RESUMO
CD44 is a multistructural and multifunctional glycoprotein, the diversity of which is generated by alternative splicing. In this communication we review some aspects related to CD44 structure and function in experimental autoimmune inflammation, focusing on research performed in our own laboratory. We have found that CD44 targeting by antibody, passively injected into DBA/1 mice with collagen-induced arthritis (CIA) and NOD mice with type I diabetes or actively generated by CD44 cDNA vaccination of SJL/j mice with autoimmune encephalomyelitis, markedly reduced the pathological manifestations of these diseases by attenuating cell migration of the inflammatory cells and/or by their apoptotic killing. However, genetic deletion of CD44 by knockout technology enhanced the development of CIA because of molecular redundancy mediated by RHAMM (a receptor of hyaluronan-mediated motility). The mechanisms that stand behind these findings are discussed.
Assuntos
Anticorpos/imunologia , Doenças Autoimunes/imunologia , Doenças Autoimunes/metabolismo , Receptores de Hialuronatos/imunologia , Receptores de Hialuronatos/metabolismo , Animais , Doenças Autoimunes/induzido quimicamente , Colágeno/farmacologia , Modelos Animais de Doenças , Humanos , Inflamação/induzido quimicamente , Inflamação/imunologia , Inflamação/metabolismo , Camundongos , Camundongos KnockoutRESUMO
Given the prevalence of Ras mutations in human cancer, it is critical to understand the effector pathways downstream of oncogenic Ras leading to transformation. To directly assess the requirement for Rac1 in K-ras-induced tumorigenesis, we employed a model of lung cancer in which an oncogenic allele of K-ras could be activated by Cre-mediated recombination in the presence or absence of conditional deletion of Rac1. We show that Rac1 function is required for tumorigenesis in this model. Furthermore, although Rac1 deletion alone was compatible with cell viability and proliferation, when combined with K-ras activation in primary epithelial cells, loss of Rac1 caused a profound reduction in proliferation. These data show a specific requirement for Rac1 function in cells expressing oncogenic K-ras.
Assuntos
Adenocarcinoma/genética , Adenoma/genética , Transformação Celular Neoplásica/genética , Genes ras/fisiologia , Neoplasias Pulmonares/genética , Neuropeptídeos/fisiologia , Proteínas rac de Ligação ao GTP/fisiologia , Adenocarcinoma/mortalidade , Adenocarcinoma/patologia , Adenoma/mortalidade , Adenoma/patologia , Animais , Células Cultivadas , Progressão da Doença , Neoplasias Pulmonares/mortalidade , Neoplasias Pulmonares/patologia , Camundongos , Camundongos Transgênicos , Proteínas rac1 de Ligação ao GTPRESUMO
Upon maturation, dendritic cells (DCs) acquire the unique ability to activate naïve T cells. We used time-lapse video microscopy and two-photon imaging of intact lymph nodes to show that after establishing initial contact between their dendrites and naïve T lymphocytes, mature DCs migrate toward the contacted lymphocytes. Subsequently, the DCs tightly entrap the T cells within a complex net of membrane extensions. The Rho family guanosine triphosphatases Rac1 and Rac2 but not Rho itself control the formation of dendrites in mature DCs, their polarized short-range migration toward T cells, and T cell priming.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Células Dendríticas/fisiologia , Ativação Linfocitária , Proteínas rac de Ligação ao GTP/metabolismo , Proteínas rac1 de Ligação ao GTP/metabolismo , Animais , Linfócitos T CD4-Positivos/fisiologia , Comunicação Celular , Polaridade Celular , Extensões da Superfície Celular/fisiologia , Extensões da Superfície Celular/ultraestrutura , Citoesqueleto/fisiologia , Células Dendríticas/imunologia , Células Dendríticas/ultraestrutura , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microscopia de Vídeo , Proteínas rac de Ligação ao GTP/antagonistas & inibidores , Proteínas rac de Ligação ao GTP/genética , Proteínas rac1 de Ligação ao GTP/antagonistas & inibidores , Proteínas rac1 de Ligação ao GTP/genética , Proteínas rho de Ligação ao GTP/antagonistas & inibidores , Proteínas rho de Ligação ao GTP/metabolismo , Proteína RAC2 de Ligação ao GTPRESUMO
Rac GTPases are activated by extracellular stimuli and contribute to cellular responses including cytoskeletal changes and cell migration. Dominant-negative Rac1 has been used to implicate Rac GTPases in these responses, but which of the three mammalian Rac isoforms it inhibits is not known. We show that mouse bone marrow-derived macrophages express Rac1, low levels of Rac2 but not Rac3. As Rac1-null mice die early in development, we have used mice with a loxP-flanked allele of Rac1 and the type I interferon-inducible Mx1-Cre transgene to address for the first time the specific role of Rac1 in cell motility. Bone marrow-derived macrophages isolated from mice treated with polyIC to induce interferon lack detectable Rac1, and there is no compensatory increase in Rac2 or Cdc42 expression. Rac1-deficient macrophages have an altered morphology: they are significantly more elongated than control cells and have a reduced adhesive area. Re-expression of Rac1 reverts the morphology to that of control cells. Loss of Rac1 reduces but does not completely prevent membrane ruffling in response to CSF-1. However, Rac1-deficient macrophages show normal migration and chemotaxis. Thus in macrophages Rac1 is primarily responsible for regulating cell morphology, contributes to membrane ruffling, but is not required for migration.
Assuntos
Proteínas rac1 de Ligação ao GTP/deficiência , Animais , Sequência de Bases , Adesão Celular/fisiologia , Membrana Celular/fisiologia , Movimento Celular/fisiologia , DNA Complementar/genética , Expressão Gênica , Técnicas In Vitro , Fator Estimulador de Colônias de Macrófagos/farmacologia , Macrófagos/citologia , Macrófagos/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Coativador 3 de Receptor Nuclear , Fenótipo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Proteínas rac de Ligação ao GTP/genética , Proteínas rac de Ligação ao GTP/metabolismo , Proteínas rac1 de Ligação ao GTP/genética , Proteínas rac1 de Ligação ao GTP/fisiologia , Proteína RAC2 de Ligação ao GTPRESUMO
The Rac1 guanosine triphosphatase (GTPase) has been implicated in multiple cellular functions, including actin dynamics, proliferation, apoptosis, adhesion, and migration resulting from signaling by multiple receptors, including the B cell antigen receptor (BCR). We used conditional gene targeting to generate mice with specific Rac1 deficiency in the B cell lineage. In the absence of both Rac1 and the highly related Rac2, B cell development was almost completely blocked. Both GTPases were required to transduce BCR signals leading to proliferation, survival and up-regulation of BAFF-R, a receptor for BAFF, a key survival molecule required for B cell development and maintenance.