Longitudinal tracking of neuronal mitochondria delineates PINK1/Parkin-dependent mechanisms of mitochondrial recycling and degradation.

Altered mitochondrial quality control and dynamics may contribute to neurodegenerative diseases, including Parkinson's disease, but we understand little about these processes in neurons. We combined time-lapse microscopy and correlative light and electron microscopy to track individual mitochondria in neurons lacking the fission-promoting protein dynamin-related protein 1 (Drp1) and delineate the kinetics of PINK1-dependent pathways of mitochondrial quality control. Depolarized mitochondria recruit Parkin to the outer mitochondrial membrane, triggering autophagosome formation, rapid lysosomal fusion, and Parkin redistribution. Unexpectedly, these mitolysosomes are dynamic and persist for hours. Some are engulfed by healthy mitochondria, and others are deacidified before bursting. In other cases, Parkin is directly recruited to the matrix of polarized mitochondria. Loss of PINK1 blocks Parkin recruitment, causes LC3 accumulation within mitochondria, and exacerbates Drp1KO toxicity to dopamine neurons. These results define a distinct neuronal mitochondrial life cycle, revealing potential mechanisms of mitochondrial recycling and signaling relevant to neurodegeneration.

Potential Transfer of Polyglutamine and CAG-Repeat RNA in Extracellular Vesicles in Huntington's Disease: Background and Evaluation in Cell Culture.

In Huntington's disease (HD) the imperfect expanded CAG repeat in the first exon of the HTT gene leads to the generation of a polyglutamine (polyQ) protein, which has some neuronal toxicity, potentially mollified by formation of aggregates. Accumulated research, reviewed here, implicates both the polyQ protein and the expanded repeat RNA in causing toxicity leading to neurodegeneration in HD. Different theories have emerged as to how the neurodegeneration spreads throughout the brain, with one possibility being the transport of toxic protein and RNA in extracellular vesicles (EVs). Most cell types in the brain release EVs and these have been shown to contain neurodegenerative proteins in the case of prion protein and amyloid-beta peptide. In this study, we used a model culture system with an overexpression of HTT-exon 1 polyQ-GFP constructs in human 293T cells and found that the EVs did incorporate both the polyQ-GFP protein and expanded repeat RNA. Striatal mouse neural cells were able to take up these EVs with a consequent increase in the green fluorescent protein (GFP) and polyQ-GFP RNAs, but with no evidence of uptake of polyQ-GFP protein or any apparent toxicity, at least over a relatively short period of exposure. A differentiated striatal cell line expressing endogenous levels of Hdh mRNA containing the expanded repeat incorporated more of this mRNA into EVs as compared to similar cells expressing this mRNA with a normal repeat length. These findings support the potential of EVs to deliver toxic expanded trinucleotide repeat RNAs from one cell to another, but further work will be needed to evaluate potential EV and cell-type specificity of transfer and effects of long-term exposure. It seems likely that expanded HD-associated repeat RNA may appear in biofluids and may have use as biomarkers of disease state and response to therapy.

Potential function for the Huntingtin protein as a scaffold for selective autophagy.

Although dominant gain-of-function triplet repeat expansions in the Huntingtin (HTT) gene are the underlying cause of Huntington disease (HD), understanding the normal functions of nonmutant HTT protein has remained a challenge. We report here findings that suggest that HTT plays a significant role in selective autophagy. Loss of HTT function in Drosophila disrupts starvation-induced autophagy in larvae and conditional knockout of HTT in the mouse CNS causes characteristic cellular hallmarks of disrupted autophagy, including an accumulation of striatal p62/SQSTM1 over time. We observe that specific domains of HTT have structural similarities to yeast Atg proteins that function in selective autophagy, and in particular that the C-terminal domain of HTT shares structural similarity to yeast Atg11, an autophagic scaffold protein. To explore possible functional similarity between HTT and Atg11, we investigated whether the C-terminal domain of HTT interacts with mammalian counterparts of yeast Atg11-interacting proteins. Strikingly, this domain of HTT coimmunoprecipitates with several key Atg11 interactors, including the Atg1/Unc-51-like autophagy activating kinase 1 kinase complex, autophagic receptor proteins, and mammalian Atg8 homologs. Mutation of a phylogenetically conserved WXXL domain in a C-terminal HTT fragment reduces coprecipitation with mammalian Atg8 homolog GABARAPL1, suggesting a direct interaction. Collectively, these data support a possible central role for HTT as an Atg11-like scaffold protein. These findings have relevance to both mechanisms of disease pathogenesis and to therapeutic intervention strategies that reduce levels of both mutant and normal HTT.

Proteostasis in striatal cells and selective neurodegeneration in Huntington's disease.

Selective neuronal loss is a hallmark of neurodegenerative diseases, including Huntington's disease (HD). Although mutant huntingtin, the protein responsible for HD, is expressed ubiquitously, a subpopulation of neurons in the striatum is the first to succumb. In this review, we examine evidence that protein quality control pathways, including the ubiquitin proteasome system, autophagy, and chaperones, are significantly altered in striatal neurons. These alterations may increase the susceptibility of striatal neurons to mutant huntingtin-mediated toxicity. This novel view of HD pathogenesis has profound therapeutic implications: protein homeostasis pathways in the striatum may be valuable targets for treating HD and other misfolded protein disorders.

Asistencia psicologica del niño con cancer: II / Psychological assistence of children with cancer: II

El presente trabajo es la puesta a punto de recursos asistenciales tendientes al tratamiento y prevención de disturbios psicológicos en pacientes niños con patologías malignas, sometidos a tratamientos de características traumáticas. Los objetivos son mejorar las condiciones asistenciales en tratamientos de alto riesgo psicológico para el paciente, su grupo familiar y para el equipo tratante. Una vez más se destaca la importancia del proceso diagnóstico y en especial de la comunicación diagnóstica al niño. Para refrendar este acerto se presenta un caso de amputación de Miembro Inferior por Osteosarcoma, analizando los resultados del test gráfico de Hamer (HIP)

Asistencia psicológica del niño con cáncer / Psychological assistence of children with cancer

El presente trabajo describe la organización asistencial del psicólogo en un Servicio de Hemato-Oncologia Pediátrica. La misma se realiza a través de las siguentes estategias asistenciales: 1. Grupo de reflexión de profesionales: su objetivo es la reflexión acerca de los obstáculos que presente la area. 2. Interconsulta del médico tratante con el psicólogo a fin de evaluar situaciones de riesgo. 3. Entrevista a padre durante la etapa incial der tratamiento o bien ante la apacrición de dificultades. 4. Entrevista a pacientes por solicitud de los mismos o por la presencia de síntomas psicológicos de sufrimiento. 5. Grupo de padres como estrtegia de seguimiento y control. 6. Psicoterapia. Los obstáculos que se encontraron en el desarrollo de la tarea son: la falta de un espacio físico adecuado y las resistencias de los padres como el médico para escuchar al niño. El trabajo demuestra que el niño es una persona capaz de participar en las decisiones acerca de su tratamiento y ésto influye significativametne en la eficacia del mismo