RESUMO
Ras GTPase-activating proteins (RasGAPs) inhibit signal transduction initiated through the Ras small GTP-binding protein. However, which members of the RasGAP family act as negative regulators of T cell responses is not completely understood. In this study, we investigated potential roles for the RasGAPs RASA1 and neurofibromin 1 (NF1) in T cells through the generation and analysis of T cell-specific RASA1 and NF1 double-deficient mice. In contrast to mice lacking either RasGAP alone in T cells, double-deficient mice developed T cell acute lymphoblastic leukemia/lymphoma, which originated at an early point in T cell development and was dependent on activating mutations in the Notch1 gene. These findings highlight RASA1 and NF1 as cotumor suppressors in the T cell lineage.
Assuntos
Neurofibromina 1/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Receptor Notch1/genética , Proteína p120 Ativadora de GTPase/genética , Animais , Deleção de Genes , Regulação da Expressão Gênica , Camundongos , Camundongos Knockout , Mutação , Neurofibromina 1/deficiência , Neurofibromina 1/imunologia , Leucemia-Linfoma Linfoblástico de Células Precursoras/imunologia , Leucemia-Linfoma Linfoblástico de Células Precursoras/mortalidade , Leucemia-Linfoma Linfoblástico de Células Precursoras/patologia , Receptor Notch1/imunologia , Transdução de Sinais , Baço/imunologia , Baço/patologia , Análise de Sobrevida , Linfócitos T/imunologia , Linfócitos T/patologia , Timo/imunologia , Timo/patologia , Fatores de Tempo , Proteína p120 Ativadora de GTPase/deficiência , Proteína p120 Ativadora de GTPase/imunologiaRESUMO
We examined the role of mitogen-activated protein kinase (p(44/42) MAPK) in ANG II-induced contraction of lower esophageal sphincter (LES) and internal anal sphincter (IAS) smooth muscles. Studies were performed in the isolated smooth muscles and cells (SMC). ANG II-induced changes in the levels of phosphorylation of different signal transduction and effector proteins were determined before and after selective inhibitors. ANG II-induced contraction of the rat LES and IAS SMC was inhibited by genistein, PD-98059 [a specific inhibitor of MAPK kinases (MEK 1/2)], herbimycin A (a pp60(c-src) inhibitor), and antibodies to pp60(c-src) and p(120) ras GTPase-activating protein (p(120) rasGAP). ANG II-induced contraction of the tonic smooth muscles was accompanied by an increase in tyrosine phosphorylation of p(120) rasGAP. These were attenuated by genistein but not by PD-98059. ANG II-induced increase in phosphorylations of p(44/42) MAPKs and caldesmon was attenuated by both genistein and PD-98059. We conclude that pp60(c-src) and p(44/42) MAPKs play an important role in ANG II-induced contraction of LES and IAS smooth muscles.
