Chloride-channel block inhibits T lymphocyte activation and signalling.
Both large- and small-conductance chloride (Cl-) channels have been found in human T lymphocytes; however, apart from possible roles in mediating regulatory volume decrease, their functions are not understood. We have used patch-clamp electrophysiology, Ca2+ spectrofluorometry, and Western blot assay for phosphotyrosine to investigate the effects of blocking Cl- channels on proliferation and on specific events in the activation of normal human T cells. Four chemically distinct Cl- channel blockers inhibited both the small-conductance Cl- channels and phytohemagglutinin (PHA)-induced lymphocyte proliferation in a similar dose-dependent manner; their order of potency was 5-nitro-2(3-phenylpropylamino)-benzoic acid (NPPB) > 4,4'-diisothiocyano-2,2'-disulfonic acid (DIDS) > flufenamic acid >> IAA-94. The Cl- channel blockers inhibited both the PHA-induced mobilization of Ca2+ and the rapid tyrosine phosphorylation of several polypeptides. Cell proliferation was not rescued by the Ca+ ionophore ionomycin or by addition of exogenous interleukin-2 (IL-2). Moreover, the blockers also inhibited phosphotyrosine expression in IL-2-treated, activated lymphoblasts. Thus, our results support a role for Cl- channels in early, PHA-evoked signalling and in later, II-2-dependent stages of lymphocyte activation and proliferation.
Phipps
D J
DJ
Toronto Hospital Research Institute, Ontario, Canada.
Branch
D R
DR
Schlichter
L C
LC
D015153:Blotting, Western; D002118:Calcium / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000276:immunology; D018118:Chloride Channels / Q000037:antagonists & inhibitors*; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D015398:Signal Transduction / Q000276:immunology*; D013050:Spectrometry, Fluorescence; D013601:T-Lymphocytes / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism
D018118:Chloride Channels; D007166:Immunosuppressive Agents; D007376:Interleukin-2; D014443:Tyrosine; D002118:Calcium