RESUMO
Galectin-3 (Gal-3) is a ß-galactoside binding protein that controls cell-cell and cell-extracellular matrix interactions. In lymphoid organs, gal-3 inhibits B cell differentiation by mechanisms poorly understood. The B cell development is dependent on tissue organization and stromal cell signaling, including IL-7 and Notch pathways. Here, we investigate possible mechanisms that gal-3 interferes during B lymphocyte differentiation in the bone marrow (BM) and spleen. The BM of gal-3-deficient mice (Lgals3-/- mice) was evidenced by elevated numbers of B220+CD19+c-Kit+IL-7R+ progenitor B cells. In parallel, CD45- bone marrow stromal cells expressed high levels of mRNA IL-7, Notch ligands (Jagged-1 and Delta-like 4), and transcription factors (Hes-1, Hey-1, Hey-2 and Hey-L). The spleen of Lgals3-/- mice was hallmarked by marginal zone disorganization, high number of IgM+IgD+ B cells and CD138+ plasma cells, overexpression of Notch ligands (Jagged-1, Delta-like 1 and Delta-like 4) by stromal cells and Hey-1. Morever, IgM+IgD+ B cells and B220+CD138+ CXCR4+ plasmablasts were significantly increased in the BM and blood of Lgals3-/- mice. For the first time, we demonstrated that gal-3 inhibits Notch signaling activation in lymphoid organs regulating earlier and terminal events of B cell differentiation.
Assuntos
Diferenciação Celular/genética , Galectina 3/genética , Células Secretoras de Insulina/metabolismo , Receptores Notch/genética , Animais , Células da Medula Óssea/citologia , Células da Medula Óssea/metabolismo , Regulação da Expressão Gênica/genética , Células Secretoras de Insulina/citologia , Interleucina-7/genética , Ligantes , Camundongos , Transdução de Sinais/genética , Baço/crescimento & desenvolvimento , Baço/metabolismo , Células Estromais/citologia , Células Estromais/metabolismo , Estruturas Linfoides Terciárias/genética , Fatores de Transcrição/genéticaRESUMO
Arhgap21 is a member of the Rho GTPase activating protein (RhoGAP) family, which function as negative regulators of Rho GTPases. Arhgap21 has been implicated in adhesion and migration of cancer cells. However, the role of Arhgap21 has never been investigated in hematopoietic cells. Herein, we evaluated functional aspects of hematopoietic stem and progenitor cells (HSPC) using a haploinsufficient (Arhgap21+/-) mouse. Our results show that Arhgap21+/- mice have an increased frequency of phenotypic HSC, impaired ability to form progenitor colonies in vitro and decreased hematopoietic engraftment in vivo, along with a decrease in LSK cell frequency during serial bone marrow transplantation. Arhgap21+/- hematopoietic progenitor cells have impaired adhesion and enhanced mobilization of immature LSK and myeloid progenitors. Arhgap21+/- mice also exhibit reduced erythroid commitment and differentiation, which was recapitulated in human primary cells, in which knockdown of ARHGAP21 in CMP and MEP resulted in decreased erythroid commitment. Finally, we observed enhanced RhoC activity in the bone marrow cells of Arhgap21+/- mice, indicating that Arhgap21 functions in hematopoiesis may be at least partially mediated by RhoC inactivation.
Assuntos
Células da Medula Óssea/patologia , Proteínas Ativadoras de GTPase/fisiologia , Haploinsuficiência , Hematopoese/fisiologia , Células-Tronco Hematopoéticas/patologia , Proteína de Ligação a GTP rhoC/metabolismo , Animais , Células da Medula Óssea/metabolismo , Diferenciação Celular , Movimento Celular , Proliferação de Células , Células Cultivadas , Células Eritroides/metabolismo , Células Eritroides/patologia , Fibronectinas/metabolismo , Células-Tronco Hematopoéticas/metabolismo , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína de Ligação a GTP rhoC/genéticaRESUMO
The CATS (FAM64A) protein interacts with CALM (PICALM) and the leukemic fusion protein CALM/AF10. CATS is highly expressed in leukemia, lymphoma and tumor cell lines and its protein levels strongly correlates with cellular proliferation in both malignant and normal cells. In order to obtain further insight into CATS function we performed an extensive analysis of CATS expression during differentiation of leukemia cell lines. While CATS expression decreased during erythroid, megakaryocytic and monocytic differentiation, a markedly increase was observed in the ATRA induced granulocytic differentiation. Lentivirus mediated silencing of CATS in U937 cell line resulted in somewhat reduced proliferation, altered cell cycle progression and lower migratory ability in vitro; however was not sufficient to inhibit tumor growth in xenotransplant model. Of note, CATS knockdown resulted in reduced clonogenicity of CATS-silenced cells and reduced expression of the self-renewal gene, GLI-1. Moreover, retroviral mediated overexpression of the murine Cats in primary bone marrow cells lead to decreased colony formation. Although our in vitro data suggests that CATS play a role in cellular processes important for tumorigenesis, such as cell cycle control and clonogenicity, these effects were not observed in vivo.