RESUMO
There are a variety of bacterial defense strategies to survive in a hostile environment. Generation of extracellular polysaccharides has proved to be a simple but effective strategy against the host's innate immune system. A comparative genomics approach led us to identify a new protein family termed Stealth, most likely involved in the synthesis of extracellular polysaccharides. This protein family is characterized by a series of domains conserved across phylogeny from bacteria to eukaryotes. In bacteria, Stealth (previously characterized as SacB, XcbA, or WefC) is encoded by subsets of strains mainly colonizing multicellular organisms, with evidence for a protective effect against the host innate immune defense. More specifically, integrating all the available information about Stealth proteins in bacteria, we propose that Stealth is a D-hexose-1-phosphoryl transferase involved in the synthesis of polysaccharides. In the animal kingdom, Stealth is strongly conserved across evolution from social amoebas to simple and complex multicellular organisms, such as Dictyostelium discoideum, hydra, and human. Based on the occurrence of Stealth in most Eukaryotes and a subset of Prokaryotes together with its potential role in extracellular polysaccharide synthesis, we propose that metazoan Stealth functions to regulate the innate immune system. Moreover, there is good reason to speculate that the acquisition and spread of Stealth could be responsible for future epidemic outbreaks of infectious diseases caused by a large variety of eubacterial pathogens. Our in silico identification of a homologous protein in the human host will help to elucidate the causes of Stealth-dependent virulence. At a more basic level, the characterization of the molecular and cellular function of Stealth proteins may shed light on fundamental mechanisms of innate immune defense against microbial invasion.
Assuntos
Bactérias/imunologia , Bactérias/patogenicidade , Infecções Bacterianas/imunologia , Biologia Computacional , Proteínas/classificação , Proteínas/imunologia , Sequência de Aminoácidos , Animais , Bactérias/química , Bactérias/genética , Infecções Bacterianas/microbiologia , Sequência Conservada , Evolução Molecular , Genoma/genética , Humanos , Dados de Sequência Molecular , Filogenia , Proteínas/química , Proteínas/genética , Alinhamento de Sequência , Streptomyces coelicolor/genética , Fatores de VirulênciaRESUMO
The cell fate determinant Numb orchestrates tissue morphogenesis and patterning in developmental systems. In the human mammary gland, Numb is a tumor suppressor and regulates p53 levels. However, whether this function is linked to its role in fate determination remains unclear. Here, by exploiting an ex vivo system, we show that at mitosis of purified mammary stem cells (SCs), Numb ensures the asymmetric outcome of self-renewing divisions by partitioning into the progeny that retains the SC identity, where it sustains high p53 activity. Numb also controls progenitor maturation. At this level, Numb loss associates with the epithelial-to-mesenchymal transition and results in differentiation defects and reacquisition of stemness features. The mammary gland of Numb-knockout mice displays an expansion of the SC compartment, associated with morphological alterations and tumorigenicity in orthotopic transplants. This is because of low p53 levels and can be inhibited by restoration of Numb levels or p53 activity, which results in successful SC-targeted treatment.
Assuntos
Autorrenovação Celular , Células Epiteliais/fisiologia , Proteínas de Membrana/fisiologia , Proteínas do Tecido Nervoso/fisiologia , Proteína Supressora de Tumor p53/fisiologia , Animais , Carcinogênese , Células Cultivadas , Reprogramação Celular , Transição Epitelial-Mesenquimal , Feminino , Glândulas Mamárias Animais/citologia , Glândulas Mamárias Animais/metabolismo , Neoplasias Mamárias Animais/metabolismo , Neoplasias Mamárias Animais/patologia , Camundongos , Mitose , Morfogênese , Células-Tronco Neoplásicas/fisiologia , Transporte Proteico , Esferoides Celulares/metabolismoRESUMO
In the vast area of immunotherapies, the development of monoclonal antibodies as a therapeutic concept emerged as a quantum leap out of the area of traditional vaccines (Köhler and Milstein) in vitro selection and optimisation made it possible to elaborate a single biological molecule from the molecular plethora of an individual adaptive immune response and to utilize such a cloned antibody repeatedly in a generalized fashion whenever the therapeutic indication is given to humans. At present, some 25 therapeutic monoclonal antibodies are currently being marketed in oncology, exceeding sales of USD20bn in 2011. A total of about 270 antibodies are currently in Phase II and III clinical development. Working on the assumption of usually lower attrition rates for antibody candidates, we expect approximately 120 of these 270 antibodies to be finally approved. This poses some key questions. What level of differentiation is required so that the coming new antibody drugs can command premium pricing when members of the founding generation become generic and inexpensive? What will global demand for antibody drugs be in view of the rising buying power in emerging pharmaceutical ('pharmerging') markets, but which is still not comparable with that of developed ones? What would the next quantum leaps be that might potentially push antibody technology on to a next level by disruptive innovation? Presentations given at the Phacilitate Immunotherapy Leaders' Forum 2012 (9-11 May in Barcelona) reflected on these questions and provided some stimulating perspectives.
