RESUMO
To identify genes involved in signal transduction pathways that regulate T cell activation and development, murine fetal thymocytes were screened for expression of protein tyrosine kinase family members by the polymerase chain reaction. Using this approach, a non-receptor protein tyrosine kinase, txk, was identified and cloned. Tsk is expressed in thymocytes as early as fetal day 13.5 and its expression at the mRNA level continues throughout development. Txk transcripts are present in thymocytes, peripheral T cells and mast cell lines, but are not detectable in B cell macrophage/monocyte cell lines or in non-hematopoietic fetal or adult tissues. In both thymocytes and T cells, txk transcripts are down-regulated after activation with PMA and ionomycin, concanavalin A or T cell receptor cross-linking. Sequence analysis indicates that txk contains SH2, SH3 and kinase catalytic domains and belongs to the tec family of cytoplasmic protein tyrosine kinases which includes tec, itk and btk. Its unique N-terminus contains a proline-rich region, but unlike the other tec family members, does not contain a pleckstrin homology domain. The restricted expression pattern of txk and its regulation by T cell activation make it an excellent candidate for involvement in signal transduction during thymocyte development.
Assuntos
Proteínas Tirosina Quinases/genética , Linfócitos T/imunologia , Sequência de Aminoácidos , Animais , Sequência de Bases , Northern Blotting , Antígenos CD4/efeitos dos fármacos , Antígenos CD4/fisiologia , Antígenos CD8/efeitos dos fármacos , Antígenos CD8/fisiologia , Linhagem Celular , Mapeamento Cromossômico , Clonagem Molecular , Sequência Conservada , Cruzamentos Genéticos , Primers do DNA , DNA Complementar/genética , Embrião de Mamíferos/citologia , Embrião de Mamíferos/fisiologia , Regulação da Expressão Gênica/imunologia , Humanos , Ionomicina/farmacologia , Ativação Linfocitária , Mastócitos/enzimologia , Mastócitos/fisiologia , Camundongos , Dados de Sequência Molecular , Ésteres de Forbol/farmacologia , Reação em Cadeia da Polimerase/métodos , Proteínas Tirosina Quinases/sangue , RNA/química , RNA/genética , RNA Mensageiro/análise , RNA Mensageiro/fisiologia , Homologia de Sequência de Aminoácidos , Linfócitos T/efeitos dos fármacos , Timo/embriologia , Timo/enzimologia , Timo/fisiologiaRESUMO
Reconstruction of both the anterior cruciate ligament and posterior cruciate ligament has become increasingly common in orthopaedic practice. Once the gold standard for graft choice, the bone-patellar tendon-bone autograft has lost favor because of complications associated with its use. Attention has turned to other graft sources that lack a bone plug on 1 or both sides, such as hamstring autograft, and allografts including quadriceps, Achilles, and tibialis anterior tendons. We have developed a technique for graft preparation that can be used for a wide range of graft choices that has been shown both to provide better protection of the graft from interference screw damage, and to increase sequential compression of the graft in the bony tunnel, enhancing pull-out strength.