Altered sarcoplasmic reticulum calcium transport in the presence of the heavy metal chelator TPEN
| Autor: | Ernst Niggli, László Csernoch, Cecilia Simut, Beatrix Dienes, János Almássy, Tamás Deli, Carole Jung, Istvan Jona, Péter Szentesi, Monika Sztretye |
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| Jazyk: | angličtina |
| Rok vydání: | 2009 |
| Předmět: |
SERCA
Physiology Muscle Fibers Skeletal Iron Chelating Agents Metal Chelator Membrane Potentials Sarcoplasmic Reticulum Calcium-Transporting ATPases Animals Calcium Signaling Elméleti orvostudományok Lipid bilayer Molecular Biology Ryanodine receptor Chemistry Endoplasmic reticulum Rana esculenta Ryanodine Receptor Calcium Release Channel Cell Biology Orvostudományok Ethylenediamines Rats Dissociation constant Cytosol Biochemistry Biophysics Calcium Intracellular |
| Popis: | TPEN (N,N,N',N'-tetrakis(2-pyridylmethyl)-ethylenediamine) is a membrane-permeable heavy-metal ion chelator with a dissociation constant for Ca2+ comparable to the Ca2+ concentration ([Ca2+]) within the intracellular Ca2+ stores. It has been used as modulator of intracellular heavy metals and of free intraluminal [Ca2+], without influencing the cytosolic [Ca2+] that falls in the nanomolar range. In our previous studies, we gave evidence that TPEN modifies the Ca2+ homeostasis of striated muscle independent of this buffering ability. Here we describe the direct interaction of TPEN with the ryanodine receptor (RyR) Ca2+ release channel and the sarcoplasmic reticulum (SR) Ca2+ pump (SERCA). In lipid bilayers, at negative potentials and low [Ca2+], TPEN increased the open probability of RyR, while at positive potentials it inhibited channel activity. On permeabilized skeletal muscle fibers of the frog, but not of the rat, 50 microM TPEN increased the number of spontaneous Ca2+ sparks and induced propagating events with a velocity of 273 +/- 7 microm/s. Determining the hydrolytic activity of the SR revealed that TPEN inhibits the SERCA pump, with an IC(50) = 692 +/- 62 microM and a Hill coefficient of 0.88 +/- 0.10. These findings provide experimental evidence that TPEN directly modifies both the release of Ca2+ from and its reuptake into the SR. |
| Databáze: | OpenAIRE |
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