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Potassium channels in human NK cells are involved in discrete stages of the killing process
Abstract:
Using the whole-cell variation of the patch-clamp technique, we have found a voltage-dependent K+ current in human natural killer (NK) cells. This K+ current is reduced in a dose-dependent manner by a variety of ion-channel blockers (verapamil, quinidine, 4-aminopyridine, Cd2+) at concentrations comparable to those that inhibit natural killing. Pretreatment of target cells with quinidine or verapamil did not significantly reduce their sensitivity to killing, whereas substantial inhibition of killing was observed after pretreatment of effector cells. Both verapamil and quinidine reduced the proportion of effector-target cell conjugates, suggesting that K channels play a role in the "binding" phase of the killing process. By adding EDTA or channel blockers as various times in a Ca-pulse assay system, we have also delineated a blocker-sensitive phase of bound conjugates that strictly corresponds with the Ca-dependent "programming" stage of killing. In contrast, the killer cell-independent stage, which is Ca2+ independent, apparently does not require functioning K channels. Verapamil and quinidine do not affect target cell sensitivity to the putative soluble mediator of natural killing, natural killer cytotoxic factor (NKCF), but inhibit release of NKCF from NK cells. Thus, the data suggest that K channels in NK cells play essential roles in the natural killing process that include events in the "programming-for-lysis" phase leading to release of NKCF.
Insights
Voltage-dependent potassium (K+) channels in human natural killer (NK) cells are crucial for natural killing. Blocking these K+ channels inhibits NK cell binding, programming, and cytotoxic factor release, essential for the killing process.
Area of Science:
- Immunology
- Cellular Physiology
Background:
- Human natural killer (NK) cells are critical for innate immunity, mediating cytotoxic responses against target cells.
- The precise molecular mechanisms underlying NK cell-mediated cytotoxicity, particularly the role of ion channels, remain incompletely understood.
Purpose of the Study:
- To investigate the presence and function of voltage-dependent potassium (K+) currents in human NK cells.
- To determine the role of these K+ channels in the various stages of the natural killing process.
Main Methods:
- Whole-cell patch-clamp technique to record K+ currents in human NK cells.
- Application of various ion channel blockers (verapamil, quinidine, 4-aminopyridine, Cd2+) to assess their effects on K+ currents and NK cell functions.
- Ca-pulse assay system to delineate specific phases of the killing process.
Main Results:
- A voltage-dependent K+ current was identified in human NK cells.
- This K+ current was inhibited by ion channel blockers at concentrations that also inhibit natural killing.
- Blocking K+ channels impaired effector-target cell binding, the Ca2+-dependent programming stage, and the release of natural killer cytotoxic factor (NKCF).
Conclusions:
- Voltage-dependent K+ channels are essential components of the human NK cell cytotoxic machinery.
- These channels play critical roles in conjugate formation, target cell programming, and NKCF release during natural killing.