Lanthanides Report Calcium Sensor in the Vestibule of Ryanodine Receptor

Sándor Sárközi, I. Komáromi, I. Jóna, János Almássy

Research output: Contribution to journalArticle

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Abstract

Ca2+ regulates ryanodine receptor's (RyR) activity through an activating and an inhibiting Ca2+-binding site located on the cytoplasmic side of the RyR channel. Their altered sensitivity plays an important role in the pathology of malignant hyperthermia and heart failure. We used lanthanide ions (Ln3+) as probes to investigate the Ca2+ sensors of RyR, because they specifically bind to Ca2+-binding proteins and they are impermeable to the channel. Eu3+'s and Sm3+'s action was tested on single RyR1 channels reconstituted into planar lipid bilayers. When the activating binding site was saturated by 50 μM Ca2+, Ln3+ potently inhibited RyR's open probability (Kd Eu3+ = 167 ± 5 nM and Kd Sm3+ = 63 ± 3 nM), but in nominally 0 [Ca2+], low [Eu3+] activated the channel. These results suggest that Ln3+ acts as an agonist of both Ca2+-binding sites. More importantly, the voltage-dependent characteristics of Ln3+'s action led to the conclusion that the activating Ca2+ binding site is located within the electrical field of the channel (in the vestibule). This idea was tested by applying the pore blocker toxin maurocalcine on the cytoplasmic side of RyR. These experiments showed that RyR lost reactivity to changing cytosolic [Ca2+] from 50 μM to 100 nM when the toxin occupied the vestibule. These results suggest that maurocalcine mechanically prevented Ca2+ from dissociating from its binding site and support our vestibular Ca2+ sensor-model further.

Original languageEnglish
Pages (from-to)2127-2137
Number of pages11
JournalBiophysical Journal
Volume112
Issue number10
DOIs
Publication statusPublished - May 23 2017

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Lanthanoid Series Elements
Ryanodine Receptor Calcium Release Channel
Calcium
Binding Sites
Malignant Hyperthermia
Lipid Bilayers
Carrier Proteins
Heart Failure
Ions
Pathology

ASJC Scopus subject areas

  • Biophysics

Cite this

Lanthanides Report Calcium Sensor in the Vestibule of Ryanodine Receptor. / Sárközi, Sándor; Komáromi, I.; Jóna, I.; Almássy, János.

In: Biophysical Journal, Vol. 112, No. 10, 23.05.2017, p. 2127-2137.

Research output: Contribution to journalArticle

Sárközi, Sándor ; Komáromi, I. ; Jóna, I. ; Almássy, János. / Lanthanides Report Calcium Sensor in the Vestibule of Ryanodine Receptor. In: Biophysical Journal. 2017 ; Vol. 112, No. 10. pp. 2127-2137.
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