Extracellular protease trypsin activates amiloride‐insensitive sodium channels in human leukemia cells

摘要

Abstract Sodium influx is tightly regulated in the cells of blood origin. Amiloride‐insensitive sodium channels were identified as one of the main sodium‐transporting pathways in leukemia cells. To date, all known regulatory pathways of these channels are coupled with intracellular actin cytoskeleton dynamics. Here, to search for physiological mechanisms controlling epithelial Na + channel (ENaC)‐like channels, we utilized leukemia K562 cells as a unique model to examine single channel behavior in a whole‐cell patch‐clamp experiments. We have shown for the first time that extracellular serine protease trypsin directly activates sodium channels in plasma membrane of K562 cells. The whole‐cell single current recordings clearly demonstrate no inhibition of trypsin‐activated channels by amiloride or benzamil. Involvement of proteolytic cleavage in channel opening was confirmed in experiments with soybean trypsin inhibitor. More importantly, stabilization of F‐actin with intracellular phalloidin did not prevent trypsin‐induced channel activation indicating no implication of cytoskeleton rearrangements in stimulatory effect of extracellular protease. Our data reveals a novel mechanism modulating amiloride‐insensitive ENaC‐like channel activity and integral sodium permeability in leukemia cells.