Sex-dependent calcium hyperactivity due to lysosomal-related dysfunction in astrocytes from APOE4 versus APOE3 gene targeted replacement mice

Molecular Neurodegeneration

Eleanna Kara¹  Eloise Hudry¹  Candela González-Arias²  Gertrudis Perea²  Javier Vitorica³  Marta Martinez-Vicente³  Antonia Gutiérrez⁴  Raquel Pascua-Maestro⁵  María Dolores Ganfornina⁵  Tamara García-Barrera⁶  José Luis Gómez-Ariza⁶  Raquel Larramona-Arcas⁷  Elena Galea⁷  Miquel Vila⁷  Roser Masgrau⁷ 

[1] Alzheimer’s Disease Research Laboratory, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School;Cajal Institute, Consejo Superior de Investigaciones Científicas (CSIC);Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED);Departamento de Biología Celular, Genética y Fisiología, Facultad de Ciencias, Instituto de Investigación Biomedica de Málaga (IBIMA), Universidad de Málaga;Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Universidad de Valladolid-CSIC;Departamento de Química, Facultad de Ciencias Experimentales, Campus de El Carmen, Centro de Investigación en Recursos Naturales, Salud y Medio Ambiente (RENSMA), Universidad de Huelva;Unitat de Bioquímica de Medicina, Departament de Bioquímica i Biologia Molecular, and, Institut de Neurociències (INc), Facultat de Medicina, Universitat Autònoma de Barcelona;

关键词: APOE4;    Astrocytes;    Calcium signaling;    Sex;    Lysosome;    Purinergic receptors;   

DOI  :  10.1186/s13024-020-00382-8

来源: DOAJ

【 摘 要 】

Abstract Background The apolipoprotein E (APOE) gene exists in three isoforms in humans: APOE2, APOE3 and APOE4. APOE4 causes structural and functional alterations in normal brains, and is the strongest genetic risk factor of the sporadic form of Alzheimer’s disease (LOAD). Research on APOE4 has mainly focused on the neuronal damage caused by defective cholesterol transport and exacerbated amyloid-β and Tau pathology. The impact of APOE4 on non-neuronal cell functions has been overlooked. Astrocytes, the main producers of ApoE in the healthy brain, are building blocks of neural circuits, and Ca2+ signaling is the basis of their excitability. Because APOE4 modifies membrane-lipid composition, and lipids regulate Ca2+ channels, we determined whether APOE4 dysregulates Ca2+signaling in astrocytes. Methods Ca2+ signals were recorded in astrocytes in hippocampal slices from APOE3 and APOE4 gene targeted replacement male and female mice using Ca2+ imaging. Mechanistic analyses were performed in immortalized astrocytes. Ca2+ fluxes were examined with pharmacological tools and Ca2+ probes. APOE3 and APOE4 expression was manipulated with GFP-APOE vectors and APOE siRNA. Lipidomics of lysosomal and whole-membranes were also performed. Results We found potentiation of ATP-elicited Ca2+responses in APOE4 versus APOE3 astrocytes in male, but not female, mice. The immortalized astrocytes modeled the male response, and showed that Ca2+ hyperactivity associated with APOE4 is caused by dysregulation of Ca2+ handling in lysosomal-enriched acidic stores, and is reversed by the expression of APOE3, but not of APOE4, pointing to loss of function due to APOE4 malfunction. Moreover, immortalized APOE4 astrocytes are refractory to control of Ca2+ fluxes by extracellular lipids, and present distinct lipid composition in lysosomal and plasma membranes. Conclusions Immortalized APOE4 versus APOE3 astrocytes present: increased Ca2+ excitability due to lysosome dysregulation, altered membrane lipidomes and intracellular cholesterol distribution, and impaired modulation of Ca2+ responses upon changes in extracellular lipids. Ca2+ hyperactivity associated with APOE4 is found in astrocytes from male, but not female, targeted replacement mice. The study suggests that, independently of Aβ and Tau pathologies, altered astrocyte excitability might contribute to neural-circuit hyperactivity depending on APOE allele, sex and lipids, and supports lysosome-targeted therapies to rescue APOE4 phenotypes in LOAD.

【 授权许可】

Unknown