Book of Abstracts - New Frontiers 2022

Abstracts of poster presentations

BLOCKING EFFECT OF THE FERRITIN NANOPARTICLE ON THE CARDIAC RYANODINE RECEPTOR

J. Gaburjakova 1 , M. Gaburjakova 1 , E. Krejciova 1 , S. Nagy 2 , D. Kosnac 3,4 , M. Kopani 3

1 Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Bratislava, Slovakia; 2 Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Bratislava, Slovakia; 3 Institute of Medical Physics, Biophysics, Informatics and Telemedicine, Faculty of Medicine, Comenius University, Bratislava, Slovakia; 4 Department of Simulation and Virtual Medical Education, Faculty of Medicine, Comenius University, Bratislava, Slovakia Iron, an essential element for most living organisms, participates in a wide variety of physiological processes. Disturbance in iron homeostasis has been associated with numerous pathologies, particularly in the heart and brain, which are the most susceptible organs. Given a critical role of iron in cell functioning, its labile concentration in the cytoplasm has to be tightly controlled and regulated to prevent both iron deficiency and overload. The cellular iron is stored and sequestered in ferritin complexes (nonheme protein), mainly located in the cytoplasm. Ferritin consists of a roughly spherical protein shell with an outer diameter of 12 – 13 nm and with an inner cavity diameter no greater than 8 nm, where iron is kept in a non toxic and bioavailable form. Under iron-overload conditions, the generation of reactive oxygen species leads to impairment in Ca 2+ signaling, fundamentally implicated in cardiac physiology. Since iron excess is accompanied by increased expression of ferritin, we examined whether ferritin functionally interacts with the cardiac ryanodine receptor (RYR2), which is one of the major components of Ca 2+ signaling in the heart. Using the method of planar lipid membranes, we show that cytosolic ferritin induced an abrupt, permanent blockage of the RYR2 channel. The ferritin effect was strongly voltage dependent and competitively antagonized by cytosolic TEA+, an impermeant RYR2 blocker. Our results collectively indicate that monomeric ferritin highly likely blocks the RYR2 channel by a direct electrostatic interaction within the wider region of the channel permeation pathway. Magnetic field as a contributing factor was excluded, because we calculated that energy of even bigger clusters of ferritin nanoparticles in the Earth`s magnetic field is at least one order smaller than the thermal energy. We tested a wide range of ferritin concentrations (0.005 –0.30 µg/ml) covering physiological and iron -overload situations. Although, ferritin caused RYR2 blockage in both cases, it seems highly unlikely that ferritin-RYR2 interaction occurs when iron homeostasis is maintained. Otherwise, it could significantly weaken or even abolish Ca 2+ release that is required for cardiac contraction. As yet, there has been no precise examination of ferritin localization in the cytoplasm. Under iron-overload conditions, however, there is a greater chance of collisions between the ferritin nanoparticles and RYR2 channels, because ferritin concentration becomes increased. Thus, we can conclude that RYR2 blockage by ferritin might significantly contribute to abnormal cardiac Ca 2+ signaling.

Keywords: cardiac ryanodine receptor, ferritin, ion channel blockage, iron homeostasis

Funding: This work was supported by VEGA 2/0018/21, VEGA 2/0008/20, VEGA 1/0173/20, APVV 16 – 0039, ITMS 26230120009.

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