Effective and free calcium diffusion inside cells

CECILIA VILLARRUEL; PABLO S. AGUILAR; SILVINA PONCE DAWSON

Ouro Preto, MG

Congreso; Encontro de Outono da Sociedade Brasileira de Fisica; 2023

Sociedade Brasileira de Fisica

Calcium (Ca2+) is a universal second messenger that participates in the regulation of an enormous variety of physiological processes. The way in which local elevations of the cytosolic Ca2+ concentration spread in space and time is key for the versatility of the signals. Ca2+ diffusion in the cytosol is hindered by its interaction with proteins that act as buffers. Depending on the concentrations and the kinetics of the interactions, there is a large range of values at which Ca2+ diffusion can effectively proceed. Having reliable estimates of this range, particularly of its highest end, which corresponds to the ions free diffusion, is key to understand how the signals propagate. In this talk I will present a brief overview of Ca2+ signals and of the effective transport of the ions in the presence of buffers together with experimental results with which we could quantify the Ca2+-free diffusion coefficient directly in the cytosol of living cells. These results, obtained using Fluorescence Correlation Spectroscopy in Xenopus laevis oocytes and in cells of Saccharomyces cerevisiae, show that the ions can freely diffuse in the cytosol at a higher rate than previously thought. This has important implications for the propagation of the signals and the end responses that they can elicit.