Modulation of plasma membrane calcium ATPase (PMCA) by cortical actin cytoskeleton in living cells.

VIGIL, M.; FARAJ, S; PICO, M; RINALDI, D.E; MANGIALAVORI, I.; ROSSI, R.C; REY, O; ROSSI, J.P.; FERREIRA GOMES, M

Rosario, Santa Fe

Congreso; L Reunión Anual SAB 2022; 2022

The associations between the cortical cytoskeleton and the elements of the plasmamembrane are currently not only considered to be structural and mechanical in naturebut are now recognized as dynamic interrelationships that modulate cellular responses.We recently explained a new regulatory mechanism of plasma membrane Ca2+-ATPase(PMCA) in which the actin cytoskeleton could participate in the regulation of cytosolicCa2+ ([Ca2+]cyt) homeostasis.To assess whether this regulatory mechanism may have physiological relevance, wedecided to further characterize it in a living cell by monitoring changes in actin and[Ca2+]cyt polymerization. We used HEK293T cells that expressed PMCA transiently. Thedynamics of [Ca2+]cyt were performed using the Fluo-4 fluorescent probe, whereas theactin dynamic in cells was visualized by transiently expressing LifeAct-Ruby. The transientheight [Ca2+]cyt was generated by the release of Ca2+ from the endoplasmic reticulum(ER) or by the influx of extracellular Ca2+ via storage-operated Ca2+ channels (SOC).Results show that the increase of [Ca2+]cyt resulting from ER and extracellular media wassignificantly attenuated in cells that overexpressed the hPMCA2 or hPMCA4 isoforms.Furthermore, the increase of [Ca2+]cyt induced actin polymerization in the nuclearperiphery and depolymerization in cortical regions only when Ca2+ enters through theSOC. This actin reorganization also occurred when PMCA was overexpressed, although inthese cells the height of [Ca2+]cyt was lower. To explore the results, we design a kineticmodel that explains PMCA activity and its activation in the [Ca2+]cyt functionality. The model was fitted to the experimental data and shows that PMCA activity increases while actin depolymerizes in cortical regions.These results suggest that actin reorganization is triggered by the rise of [Ca2+]cyt and that PMCA could be activated by the depolymerization of cortical actin in cells to restorethe basal level of [Ca2+]cyt.