title: An amiloride-sensitive and voltage-dependent Na+ channel in an HLA-DR-restricted human T cell clone.
abstract: We investigated changes in voltage-gated Na+ currents and effects of extracellular Na+ on proliferation in HLA-DR-restricted human CD4+ alphabeta T cells after stimulation with a non-self antigenic peptide, M12p54-68. In the absence of antigenic peptide, neither single (n = 80) nor APC-contacted (n = 71) T cells showed voltage-gated inward currents recording with whole-cell patch-clamp techniques, even with Ca2+ and Na+ ions present in the perfusion solution. However, with the same recording conditions, 31% (26 of 84) of APC-contacted T cells stimulated with the antigenic peptide showed voltage-dependent inward currents that were elicited from -60 mV. The inward currents were not inhibited in extracellular Ca2+-free conditions or in the presence of 1 mM NiCl2. However, they were completely inhibited in extracellular Na+-free conditions, which were made by replacing Na+ with iso-osmotic N-methyl-d -glucamine or choline. The Na+ currents were insensitive to tetrodotoxin, a classical blocker of Na+ channels, but were dose-dependently inhibited by amiloride, a potassium-sparing pyrazine diuretic. Furthermore, the Ag-specific proliferative response of T cells was completely inhibited in Na+-free Tyrode's solution and was suppressed by amiloride in a dose-dependent manner. Our findings suggest that activation of amiloride-sensitive and voltage-gated Na+ channels would be an important step to allow an adequate influx of Na+ and maintain a sustained high Ca2+ level during T cell activation.
authors.affiliation: Department of Pharmacology, Kumamoto University School of Medicine, Japan. lai-zf@gpo.kumamoto-u.ac.jp
authors.forename: Z F
authors.initials: ZF
authors.lastname: Lai
authors.forename: Y Z
authors.initials: YZ
authors.lastname: Chen
authors.forename: Y
authors.initials: Y
authors.lastname: Nishimura
authors.forename: K
authors.initials: K
authors.lastname: Nishi
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000595:Amino Acid Sequence; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002999:Clone Cells; D005110:Extracellular Space / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D006684:HLA-DR Antigens / Q000276:immunology*; D006801:Humans; D007424:Intracellular Fluid / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D012964:Sodium / Q000378:metabolism / Q000502:physiology; D015222:Sodium Channels / Q000276:immunology* / Q000378:metabolism*; D012996:Solutions; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism*; D013779:Tetrodotoxin / Q000276:immunology / Q000494:pharmacology
chemical_list: D006684:HLA-DR Antigens; D011948:Receptors, Antigen, T-Cell; D015222:Sodium Channels; D012996:Solutions; D013779:Tetrodotoxin; D000584:Amiloride; D012964:Sodium; D002118:Calcium