RESUMO
Grb7, a noncatalytic intracellular adaptor protein involved in cell migration, is overexpressed in certain invasive and metastatic solid tumors. We found a highly significant difference in the level of expression of Grb7 between chronic lymphocytic leukemia (CLL) cells obtained from stage I and stage IV patients (P<0.001). Using semiquantitative RT-PCR, we detected high levels of Grb7 in 88% of stage IV patients vs only 18% in stage I patients. A corresponding increase was found in the in vitro migration of stage IV CLL cells in comparison to stage I cells. The statistically significant difference in the expression of Grb7 between stage IV and stage I patients was preserved even when tested specifically in the ZAP70-positive group (P<0.01). These findings show that Grb7 levels reflect the severity of the disease, and may be used, in conjunction with ZAP70, to predict disease progression.
Assuntos
Movimento Celular , Leucemia Linfocítica Crônica de Células B/metabolismo , Proteínas/metabolismo , Estudos de Casos e Controles , Células Cultivadas , Doença , Progressão da Doença , Receptores ErbB/genética , Receptores ErbB/metabolismo , Proteína Adaptadora GRB7 , Humanos , Leucemia Linfocítica Crônica de Células B/patologia , Linfócitos/metabolismo , Linfócitos/patologia , Estadiamento de Neoplasias , Proteínas Tirosina Quinases/genética , Proteínas Tirosina Quinases/metabolismo , Proteínas/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteína-Tirosina Quinase ZAP-70RESUMO
In order to fully mature and participate in the humoral immune response, immature B cells must first migrate into specific areas in the spleen where they differentiate into mature cells. However, before their maturation in the spleen, immature B cells must be excluded from non-splenic secondary lymphoid organs where any antigen encounter would lead to the death of the cells because of the negative selection process. We have recently shown that immature B cells can actively exclude themselves from antigen-enriched sites by down-regulating their integrin-mediated adhesion in a process mediated by interferon-gamma (IFN-gamma). In this study, we followed the pathway by which IFN-gamma regulates the homing of B cells. We show here that the inhibitory signal of IFN-gamma is transmitted through the IFN-gamma receptor whose engagement leads to the activation of PI3K. This PI3K activation subsequently leads to the inhibition of PKCalpha phosphorylation and cytoskeleton rearrangement required for promoting integrin-mediated adhesion and migration of B cells.
Assuntos
Linfócitos B/metabolismo , Citoesqueleto/metabolismo , Regulação para Baixo , Interferon gama/biossíntese , Actinas/metabolismo , Animais , Linfócitos B/citologia , Western Blotting , Adesão Celular , Movimento Celular , Meios de Cultivo Condicionados/farmacologia , Inibidores Enzimáticos/farmacologia , Interferon gama/metabolismo , Isoenzimas/metabolismo , Camundongos , Fosfatidilinositol 3-Quinases/metabolismo , Fosforilação , Proteína Quinase C/metabolismo , Proteína Quinase C-alfa , Transdução de Sinais , Baço/citologia , Baço/metabolismo , Células Tumorais Cultivadas , Regulação para CimaRESUMO
The mechanism by which immature B cells are sequestered from encountering foreign antigens present in lymph nodes or sites of inflammation, before their final maturation in the spleen, has not been elucidated. We show here that immature B cells fail to home to the lymph nodes. These cells can actively exclude themselves from antigen-enriched sites by downregulating their integrin-mediated adhesion to the extracellular matrix protein, fibronectin. This inhibition is mediated by interferon gamma secretion. Perturbation of interferon gamma activity in vivo leads to the homing of immature B cells to the lymph nodes. This is the first example of autocrine regulation of immune cell migration to sites of foreign antigen presentation.
