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CLC chloride/proton exchangers may support acidification of endolysosomes and raise their luminal Cl - concentration. Disruption of endosomal ClC-3 causes severe neurodegeneration. To assess the importance of ClC-3 Cl - /H + exchange, we now generate Clcn3 unc/unc mice in which ClC-3 is converted into a Cl - channel. Unlike Clcn3 -/- mice, Clcn3 unc/unc mice appear normal owing to compensation by ClC-4 with which ClC-3 forms heteromers. ClC-4 protein levels are strongly reduced in Clcn3 -/- , but not in Clcn3 unc/unc mice because ClC-3 unc binds and stabilizes ClC-4 like wild-type ClC-3. Although mice lacking ClC-4 appear healthy, its absence in Clcn3 unc/unc /Clcn4 -/- mice entails even stronger neurodegeneration than observed in Clcn3 -/- mice. A fraction of ClC-3 is found on synaptic vesicles, but miniature postsynaptic currents and synaptic vesicle acidification are not affected in Clcn3 unc/unc or Clcn3 -/- mice before neurodegeneration sets in. Both, Cl - /H + -exchange activity and the stabilizing effect on ClC-4, are central to the biological function of ClC-3., (© 2020 The Authors. Published under the terms of the CC BY NC ND 4.0 license.)

Alzheimer's disease is characterized not only by extracellular amyloid plaques and neurofibrillary tangles, but also by microglia-mediated neuroinflammation. Recently, autophagy has been linked to the regulation of the inflammatory response. Thus, we investigated how an impairment of autophagy mediated by BECN1/Beclin1 reduction, as described in Alzheimer's disease patients, would influence cytokine production of microglia. Acutely stimulated microglia from Becn1 +/- mice exhibited increased expression of IL-1beta and IL-18 compared to wild-type microglia. Becn1 +/- APPPS1 mice also contained enhanced IL-1beta levels. The investigation of the IL-1beta/IL-18 processing pathway showed an elevated number of cells with inflammasomes and increased levels of NLRP3 and cleaved CASP1/Caspase1 in Becn1 +/- microglia. Super-resolation microscopy revealed a very close association of NLRP3 aggregates and LC3-positive vesicles. Interestingly, CALCOCO2 colocalized with NLRP3 and its downregulation increased IL-1beta release. These data support the notion that selective autophagy can impact microglia activation by modulating IL-1beta and IL-18 production via NLRP3 degradation and thus present a mechanism how impaired autophagy could contribute to neuroinflammation in Alzheimer's disease., (© 2019 The Authors.)