ИСТИНА

In recent years, leukemia-lymphoma cell lines are extensively used as appropriate cellular models to study the role of ion-transporting systems in hematologic malignancies. Sodium channel activity in leukemia-lymphoma cell lines was directly controlled by submembranous actin cytoskeleton. Biophysical characteristics of non-voltage-gated sodium channels in leukemia cell lines were similar to that of ENaCs. Consistently, an expression of alpha-, beta-, gamma-hENaC subunits in K562 and U937 cells was detected using RT-PCR and immunofluorescent staining. However, we showed that amiloride, known inhibitor of ENaC, did not block single sodium channels and integral currents. Interestingly, we found that sodium channel activity was drastically increased in response to extracellular application of trypsin (5 mkg/ml). Taken together, our observations suggest that amiloride-insensitive sodium channels in K562 and U937 cells belong to the ENaC family. We conclude that cortical actin structures represent the main factor that controls the activity of ENaC-like channels in human leukemic cells.