ACTIVITY OF ATPases IN POSTMITOСHONDRIAL FRACTION OF LYMPHOMA NK/Ly CELLS UNDER BAFILOMICINE AND NAADP PRESENCE

The system of active of transport of ions (ATPases) plays a critical role in cancer cells and is a potential target of anticancer therapy. A selective V-type H + -ATPase in- hibitor ? bafilomicine (Baf1A) was intensively studied as anticancer drug. It is known that H-ATPase creates the electrochemical gradients in the membranes of endo-lyso- somal cells. These acidic stores are also Ca 2+ -containing organelles. The nicotinic acid adenine dinucleotide phosphate (NAADP) is a mediator of intracellular calcium signa? ling pathways. The role of NAADP-induced Ca 2+ transient in cancer cells is not under- stood. It’s correlation with activity of different ATPases in tumor cells is also poorly stud- ied. The main goal of our study was to investigate the effects of Baf1A and NAADP on the activity of Na + /K + -ATPase, basal Mg 2+ -ATPase and Ca 2+ -ATPase of plasma mem- brane (PMCA) and endoplasmatic reticulum (SERCA) of NK/Ly murine lymphoma cells. All experiments were conducted on the postmitochondrial fraction of NK/Ly cells. We found that Baf1A (1 μМ) did not cause changes in activity of ATPase in postmitochon- drial fraction of NK/Ly cells. It was revealed that NAADP (7 μМ) caused an increase of Na + /K + -ATPase activity by (54.18±7.84)% (n = 6, Р?0.05) and PMCA by 3-fold (Р?0.05) in subcellular fractions of NK/Ly cells. The activity of SERCA in membrane of cancer cells, as well as basal ATPase activity, were not changed upon NAADP application. Ad- dition of Baf1A to the subcellular fraction of NK/Ly cells enhanced NAADP-induced in- crease in PMCA activity by 9.4-fold (n = 5, Р?0.05), but NAADP-induced increase in Na + /K + -ATPase activity was slackened. We suggest that H + -ATPase functions indepen- dently on Na + /K + -ATPase as well as other ATPases identified in lymphoma membranes, due to its localization on cell surface. We found a correlation between the Н + -ATPase activity and pumps of PM (PMCA and Na + /K + -ATPase) only in presence of NAADP in subcellular fraction of NK/Ly cells. We consider that membranes of acidic stores are associated with PM in tumor cells.