RESUMEN
Spinal muscular atrophy (SMA) is a monogenic disorder caused by loss of function mutations in the survival motor neuron 1 gene, which results in a broad range of disease severity, from neonatal to adult onset. There is currently a concerted effort to define the natural history of the disease and develop outcome measures that accurately capture its complexity. As several therapeutic strategies are currently under investigation and both the FDA and EMA have recently approved the first medical treatment for SMA, there is a critical need to identify the right association of responsive outcome measures and biomarkers for individual patient follow-up. As an approved treatment becomes available, untreated patients will soon become rare, further intensifying the need for a rapid, prospective and longitudinal study of the natural history of SMA Type 2 and 3. Here we present the baseline assessments of 81 patients aged 2 to 30 years of which 19 are non-sitter SMA Type 2, 34 are sitter SMA Type 2, 9 non-ambulant SMA Type 3 and 19 ambulant SMA Type 3. Collecting these data at nine sites in France, Germany and Belgium established the feasibility of gathering consistent data from numerous and demanding assessments in a multicenter SMA study. Most assessments discriminated between the four groups well. This included the Motor Function Measure (MFM), pulmonary function testing, strength, electroneuromyography, muscle imaging and workspace volume. Additionally, all of the assessments showed good correlation with the MFM score. As the untreated patient population decreases, having reliable and valid multi-site data will be imperative for recruitment in clinical trials. The pending two-year study results will evaluate the sensitivity of the studied outcomes and biomarkers to disease progression. TRIAL REGISTRATION: ClinicalTrials.gov (NCT02391831).
Asunto(s)
Atrofias Musculares Espinales de la Infancia/epidemiología , Adolescente , Adulto , Niño , Preescolar , Femenino , Humanos , Estudios Longitudinales , Pulmón/fisiopatología , Masculino , Fuerza Muscular , Debilidad Muscular/complicaciones , Desempeño Psicomotor , Atrofias Musculares Espinales de la Infancia/complicaciones , Atrofias Musculares Espinales de la Infancia/fisiopatología , Adulto JovenRESUMEN
In addition to its well-known effect on migration and homing of hematopoietic stem/progenitor cells (HSPCs), CXCL12 chemokine also exhibits a cell cycle and survival-promoting factor for human CD34(+) HSPCs. CXCR4 was suggested to be responsible for CXCL12-induced biological effects until the recent discovery of its second receptor, CXCR7. Until now, the participation of CXCR7 in CXCL12-induced HSPC cycling and survival is unknown. We show here that CXCL12 was capable of binding CXCR7 despite its scarce expression at CD34(+) cell surface. Blocking CXCR7 inhibited CXCL12-induced Akt activation as well as the percentage of CD34(+) cells in cycle, colony formation, and survival, demonstrating its participation in CXCL12-induced functional effects in HSPCs. At steady state, CXCR7 and ß-arrestin2 co-localized near the plasma membrane of CD34(+) cells. After CXCL12 treatment, ß-arrestin2 translocated to the nucleus, and this required both CXCR7 and CXCR4. Silencing ß-arrestin expression decreased CXCL12-induced Akt activation in CD34(+) cells. Our results demonstrate for the first time the role of CXCR7, complementary to that played by CXCR4, in the control of HSPC cycling, survival, and colony formation induced by CXCL12. We also provide evidence for the involvement of ß-arrestins as signaling hubs downstream of both CXCL12 receptors in primary human HSPCs.
Asunto(s)
Arrestinas/metabolismo , Ciclo Celular , Quimiocina CXCL12/metabolismo , Células Madre Hematopoyéticas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Receptores CXCR/metabolismo , Antígenos CD34/metabolismo , Supervivencia Celular , Ensayo de Unidades Formadoras de Colonias , Activación Enzimática , Humanos , Espacio Intracelular/metabolismo , Fosforilación , Unión Proteica , Transporte de Proteínas , beta-ArrestinasRESUMEN
Several cytokines and growth factors are released by proteolytic cleavage of a membrane-anchored precursor, through the action of ADAM (a disintegrin and metalloprotease) metalloproteases. The activity of these proteases is regulated through largely unknown mechanisms. In this study we show that Ab engagement of several tetraspanins (CD9, CD81, CD82) increases epidermal growth factor and/or TNF-alpha secretion through a mechanism dependent on ADAM10. The effect of anti-tetraspanin mAb on TNF-alpha release is rapid, not relayed by intercellular signaling, and depends on an intact MEK/Erk1/2 pathway. It is also associated with a concentration of ADAM10 in tetraspanin-containing patches. We also show that a large fraction of ADAM10 associates with several tetraspanins, indicating that ADAM10 is a component of the "tetraspanin web." These data show that tetraspanins regulate the activity of ADAM10 toward several substrates, and illustrate how membrane compartmentalization by tetraspanins can control the function of cell surface proteins such as ectoproteases.
Asunto(s)
Proteínas ADAM/metabolismo , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Antígenos CD/metabolismo , Factor de Crecimiento Epidérmico/metabolismo , Proteína Kangai-1/metabolismo , Glicoproteínas de Membrana/metabolismo , Proteínas de la Membrana/metabolismo , Factor de Necrosis Tumoral alfa/metabolismo , Proteínas ADAM/inmunología , Proteína ADAM10 , Secretasas de la Proteína Precursora del Amiloide/inmunología , Anticuerpos Monoclonales/inmunología , Antígenos CD/inmunología , Western Blotting , Línea Celular Tumoral , Ensayo de Inmunoadsorción Enzimática , Factor de Crecimiento Epidérmico/inmunología , Citometría de Flujo , Técnica del Anticuerpo Fluorescente , Humanos , Inmunoprecipitación , Proteína Kangai-1/inmunología , Glicoproteínas de Membrana/inmunología , Proteínas de la Membrana/inmunología , Microscopía Confocal , Interferencia de ARN , Transducción de Señal/inmunología , Tetraspanina 28 , Tetraspanina 29 , Transfección , Factor de Necrosis Tumoral alfa/inmunologíaRESUMEN
Cell cycle regulation plays a fundamental role in stem cell biology. A balance between quiescence and proliferation of hematopoietic stem cells in interaction with the microenvironment is critical for sustaining long-term hematopoiesis and for protection against stress. We analyzed the molecular mechanisms by which stromal cell-derived factor-1 (SDF-1) exhibited a cell cycle-promoting effect and interacted with transforming growth factor-beta (TGF-beta), which has negative effects on cell cycle orchestration of human hematopoietic CD34(+) progenitor cells. We demonstrated that a low concentration of SDF-1 modulated the expression of key cell cycle regulators such as cyclins, cyclin-dependent kinase inhibitors, and TGF-beta target genes, confirming its cell cycle-promoting effect. We showed that a cross-talk between SDF-1- and TGF-beta-related signaling pathways involving phosphatidylinositol 3-kinase (PI3K)/Akt phosphorylation participated in the control of CD34(+) cell cycling. We demonstrated a pivotal role of two downstream effectors of the PI3K/Akt pathway, FoxO3a and mammalian target of rapamycin, as connectors in the SDF-1-/TGF-beta-induced control of the cycling/quiescence switch and proposed a model integrating a dialogue between the two molecules in cell cycle progression. Our data shed new light on the signaling pathways involved in SDF-1 cell cycle-promoting activity and suggest that the balance between SDF-1- and TGF-beta-activated pathways is critical for the regulation of hematopoietic progenitor cell cycle status.