BPCPPDYSOE21 – scientific programme

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BP: Fachverband Biologische Physik

BP 11: Poster A: Single Molecule, Multicellular, Bioimaging, Focus Sessions, etc.

BP 11.1: Poster

Monday, March 22, 2021, 16:30–19:00, BPp

How fast do PMCA pumps transport Ca²⁺? — •Barbara Schmidt¹, Cristina E. Constantin², Bernd Fakler², and Heiko Rieger¹ — ¹Center for Biophysics and Dep. Theoretical Physics, Saarland University, 66123 Saarbrücken, Germany — ²Institute of Physiology, University of Freiburg, 79104 Freiburg, Germany

Plasma membrane protein complexes of two PMCA subunits and two Neuroplastin or Basigin proteins are responsible for Ca²⁺ ion transport out of cells. Here we make use of BK-type Ca²⁺-activated K⁺ channels to determine the Ca²⁺ transport activity of PMCA. Due to their large conductance and their particular gating kinetics the BK channels may be used as fast and reliable sensors for intracellular Ca²⁺-concentration ([Ca²⁺]_i) beneath the plasma membrane. Experimentally we monitor the PMCA-mediated Ca²⁺ clearance (or transport) by the decay of BK-currents following their activation by a short (0.8 ms) period of Ca²⁺-influx through Cav2.2 channels. To relate the experimentally observed temporal evolution of the K⁺ current to the underlying temporal evolution of the Ca²⁺ concentration we implement a theoretical model for the Ca²⁺-dependence of the BK-current and of the PMCA pump strength. The maximum PMCA pump strength is used to fit the predicted time course of the K⁺ current to the experimental data, which turns out to be at least 2 orders of magnitude larger than what has been assumed so far. Implication of this finding for Ca²⁺ signaling in general are discussed.