RESUMO
Linker for activation of T cells (LAT) is a scaffolding adaptor protein that is critical for T cell development and function. A mutation of LAT (Y136F) that disrupts phospholipase C-gamma1 activation and subsequent calcium influx causes a partial block in T cell development and leads to a severe lymphoproliferative disease in homozygous knock-in mice. One possible contribution to the fatal disease of LAT Y136F knock-in mice could be from autoreactive T cells generated in these mice because of altered thymocyte selection. To examine the impact of the LAT Y136F mutation on thymocyte positive and negative selection, we bred this mutation onto the HY T cell receptor (TCR) transgenic, recombination activating gene-2 knockout background. Female mice with this genotype showed a severe defect in positive selection, whereas male mice exhibited a phenotype resembling positive selection (i.e., development and survival of CD8(hi) HY TCR-specific T cells) instead of negative selection. These results support the hypothesis that in non-TCR transgenic, LAT Y136F knock-in mice, altered thymocyte selection leads to the survival and proliferation of autoreactive T cells that would otherwise be negatively selected in the thymus.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Transtornos Linfoproliferativos/genética , Proteínas de Membrana/genética , Proteínas Musculares/metabolismo , Mutação/genética , Fosfoproteínas/genética , Transdução de Sinais/imunologia , Linfócitos T/fisiologia , Timo/imunologia , Fosfolipases Tipo C/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Apoptose/imunologia , Sítios de Ligação/genética , Cálcio/metabolismo , Proliferação de Células , Primers do DNA , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Fosfolipase C gama , Fosfoproteínas/metabolismo , Receptores de Antígenos de Linfócitos T/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/genética , Linfócitos T/imunologia , Timo/citologiaRESUMO
Bam32 (B lymphocyte adapter molecule of 32 kDa) is an adapter protein expressed in some hematopoietic cells including B and T lymphocytes. It was previously shown that Bam32-deficient mice have defects in various aspects of B cell activation including B cell receptor (BCR)-induced Erk activation, BCR-induced proliferation and T-independent antibody responses. In this study, we have examined the role of Bam32 in T cell activation using Bam32-deficient mice. By comparing CD4(+) T cells from lymph nodes of wild-type and Bam32-deficient mice, we found that Bam32 was required for optimal TCR-induced Erk activation, cytokine production, proliferation and actin-mediated spreading of CD4(+) T cells. These results indicate a novel pathway to Erk activation in T cells involving the adapter protein Bam32.