Extracellular ATP induces unconventional release of glyceraldehyde-3-phosphate dehydrogenase from microglial cells.
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key glycolytic enzyme that is predominantly localized in the cytoplasm. However, recent studies have suggested that GAPDH is released by various cells and that extracellular GAPDH is involved in the regulation of neuritogenesis in neuronal cells. It has also been reported that GAPDH is expressed on the surfaces of macrophages and functions as a transferrin receptor. However, since GAPDH is a leaderless protein the mechanisms by which it reaches the extracellular environment remain unclear. Here, we examined the role of P2X7 receptor (P2X7R), an ATP-gated cation channel, in the unconventional release of GAPDH from microglial cells, the resident macrophages in the brain. The activation of P2X7R by ATP triggered GAPDH release from lipopolysaccharide (LPS)-primed microglial cells. ATP-induced microvesicle formation, exosome release, and K(+) efflux followed by caspase-1 activation are likely involved in the GAPDH release, but ATP-induced dilatation of membrane pores and lysosome exocytosis are not. It was also demonstrated that exogenous GAPDH facilitated LPS-induced phosphorylation of p38 MAP kinase in microglial cells. These findings suggest that P2X7R plays an important role in the unconventional release of GAPDH from microglial cells, and the GAPDH released into the extracellular space might be involved in the regulation of the neuroinflammatory response in the brain.
Animal Immune and Cell Biology Research Unit, Division of Animal Sciences, National Institute of Agrobiological Sciences, 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan. Electronic address: ttakenou@affrc.go.jp.
Takato
T
Takenouchi
Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
Mitsutoshi
M
Tsukimoto
Prion Disease Research Center, National Institute of Animal Health, 3-1-5 Kannondai, Tsukuba, Ibaraki 305-8602, Japan.
Yoshifumi
Y
Iwamaru
Department of Physiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan.
Shuei
S
Sugama
Division of Sensory and Motor Systems, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-0057, Japan.
Kazunari
K
Sekiyama
Animal Immune and Cell Biology Research Unit, Division of Animal Sciences, National Institute of Agrobiological Sciences, 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan.
Mitsuru
M
Sato
Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
Shuji
S
Kojima
Division of Sensory and Motor Systems, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-0057, Japan.
Makoto
M
Hashimoto
Animal Immune and Cell Biology Research Unit, Division of Animal Sciences, National Institute of Agrobiological Sciences, 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan. Electronic address: kitani@affrc.go.jp.
Hiroshi
H
Kitani
D000255:Adenosine Triphosphate / Q000378:metabolism*; D020170:Caspase 1 / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D005089:Exocytosis / Q000276:immunology; D005110:Extracellular Space; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008070:Lipopolysaccharides / Q000276:immunology; D008247:Lysosomes / Q000276:immunology / Q000378:metabolism; D017628:Microglia / Q000276:immunology* / Q000378:metabolism*; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism; D061251:Primary Cell Culture; D058486:Receptors, Purinergic P2X7 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D008070:Lipopolysaccharides; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D048051:p38 Mitogen-Activated Protein Kinases; D020170:Caspase 1; D011188:Potassium
Glyceraldehyde-3-phosphate dehydrogenase; Microglial cells; P2X7 receptor; Unconventional release