Glycine modulates membrane potential, cell volume, and phagocytosis in murine microglia.
Phagocytes form engulfment pseudopodia at the contact area with their target particle by a process resembling cell volume (CV) regulatory mechanisms. We evaluated whether the osmoregulatory active neutral amino acid glycine, which contributes to CV regulation via activation of sodium-dependent neutral amino acid transporters (SNATs) improves phagocytosis in isotonic and hypertonic conditions in the murine microglial cell line BV-2 and primary microglial cells (pMG). In BV-2 cells and pMG, RT-PCR analysis revealed expression of SNATs (Slc38a1, Slc38a2), but not of GlyRs (Glra1-4). In BV-2 cells, glycine (5 mM) led to a rapid Na(+)-dependent depolarization of membrane potential (V mem). Furthermore, glycine increased CV by about 9%. Visualizing of phagocytosis of polystyrene microspheres by scanning electron microscopy revealed that glycine (1 mM) increased the number of BV-2 cells containing at least one microsphere by about 13%. Glycine-dependent increase in phagocytosis was suppressed by the SNAT inhibitor α-(methylamino)isobutyric acid (MeAIB), by replacing extracellular Na(+) with choline, and under hypertonic conditions, but not by the GlyR antagonist strychnine or the GlyR agonist taurine. Interestingly, hypertonicity-induced suppression of phagocytosis was rescued by glycine. These findings demonstrate that glycine increases phagocytosis in iso- and hypertonic conditions by activation of SNATs.
Department of Cell Biology, University of Salzburg, Hellbrunnerstr. 34, 5020, Salzburg, Austria.
Barbara
B
Komm
Marlena
M
Beyreis
Michael
M
Kittl
Martin
M
Jakab
Markus
M
Ritter
Hubert H
HH
Kerschbaum
D026924:Amino Acid Transport System A / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D002794:Choline / Q000494:pharmacology; D005998:Glycine / Q000494:pharmacology*; D018684:Glycine Agents / Q000494:pharmacology; D006982:Hypertonic Solutions; D008564:Membrane Potentials / Q000187:drug effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000166:cytology; D008863:Microspheres; D010587:Phagocytosis / Q000187:drug effects*; D011137:Polystyrenes; D061251:Primary Cell Culture; D012333:RNA, Messenger / Q000096:biosynthesis; D018009:Receptors, Glycine / Q000819:agonists / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D013331:Strychnine / Q000494:pharmacology; D013654:Taurine / Q000494:pharmacology; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000494:pharmacology
D026924:Amino Acid Transport System A; C000657605:Glra1 protein, mouse; D018684:Glycine Agents; D006982:Hypertonic Solutions; D011137:Polystyrenes; D012333:RNA, Messenger; D018009:Receptors, Glycine; C432411:Slc38a1 protein, mouse; C498798:Slc38a2 protein, mouse; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D013654:Taurine; D013331:Strychnine; D002794:Choline; D005998:Glycine