Cell biology: Receptors for selective recycling.

This is the author accepted manuscript. The final version is available from Nature at http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14532.html

Autophagy Induction Rescues Toxicity Mediated by Proteasome Inhibition

The ubiquitin-proteasome and macroautophagy-lysosome pathways are major routes for intracytosolic protein degradation. In many systems, proteasome inhibition is toxic. A Nature article by Pandey et al. shows that this toxicity can be modulated by altering autophagic activity. Their tantalizing results suggest that overexpression of HDAC6 may increase flux through the autophagy pathway, thereby attenuating the toxicity resulting from proteasome inhibition

Mirror image phosphoinositides regulate autophagy.

Autophagosome formation is stimulated by canonical VPS34-dependent formation of phosphatidylinositol 3-phosphate [PI(3)P], which recruits effectors such as WIPI2. However, non-canonical VPS34-independent autophagy has also been proposed. We recently described that PI(5)P regulates autophagosome biogenesis, recruits WIPI2, and rescues autophagy in VPS34-inactivated cells. These alternative autophagy-initiating pathways reveal new druggable targets for treating neurodegeneration and cancer.We are grateful for funding from a Wellcome Trust Principal Research Fellowship (DCR) (095317/Z/11/Z), a Wellcome Trust Strategic Award (100140/Z/12/Z), The NIHR Biomedical Research Centre in Dementia at Addenbrooke’s Hospital, and an MRC Confidence in Concepts grant (DCR) for funding.This is the final version of the article. It first appeared from Taylor & Francis via http://dx.doi.org/10.1080/23723556.2015.101997

A location, location, location mutation impairs DNM2-mediated release of nascent autophagosomes from recycling endosomes.

Elucidation of the membranes contributing to autophagosomes has been a critical question in the field, and an area of active research. Recently, we showed that key events in autophagosome formation, from PtdIns3P formation/WIPI2 recruitment to LC3-GABARAP membrane conjugation, occur on the RAB11A-positive compartment (recycling endosomes). This observation raised the question of how the LC3-positive autophagosome precursors detach from the recycling endosome. We recently observed that DNM2 (dynamin 2) mediates this step, and described how the DNM2R465W mutation that causes centronuclear myopathy (CNM) leads to the accumulation of autophagic structures on recycling endosomes, thereby stalling macroautophagy/autophagy. This physiologically important step highlights the importance of understanding release of nascent autophagosomes from the recycling endosomes as part of the autophagy itinerary

Macroautophagy without LC3 conjugation?

A recent study makes the surprising observation that autophagosomes can still form in the absence of the core conjugation machinery. Furthermore, while such autophagosomes can fuse with lysosomes, their degradation is delayed, and this is associated with delayed destruction of the inner autophagosomal double membrane, highlighting a new role for proteins thought to act exclusively in the formation of autophagosomes in late stages of the autophagic itinerary within autolysosomes

Autophagy in Neuronal Development and Plasticity.

Autophagy is a highly conserved intracellular clearance pathway in which cytoplasmic contents are trafficked to the lysosome for degradation. Within neurons, it helps to remove damaged organelles and misfolded or aggregated proteins and has therefore been the subject of intense research in relation to neurodegenerative disease. However, far less is understood about the role of autophagy in other aspects of neuronal physiology. Here we review the literature on the role of autophagy in maintaining neuronal stem cells and in neuronal plasticity in adult life and we discuss how these contribute to structural and functional deficits observed in a range of human disorders

Over-expression of BCL2 rescues muscle weakness in a mouse model of oculopharyngeal muscular dystrophy

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset muscular dystrophy caused by a polyalanine expansion mutation in the coding region of the poly-(A) binding protein nuclear 1 (PABPN1) gene. In unaffected individuals, (GCG)6 encodes the first 6 alanines in a homopolymeric stretch of 10 alanines. In most patients, this (GCG)6 repeat is expanded to (GCG)8–13, leading to a stretch of 12–17 alanines in mutant PABPN1, which is thought to confer a toxic gain of function. Thus, OPMD has been modelled by expressing mutant PABPN1 transgenes in the presence of endogenous copies of the gene in cells and mice. In these models, increased apoptosis is seen, but it is unclear whether this process mediates OPMD. The role of apoptosis in the pathogenesis of different muscular dystrophies is unclear. Blocking apoptosis ameliorates muscle disease in some mouse models of muscular dystrophy such as laminin α-2-deficient mice, but not in others such as dystrophin-deficient (mdx) mice. Here we demonstrate that apoptosis is not only involved in the pathology of OPMD but also is a major contributor to the muscle weakness and dysfunction in this disease. Genetically blocking apoptosis by over-expressing BCL2 ameliorates muscle weakness in our mouse model of OPMD (A17 mice). The effect of BCL2 co-expression on muscle weakness is transient, since muscle weakness is apparent in mice expressing both A17 and BCL2 transgenes at late time points. Thus, while apoptosis is a major pathway that causes muscle weakness in OPMD, other cell death pathways may also contribute to the disease when apoptosis is inhibited

