title: Phosphatidylserine Exposure Controls Viral Innate Immune Responses by Microglia.
abstract: Microglia are the intrinsic immune sentinels of the central nervous system. Their activation restricts tissue injury and pathogen spread, but in some settings, including viral infection, this response can contribute to cell death and disease. Identifying mechanisms that control microglial responses is therefore an important objective. Using replication-incompetent adenovirus 5 (Ad5)-based vectors as a model, we investigated the mechanisms through which microglia recognize and respond to viral uptake. Transgenic, immunohistochemical, molecular-genetic, and fluorescence imaging approaches revealed that phosphatidylserine (PtdSer) exposure on the outer leaflet of transduced cells triggers their engulfment by microglia through TAM receptor-dependent mechanisms. We show that inhibition of phospholipid scramblase 1 (PLSCR1) activity reduces intracellular calcium dysregulation, prevents PtdSer externalization, and enables months-long protection of vector-transduced, transgene-expressing cells from microglial phagocytosis. Our study identifies PLSCR1 as a potent target through which the innate immune response to viral vectors, and potentially other stimuli, may be controlled.
authors.affiliation: Waitt Advanced Biophotonics Center, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Tufail
authors.affiliation: Waitt Advanced Biophotonics Center, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Daniela
authors.initials: D
authors.lastname: Cook
authors.affiliation: Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Fourgeaud
authors.affiliation: Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Powers
authors.affiliation: Waitt Advanced Biophotonics Center, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Katharina
authors.initials: K
authors.lastname: Merten
authors.affiliation: Waitt Advanced Biophotonics Center, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Charles L
authors.initials: CL
authors.lastname: Clark
authors.affiliation: Waitt Advanced Biophotonics Center, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hoffman
authors.affiliation: Waitt Advanced Biophotonics Center, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Ngo
authors.affiliation: Waitt Advanced Biophotonics Center, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Kohei J
authors.initials: KJ
authors.lastname: Sekiguchi
authors.affiliation: Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Clodagh C
authors.initials: CC
authors.lastname: O'Shea
authors.affiliation: Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA; Immunobiology and Microbial Pathogenesis Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Greg
authors.initials: G
authors.lastname: Lemke
authors.affiliation: Waitt Advanced Biophotonics Center, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA. Electronic address: animmerj@salk.edu.
authors.forename: Axel
authors.initials: A
authors.lastname: Nimmerjahn
mesh_terms: D000256:Adenoviridae / Q000276:immunology*; D000257:Adenoviridae Infections / Q000276:immunology*; D000818:Animals; D055785:Gene Knockdown Techniques; D005822:Genetic Vectors / Q000276:immunology*; D007113:Immunity, Innate / Q000276:immunology*; D007150:Immunohistochemistry; D008822:Mice, Transgenic; D017628:Microglia / Q000276:immunology*; D009474:Neurons / Q000276:immunology* / Q000821:virology; D061848:Optical Imaging; D010587:Phagocytosis / Q000276:immunology*; D010718:Phosphatidylserines / Q000276:immunology*; D049294:Phospholipid Transfer Proteins / Q000235:genetics / Q000276:immunology*
chemical_list: D010718:Phosphatidylserines; D049294:Phospholipid Transfer Proteins; C493426:Plscr1 protein, mouse
keywords: TAM receptor; adenovirus; astrocytes; calcium; infection; microglia; phagocytosis; phosphatidylserine; phospholipid scramblase 1; two-photon imaging