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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 91: Computational Biophysics (joint session BP/CPP)

CPP 91.1: Vortrag

Donnerstag, 19. März 2020, 09:30–09:45, SCH A251

Effectiveness of Ca²⁺ clearance by PMCA pumps — •Barbara Schmidt¹, Cristina Constantin², Bernd Fakler², and Heiko Rieger¹ — ¹Center for Biophysics and Department of Theoretical Physics, Saarland University, 66123 Saarbrücken, Germany — ²Institute of Physiology, University of Freiburg, 79104 Freiburg, Germany

Ca²⁺ influx through voltage-gated (Cav) channels leads to an increase in the intracellular Ca²⁺-concentration ([Ca²⁺]_i) that can be monitored by BK-type Ca²⁺-activated K⁺ channels. Due to their gating kinetics they may be used as sensors for [Ca²⁺]_i underneath the plasma membrane. Here, K⁺ currents through BK channels were used to determine the Ca²⁺ transport activity of Ca²⁺-ATPases of the plasma membrane (PMCA), the classical Ca²⁺ pumps. Experimentally we monitored PMCA-mediated Ca²⁺ clearance by the decay of BK-currents following their activation by a short (0.8 ms) period of Ca²⁺-influx through Cav2.2 channels. Our theoretical model describes the Ca²⁺ diffusion within a spherical cell. Time- and Ca²⁺ concentration-dependent boundary conditions model the initial Ca²⁺ influx and the following outflow via the PMCA pumps. The time scale of this diffusion process is used to predict the strength of the PMCA pumps. Based on the experimentally determined density of Cav channels and PMCA pumps within the membrane we predict a PMCA pump strength that is at least 1.5 orders of magnitude larger than what has been assumed so far.