Identification of a new mechanism for preserving lysosomal functional integrity upon oxidative stress

Abstract

is a secreted protein, uses canonical secretion pathways, and interacts with particular subdomains of plasma membrane. 1.2 ApoD endocytosis occurs in a Basigin-independent manner. 1.3 Astroglial ApoD traffics through clathrin and caveolin-dependent endocytic pathways, and concentrates prominently in the late endosomallysosomal compartment (LELC). 1.4 ApoD is transiently enriched in the LELC upon oxidative stress, and is subsequently transported to autophagosomes. 1.5 LELC is a "functional niche" for ApoD. Chapter 2: ApoD controls lysosomal functional integrity and stabilizes their pH. 2.1 ApoD identifies two pH domains in the astroglial lysosomal compartment with differential responses to oxidative stress. 2.2. Oxidative stress produces an increase of ApoD-positive lysosomes near the plasma membrane. 2.3 ApoD is targeted to the lysosomal compartment in an oxidative stressdependent manner, both in differentiated neurons and primary astrocytes. 2.4 ApoD has an active role in the oxidation-sensitive lysosomal subdomain of cells, including neurons and astrocytes. 2.5 ApoD expression and targeting to lysosomes prevent lysosomal permeabilization. Chapter 3: ApoD-enriched astroglial-derived extracellular vesicles mediate neuroprotection upon oxidative stress. 97 3.1 Glia-neuron communication in vitro. 3.2 Neurons uptake glial-derived EVs enriched in ApoD. 3.3 Isolation and characterization of ApoD in glial EVs: ApoD as a very specific marker of glial exosomes. 3.4 ApoD influences EV biogenesis. Chapter 4: In addition to cell survival, ApoD affects biological processes in which optimal lysosomal function is important for glial cells. 4.1 ApoD modifies the dynamics of myelin phagocytosis by astrocytes. 4.2 Stable presence of ApoD in the lysosome is required to rescue ApoD-KO hypersialylated glycocalyx in astrocytes. 4.3 ApoD is required for the process of myelin glycocalyx removal and adequate subcellular localization of lysosomal and membrane sialidases in Schwann cells. Chapter 5: Lysosomal ApoD function rescues cells from neurodegenerative diseases of different origins. 5.1 ApoD-related Lipocalins rescue of proteinopathic neurodegeneration requires autophagosome-lysosome fusion. 5.2 Apolipoprotein D-mediated regulation of lysosomal membrane integrity preserve lysosomal function and promotes cell survival in Niemann-Pick Type A disease.