Microglia derived from the axotomized adult rat facial nucleus uptake glutamate and metabolize it to glutamine in vitro.
Microglia in the axotomized adult rat facial nucleus (axoFN) have been shown to highly express a glutamate transporter (GLT-1). The microglia appear to serve as glutamate (Glu) scavengers in the axoFN. However, there is no evidence that the microglia actually have the ability to uptake Glu and convert it to Gln. In this study, we investigated whether axoFN-derived microglia (axoFN-microglia) can uptake Glu and metabolize it to Gln. Microglia obtained by explant culture of axoFN on poly(N-isopropylacrylamide)-grafted dishes were non-invasively sub-cultured onto dishes or wells. Immunoblotting and Glu-uptake experiments revealed that the axoFN-microglia uptake14C-Glu mainly by GLT-1 activity. Immunoblotting and immunocytochemical methods clarified that axoFN-microglia express the Gln synthetase (GS) protein in the same manner as newborn rat brain-derived primary microglia (NRB-microglia). Biochemical analysis demonstrated that the specific activity of GS of axoFN-microglia is similar to that of NRB-microglia, suggesting that these microglia play equivalent roles in the metabolic conversion of Glu to Gln. Nuclear magnetic resonance analysis clarified that NRB-microglia metabolize [13C]Glu to [13C]Gln depending on the incubation time, inferring the similar potential of axoFN-microglia. Taken together, these results demonstrate that axoFN-microglia express functional GLT-1 and GS proteins, and are strongly suggested to serve as Glu scavengers in vivo.
Department of Science and Engineering for Sustainable Innovation, Faculty of Science and Engineering, Soka University, Tokyo 192-8577, Japan. Electronic address: nakajima@t.soka.ac.jp.
Kazuyuki
K
Nakajima
Department of Science and Engineering for Sustainable Innovation, Faculty of Science and Engineering, Soka University, Tokyo 192-8577, Japan.
Tomoyuki
T
Kanamatsu
Department of Science and Engineering for Sustainable Innovation, Faculty of Science and Engineering, Soka University, Tokyo 192-8577, Japan.
Maasa
M
Koshimoto
National Institute of Neuroscience, Tokyo 187-8502, Japan.
Shinichi
S
Kohsaka
D000375:Aging; D027322:Amino Acid Transport System X-AG / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport; D002478:Cells, Cultured; D065828:Facial Nucleus / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D008297:Male; D017628:Microglia / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D017208:Rats, Wistar
D027322:Amino Acid Transport System X-AG; D005973:Glutamine; D018698:Glutamic Acid
Axotomized facial nucleus; Glutamate transporter; Glutamine synthetase; Microglia; Nuclear magnetic resonance