Voltage-gated potassium channels are required for human T lymphocyte activation.
The calcium channel blockers, verapamil and diltiazem, inhibit phytohemagglutinin (PHA)-induced mitogenesis at concentrations that block the T lymphocyte K channel currents. K channel blockers also inhibit the allogeneic mixed lymphocyte response in a dose-dependent manner with the same potency sequence as for block of K currents. K channel blockers inhibit PHA-stimulated mitogenesis only if added during the first 20-30 h after PHA addition, but not later, indicating a requirement for functional K channels during this period. We investigated the effect of K channel blockers on various aspects of protein synthesis for two reasons: first, protein synthesis appears to be necessary for the events leading to DNA synthesis, and second, the increase in the protein synthetic rate commences during the first 24-48 h after PHA addition. PHA-induced total protein synthesis was reduced to the level in unstimulated T lymphocytes by K channel blockers in a dose-dependent manner with the same potency sequence as for the block of K currents and inhibition of [3H]thymidine incorporation. Two-dimensional gel electrophoresis demonstrated that although the synthesis of the majority of proteins was reduced by K channel blockers to the level in unstimulated T cells, some proteins continued to be synthesized at an enhanced rate compared with resting cells. Two proteins, S and T, detected by two-dimensional gel electrophoresis in unstimulated T lymphocytes, appeared to be reduced in intensity in gels of PHA-treated T lymphocytes, in contrast to the increased synthesis of the remaining proteins. 4-Aminopyridine (4-AP), at concentrations that inhibit protein synthesis, prevented the apparent PHA-induced reduction of proteins S and T. These proteins may play a role in maintaining the T lymphocyte in a resting state and may be related to the translation inhibitory factors reported to be present at a higher specific activity in quiescent T lymphocytes than in PHA-activated T cells. The expression of the IL-2 receptor (Tac) during T lymphocyte activation was not altered by K channel blockers, whereas the production of interleukin 2 (IL-2) was reduced to the level in unstimulated T lymphocytes. Exogenous IL-2 partially relieved the inhibition of mitogenesis by low, but not by high, concentrations of 4-AP. These experiments clarify the role of K channels in T lymphocyte activation and suggest that functional K channels are required either for protein synthesis or for events leading to protein synthesis.
D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology; D002460:Cell Line; D004110:Diltiazem / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007376:Interleukin-2 / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects; D007959:Lymphocyte Culture Test, Mixed; D010835:Phytohemagglutinins / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D014176:Protein Biosynthesis; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism; D014700:Verapamil
D000631:Aminopyridines; D007376:Interleukin-2; D007473:Ion Channels; D010835:Phytohemagglutinins; D015761:4-Aminopyridine; D014700:Verapamil; D004110:Diltiazem; D007930:Leucine; D011188:Potassium; D013936:Thymidine