RESUMEN
The ubiquitin-proteasome system (UPS) and macroautophagy (autophagy) are central to normal proteostasis and interdependent in that autophagy is known to compensate for the UPS to alleviate ensuing proteotoxic stress that impairs cell function. UPS and autophagy dysfunctions are believed to have a major role in the pathomechanisms of neurodegenerative disease. Here we show that continued 26S proteasome dysfunction in mouse brain cortical neurons causes paranuclear accumulation of fragmented dysfunctional mitochondria, associated with earlier recruitment of Parkin and lysine 48-linked ubiquitination of mitochondrial outer membrane (MOM) proteins, including Mitofusin-2. Early events also include phosphorylation of p62/SQSTM1 (p62) and increased optineurin, as well as autophagosomal LC3B and removal of some mitochondria, supporting the induction of selective autophagy. Inhibition of the degradation of ubiquitinated MOM proteins with continued 26S proteasome dysfunction at later stages may impede efficient mitophagy. However, continued 26S proteasome dysfunction also decreases the levels of essential autophagy proteins ATG9 and LC3B, which is characterised by decreases in their gene expression, ultimately leading to impaired autophagy. Intriguingly, serine 351 phosphorylation of p62 did not enhance its binding to Keap1 or stabilise the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor in this neuronal context. Nrf2 protein levels were markedly decreased despite transcriptional activation of the Nrf2 gene. Our study reveals novel insights into the interplay between the UPS and autophagy in neurons and is imperative to understanding neurodegenerative disease where long-term proteasome inhibition has been implicated.
Asunto(s)
Autofagia/genética , Proteína 1 Asociada A ECH Tipo Kelch/genética , Mitocondrias/genética , Mitofagia/genética , Factor 2 Relacionado con NF-E2/genética , Proteína Sequestosoma-1/genética , Animales , Proteínas de Ciclo Celular , Proteínas del Ojo/metabolismo , GTP Fosfohidrolasas/metabolismo , Humanos , Proteína 1 Asociada A ECH Tipo Kelch/metabolismo , Proteínas de Transporte de Membrana , Ratones , Mitocondrias/metabolismo , Mitocondrias/patología , Factor 2 Relacionado con NF-E2/metabolismo , Neuronas/metabolismo , Neuronas/patología , Fosforilación , Complejo de la Endopetidasa Proteasomal/genética , Proteína Sequestosoma-1/metabolismo , Ubiquitina , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
PURPOSE: Treatment of long-gap esophageal atresia challenges pediatric surgeons. Dr. Foker described utilization of external traction sutures to promote in-vivo growth through tension-induced lengthening, but reproducibility of this technique is difficult. We describe a safe and reproducible traction system using transduction of hydrostatic pressure as a surrogate for tension. METHODS: We conducted a multi-institutional review of patients treated with this system from 2005 to 2012. All children had sutures applied to both pouches with continuous measurement of associated hydrostatic pressures (tension). Main outcome measures were days to delayed primary repair and thoracotomies prior to primary repair. RESULTS: Seven children were included. Median time to delayed repair was 15 days (range: 6-47 days). Three patients required repeat thoracotomies owing to mechanical entrapment of a pouch, all identified early by this system. All required postoperative dilations. Three had self-limited postdilation leaks, and there was one operation-related leak. CONCLUSIONS: This system provides reproducible traction application, facilitating staged primary repair by preventing major failures through limiting excessive traction and guides re-exploration for trapped segments. Larger studies are needed to determine the optimal tension protocol, prevent postoperative leaks, while decreasing the need for dilations and time to enteral feeding.
Asunto(s)
Atresia Esofágica/cirugía , Esófago/cirugía , Cuidados Preoperatorios/métodos , Técnicas de Sutura , Tracción/métodos , Anastomosis Quirúrgica , Fuga Anastomótica , Fenómenos Biomecánicos , Femenino , Humanos , Presión Hidrostática , Lactante , Estimación de Kaplan-Meier , Masculino , Reproducibilidad de los Resultados , Estudios Retrospectivos , ToracotomíaRESUMEN
Laryngotracheoesophageal cleft (LTEC) is a rare congenital anomaly that results from failed posterior fusion of the cricoid cartilage and incomplete development of the tracheoesophageal septum. LTEC presents with increased secretions, respiratory distress, aspiration and recurrent pulmonary infections. The severity of presenting symptoms is dependent on the type of cleft. LTEC is most commonly classified into four types (I, II, III and IV) based on the inferior extent of the cleft. Types III and IV LTEC are associated with high morbidity and mortality and require timely diagnosis and repair for survival. Most patients who survive repair of Type IV LTEC have long-term tracheotomy dependency with minimal chance of decannulation. We report on a case of a long-term survivor of Type IV who has been safely decannulated.