Assuntos
Anticorpos Monoclonais/economia , Imunoterapia/economia , Anticorpos Monoclonais/uso terapêutico , Congressos como Assunto , HumanosRESUMO
Canonical Wnt signaling plays a critical role in stem cell maintenance in epithelial homeostasis and carcinogenesis. Here, we show that in the mouse this role is critically mediated by Bcl9/Bcl9l, the mammalian homologues of Legless, which in Drosophila is required for Armadillo/beta-catenin signaling. Conditional ablation of Bcl9/Bcl9l in the intestinal epithelium, where the essential role of Wnt signaling in epithelial homeostasis and stem cell maintenance is well documented, resulted in decreased expression of intestinal stem cell markers and impaired regeneration of ulcerated colon epithelium. Adenocarcinomas with aberrant Wnt signaling arose with similar incidence in wild-type and mutant mice. However, transcriptional profiles were vastly different: Whereas wild-type tumors displayed characteristics of epithelial-mesenchymal transition (EMT) and stem cell-like properties, these properties were largely abrogated in mutant tumors. These findings reveal an essential role for Bcl9/Bcl9l in regulating a subset of Wnt target genes involved in controlling EMT and stem cell-related features and suggest that targeting the Bcl9/Bcl9l arm of Wnt signaling in Wnt-activated cancers might attenuate these traits, which are associated with tumor invasion, metastasis, and resistance to therapy.
Assuntos
Adenocarcinoma/patologia , Neoplasias do Colo/patologia , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Células-Tronco Neoplásicas/patologia , Proteínas Wnt/metabolismo , Adenocarcinoma/genética , Adenocarcinoma/metabolismo , Animais , Neoplasias do Colo/genética , Neoplasias do Colo/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/genética , Camundongos , Camundongos Transgênicos , Células-Tronco Neoplásicas/fisiologia , Fatores de Transcrição , Proteínas Wnt/biossíntese , Proteínas Wnt/genéticaRESUMO
The mammalian ortholog of the conserved Drosophila adaptor protein Numb (Nb) and its homolog Numblike (Nbl) modulate neuronal cell fate determination at least in part by antagonizing Notch signaling. Because the Notch pathway has been implicated in regulating hemopoietic stem cell self-renewal and T cell fate specification in mammals, we investigated the role of Nb and Nbl in hemopoiesis using conditional gene targeting. Surprisingly simultaneous deletion of both Nb and Nbl in murine bone marrow precursors did not affect the ability of stem cells to self-renew or to give rise to differentiated myeloid or lymphoid progeny, even under competitive conditions in mixed chimeras. Furthermore, T cell fate specification and intrathymic T cell development were unaffected in the combined absence of Nb and Nbl. Collectively our data indicate that the Nb family of adaptor proteins is dispensable for hemopoiesis and lymphopoiesis in mice, despite their proposed role in neuronal stem cell development.
Assuntos
Hematopoese/imunologia , Linfopoese/imunologia , Proteínas de Membrana/deficiência , Proteínas de Membrana/genética , Proteínas do Tecido Nervoso/deficiência , Proteínas do Tecido Nervoso/genética , Animais , Células da Medula Óssea/citologia , Células da Medula Óssea/metabolismo , Diferenciação Celular/genética , Diferenciação Celular/imunologia , Linhagem da Célula/genética , Linhagem da Célula/imunologia , Hematopoese/genética , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , Linfopoese/genética , Proteínas de Membrana/biossíntese , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Proteínas do Tecido Nervoso/biossíntese , Neurônios/citologia , Neurônios/metabolismo , Timo/citologia , Timo/metabolismoRESUMO
Notch is a key regulator of vertebrate neurogenesis and the cytoplasmic adaptor protein Numb is a modulator of the Notch signaling pathway. To address the role of murine Numb in development of the central nervous system, we used a conditional gene ablation approach. We show that Numb is involved in the maturation of cerebellar granule cells. Although the specification of neural cell fates in the cerebellum is not affected in the absence of Numb, the transition from a mitotic progenitor to a mature granule cell is aberrant and migration of postmitotic granule cells to the internal granule cell layer is delayed. In some animals, this results in a complete agenesis of granule cells and a strong ataxia. We confirmed these findings in vitro and found that Numb-deficient cerebellar progenitor cells show a marked delay in granule cell maturation. Our results suggest that Numb plays a role in the transition of a mitotic progenitor to a fully differentiated granule cell in the cerebellum. In addition, the maturation of Purkinje cells is also delayed in Numb-deficient mice.