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      TMEM175 deficiency impairs lysosomal and mitochondrial function and increases α-synuclein aggregation

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          Pancreatic cancers require autophagy for tumor growth.

          Macroautophagy (autophagy) is a regulated catabolic pathway to degrade cellular organelles and macromolecules. The role of autophagy in cancer is complex and may differ depending on tumor type or context. Here we show that pancreatic cancers have a distinct dependence on autophagy. Pancreatic cancer primary tumors and cell lines show elevated autophagy under basal conditions. Genetic or pharmacologic inhibition of autophagy leads to increased reactive oxygen species, elevated DNA damage, and a metabolic defect leading to decreased mitochondrial oxidative phosphorylation. Together, these ultimately result in significant growth suppression of pancreatic cancer cells in vitro. Most importantly, inhibition of autophagy by genetic means or chloroquine treatment leads to robust tumor regression and prolonged survival in pancreatic cancer xenografts and genetic mouse models. These results suggest that, unlike in other cancers where autophagy inhibition may synergize with chemotherapy or targeted agents by preventing the up-regulation of autophagy as a reactive survival mechanism, autophagy is actually required for tumorigenic growth of pancreatic cancers de novo, and drugs that inactivate this process may have a unique clinical utility in treating pancreatic cancers and other malignancies with a similar dependence on autophagy. As chloroquine and its derivatives are potent inhibitors of autophagy and have been used safely in human patients for decades for a variety of purposes, these results are immediately translatable to the treatment of pancreatic cancer patients, and provide a much needed, novel vantage point of attack.
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            Lysosomal physiology.

            Lysosomes are acidic compartments filled with more than 60 different types of hydrolases. They mediate the degradation of extracellular particles from endocytosis and of intracellular components from autophagy. The digested products are transported out of the lysosome via specific catabolite exporters or via vesicular membrane trafficking. Lysosomes also contain more than 50 membrane proteins and are equipped with the machinery to sense nutrient availability, which determines the distribution, number, size, and activity of lysosomes to control the specificity of cargo flux and timing (the initiation and termination) of degradation. Defects in degradation, export, or trafficking result in lysosomal dysfunction and lysosomal storage diseases (LSDs). Lysosomal channels and transporters mediate ion flux across perimeter membranes to regulate lysosomal ion homeostasis, membrane potential, catabolite export, membrane trafficking, and nutrient sensing. Dysregulation of lysosomal channels underlies the pathogenesis of many LSDs and possibly that of metabolic and common neurodegenerative diseases.
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              Addition of exogenous α-synuclein preformed fibrils to primary neuronal cultures to seed recruitment of endogenous α-synuclein to Lewy body and Lewy neurite-like aggregates.

              This protocol describes a primary neuronal model of formation of α-synuclein (α-syn) aggregates that recapitulate features of the Lewy bodies and Lewy neurites found in Parkinson's disease brains and other synucleinopathies. This model allows investigation of aggregate formation, their impact on neuron function, and development of therapeutics. Addition of preformed fibrils (PFFs) synthesized from recombinant α-syn to neurons seeds the recruitment of endogenous α-syn into aggregates characterized by detergent insolubility and hyperphosphorylation. Aggregate formation follows a lag phase of 2-3 d, followed by formation in axons by days 4-7, spread to somatodendritic compartments by days 7-10 and neuron death ~14 d after PFF addition. Here we provide methods and highlight the crucial steps for PFF formation, PFF addition to cultured hippocampal neurons and confirmation of aggregate formation. Neurons derived from various brain regions from nontransgenic and genetically engineered mice and rats can be used, allowing interrogation of the effect of specific genes on aggregate formation.
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                Author and article information

                Journal
                Proceedings of the National Academy of Sciences
                Proc Natl Acad Sci USA
                Proceedings of the National Academy of Sciences
                0027-8424
                1091-6490
                February 28 2017
                February 28 2017
                : 114
                : 9
                : 2389-2394
                Article
                10.1073/pnas.1616332114
                5338534
                28193887
                3c457553-1c66-4ad3-b50a-a75d47627c56
                © 2017
                History

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