Role of KCa3.1 Channels in Modulating Ca2+ Oscillations during Glioblastoma Cell Migration and Invasion.

Cell migration and invasion in glioblastoma (GBM), the most lethal form of primary brain tumors, are critically dependent on Ca2+ signaling. Increases of [Ca2+]i in GBM cells often result from Ca2+ release from the endoplasmic reticulum (ER), promoted by a variety of agents present in the tumor microenvironment and able to activate the phospholipase C/inositol 1,4,5-trisphosphate PLC/IP3 pathway. The Ca2+ signaling is further strengthened by the Ca2+ influx from the extracellular space through Ca2+ release-activated Ca2+ (CRAC) currents sustained by Orai/STIM channels, meant to replenish the partially depleted ER. Notably, the elevated cytosolic [Ca2+]i activates the intermediate conductance Ca2+-activated K (KCa3.1) channels highly expressed in the plasma membrane of GBM cells, and the resulting K⁺ efflux hyperpolarizes the cell membrane. This translates to an enhancement of Ca2+ entry through Orai/STIM channels as a result of the increased electromotive (driving) force on Ca2+ influx, ending with the establishment of a recurrent cycle reinforcing the Ca2+ signal. Ca2+ signaling in migrating GBM cells often emerges in the form of intracellular Ca2+ oscillations, instrumental to promote key processes in the migratory cycle. This has suggested that KCa3.1 channels may promote GBM cell migration by inducing or modulating the shape of Ca2+ oscillations. In accordance, we recently built a theoretical model of Ca2+ oscillations incorporating the KCa3.1 channel-dependent dynamics of the membrane potential, and found that the KCa3.1 channel activity could significantly affect the IP3 driven Ca2+ oscillations. Here we review our new theoretical model of Ca2+ oscillations in GBM, upgraded in the light of better knowledge of the KCa3.1 channel kinetics and Ca2+ sensitivity, the dynamics of the Orai/STIM channel modulation, the migration and invasion mechanisms of GBM cells, and their regulation by Ca2+ signals.