Autophagy as a promoter of longevity: insights from model organisms.

Autophagy is a conserved process that catabolizes intracellular components to maintain energy homeostasis and to protect cells against stress. Autophagy has crucial roles during development and disease, and evidence accumulated over the past decade indicates that autophagy also has a direct role in modulating ageing. In particular, elegant studies using yeasts, worms, flies and mice have demonstrated a broad requirement for autophagy-related genes in the lifespan extension observed in a number of conserved longevity paradigms. Moreover, several new and interesting concepts relevant to autophagy and its role in modulating longevity have emerged. First, select tissues may require or benefit from autophagy activation in longevity paradigms, as tissue-specific overexpression of single autophagy genes is sufficient to extend lifespan. Second, selective types of autophagy may be crucial for longevity by specifically targeting dysfunctional cellular components and preventing their accumulation. And third, autophagy can influence organismal health and ageing even non-cell autonomously, and thus, autophagy stimulation in select tissues can have beneficial, systemic effects on lifespan. Understanding these mechanisms will be important for the development of approaches to improve human healthspan that are based on the modulation of autophagy

Methods to analyze SNARE-dependent vesicular fusion events that regulate autophagosome biogenesis.

Autophagy is an important catabolic pathway that preserves cellular homeostasis. The formation of autophagosomes is a complex process requiring the reorganization of membranes from different compartments. Here we describe methods to analyze SNARE-dependent vesicular fusion events involving the homotypic and heterotypic fusion of autophagosome precursor structures. These two steps are essential for the maturation of small single-membrane autophagic precursors containing ATG16L1 and mATG9 proteins into double-membrane autophagosomes. The techniques described in this review are mostly based on live cell imaging, microscopy, and biochemistry using an in vitro fusion assay, and should help researchers to study autophagosome biogenesis.We are grateful to the Wellcome Trust (Principal Research Fellowship to DCR), a Wellcome Trust/MRC Strategic award in neurodegeneration, and a Wellcome Trust Strategic Grant to Cambridge Institute for Medical Research for funding.This is the final version. It was first published by Elsevier at http://www.sciencedirect.com/science/article/pii/S104620231400365

IFNB/interferon-β regulates autophagy via a MIR1-TBC1D15-RAB7 pathway.

Loss of IFNB/interferon-β in mice causes a Parkinson disease-like phenotype where many features, including SNCA/α-synuclein and MAPT/tau accumulation, can be attributed to a late-stage block in autophagic flux. Recently, we identified a mechanism that can explain this phenotype. We found that IFNB induces expression of Mir1, a microRNA that can reduce the levels of TBC1D15, a RAB GTPase-activating protein. Induction of this pathway decreases RAB7 activity and thereby stimulates macroautophagy/autophagy. The relevance of these key players is deeply conserved from humans to Caenorhabditis elegans, highlighting the importance of this ancient autophagy regulatory pathway.UK Dementia Research Institute at the University of Cambridge (funded by the MRC, Alzheimer’s Research UK and the Alzheimer’s Society), the National Institute for Health Research Cambridge Biomedical Research Centre, the Wellcome Trust (095317/Z/11/Z), the Spoelberch Foundation and an anonymous donation to the Cambridge Centre for Parkinson-Plus to D.C.R., NHMRC (Senior Research Fellowship GNT1137645 and Project Grant GNT1156481 to R.P.), veski Innovation Fellowship (VIF23 to R.P.), The Danish Council for Independent Research (DFF - 6110-00461 to P.E.), Lundbeck Foundation (R210-2015-3372 to P.E.), and Parkinsonforening in Denmark (to P.E.)