BPCPPDYSOE21 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 11: Poster A: Single Molecule, Multicellular, Bioimaging, Focus Sessions, etc.
BP 11.1: Poster
Montag, 22. März 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.