Impact of natural flavonoid gossypin on P-ATPases: a potential selective inhibitor of the Plasma Membrane Ca2+-ATPase

ONTIVEROS M; TOMISAKI M; LORI F; NICOLE CERF; MÓNICA R. MONTES; ROLANDO C.ROSSI; ROSSI JUAN PABLO; MARIELA FERREIRA GOMES

Congreso; Reunión anual Sociedad Argentina de Biofísica; 2023

Flavonoids are multi-targeted compounds with antioxidant, anti-inflammatory, andanticancer effects, as well as the ability to modulate the essential functions of cellularenzymes, including P-ATPase [1]. In our laboratory, we studied the effect of flavonoids onplasma membrane calcium ATPase (PMCA4), a calmodulin-regulated P-ATPase thatmaintains intracellular Ca2+ homeostasis and links Ca2+ transport to ATP hydrolysis ineukaryotic cells [2].The importance of finding specific inhibitors is that it is essential to understand theimportance of an enzyme in many biological processes; since specific and potentinhibitors of PMCA4 do not exist yet, we have investigated several P-ATPases and analyzeddifferent flavonoids as inhibitors.We found that some flavonoids such as quercetin and gossypin (gossypetin-8-Oglucoside)inhibited PMCA4 activity. However, gossypin appeared as a potent inhibitor ofPMCA4 activity (Ki = 5 μM). In a previous publication, we showed that gossypin inhibitsPMCA4 via a gossypin -Mg2+ complex. We then tested the specificity of gossypin againstother major P-ATPases. We found that gossypin had little or no inhibitor effect on sarco/endoplasmic Ca2+-ATPase (SERCA), Na+/K+-ATPase, Mg2+-ATPase, and gastric H+/K+-ATPase, suggesting that it is probably specific for PMCA4.By using gossypin it was then possible to estimate the activity of PMCA4 in a complexsystem with the contribution of ATPase activity from other ATPases present in a microsomesample obtained from sf9 cells that overexpress human isoform 4b.In conclusion, these results indicate that gossypin is a potential candidate to be a specificinhibitor, opening to use as a tool to identify the role of PMCA4 in complex systems.