title: Microglia release ATP by exocytosis.
abstract: Microglia survey the brain environment by sensing several types of diffusible molecules, among which extracellular nucleotides released/leaked from damaged cells have central roles. Microglia sense ATP or other nucleotides by multiple P2 receptors, after which they change into several different phenotypes. However, so far, it is largely unknown whether microglia themselves release ATP and, if so, by what mechanism. Here we show that exocytosis is the mechanism by which microglia release ATP. When we stimulated microglia with ionomycin, they released ATP and the release was dependent on Ca²⁺, vesicular H⁺-ATPase, or SNAREs but independent of connexin/pannexin hemichannels. VNUT was found to be expressed in microglia and exhibited no colocalization with lysosome. We also visualized the exocytosis of ATP by a quinacrine-based fluorescent time-lapse imaging. Moreover, we found that lipopolysaccharide increased the ionomycin-induced release of ATP, which was dependent on the increase in VNUT. Taken together, our data suggested that exocytosis is the mechanism of ATP release from microglia. When activated, they would release ATP by increasing VNUT-dependent exocytotic mechanisms.
authors.affiliation: Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Shimokato, Chuo, Yamanashi, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Imura
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Morizawa
authors.forename: Ryohei
authors.initials: R
authors.lastname: Komatsu
authors.forename: Keisuke
authors.initials: K
authors.lastname: Shibata
authors.forename: Youichi
authors.initials: Y
authors.lastname: Shinozaki
authors.forename: Hirotake
authors.initials: H
authors.lastname: Kasai
authors.forename: Kohji
authors.initials: K
authors.lastname: Moriishi
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Moriyama
authors.forename: Schuichi
authors.initials: S
authors.lastname: Koizumi
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D005089:Exocytosis / Q000502:physiology*; D017628:Microglia / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000255:Adenosine Triphosphate
keywords: ATP; VNUT; exocytosis; microglia