RESUMO
PML-retinoic acid receptor alpha (RARalpha) regulated adaptor molecule 1 (PRAM-1) is an intracellular adaptor molecule that is upregulated during the induced granulocytic differentiation of promyelocytic leukemic cells and during normal human myelopoiesis. This report describes the generation of PRAM-1-deficient mice and an analysis of the function of this adaptor in neutrophil differentiation and mature neutrophil function. We demonstrate here that neutrophil differentiation is not impaired in PRAM-1-deficient mice and that PRAM-1-deficient neutrophils function normally following engagement of Fcgamma receptors. In contrast, mature PRAM-1-null neutrophils exhibit significant defects in adhesion-dependent reactive oxygen intermediate production and degranulation. Surprisingly, other integrin-dependent responses, such as cell spreading and activation of several signaling pathways, are normal. Together, these findings demonstrate the uncoupling of key integrin-dependent responses in the absence of PRAM-1 and show this adaptor to be critical for select integrin functions in neutrophils.
Assuntos
Integrinas/metabolismo , Neutrófilos/metabolismo , Proteínas/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Sequência de Aminoácidos , Animais , Cálcio/metabolismo , Degranulação Celular , Expressão Gênica , Marcação de Genes , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Dados de Sequência Molecular , Neutrófilos/citologia , Neutrófilos/imunologia , Proteínas Opsonizantes , Fagocitose , Testes de Precipitina , Estrutura Terciária de Proteína , Proteínas/química , Proteínas/genética , Explosão Respiratória/imunologia , Homologia de Sequência de Aminoácidos , Staphylococcus aureusRESUMO
While the contribution of intracellular adaptor proteins to lymphocyte activation has been well studied, the function of these molecules in innate immune effector cells such as neutrophils has not been extensively addressed. Here we demonstrate a critical role for the adaptor molecule SH2 domain-containing leukocyte-specific phosphoprotein of 76 kDa (SLP-76) in FcgammaR and integrin signaling. Stimulation of these receptors induces tyrosine phosphorylation and cytoplasmic relocalization of SLP-76 in freshly isolated murine neutrophils. Neutrophils lacking SLP-76 demonstrate decreased FcgammaR-induced calcium flux and reactive oxygen intermediate (ROI) production in response to immune complex stimulation. More dramatically, SLP-76-/- neutrophils fail to produce ROI, spread, or activate critical downstream regulators in response to integrin ligation. These results provide genetic evidence for a critical role of SLP-76 in the regulation of neutrophil function.