experimental procedures, which include flow cytometry, confocal microscopy and biochemical techniques, we showed that surface pre-TCR complexes are continually and rapidly endocytosed and degraded in the absence of extracellular ligation but do not recycle back to the cell surface. Therefore, the human pre-TCR behaves constitutively as an activated TCR without any need for ligand binding. We demonstrated in this study that the cytoplasmic domain of the pTalpha chain is sufficient to confer constitutive internalization and degradation properties to the conventional TCR, thus supporting its functional relevance in normal pre-TCR turnover. In addition, we show that the equilibrium between internalization and reexpression of the pre-TCR is partially dependent on Src-kina