Diketopyridylryanodine Has Three Concentration-dependent Effects on the Cardiac Calcium-release Channel/Ryanodine Receptor

By interacting with more than one site, ryanoids induce multiple effects on calcium-release channels. To date, the kinetics of interaction of only one of these sites has been characterized. Using C4,C12-diketopyridylryanodine in both [3H]ryanodine binding and single channel experiments we characteri...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of biological chemistry 2003-04, Vol.278 (16), p.14237-14248
Main Authors: Bidasee, Keshore R., Xu, Le, Meissner, Gerhard, Besch, Henry R.
Format: Article
Language:English
Subjects:
Algorithms
Animals
Binding Sites
Calcium - metabolism
diketopyridylryanodine
Dogs
Dose-Response Relationship, Drug
Inhibitory Concentration 50
Kinetics
Ligands
Models, Chemical
Models, Molecular
Myocardium - metabolism
Protein Binding
Ryanodine - analogs & derivatives
Ryanodine - chemistry
Ryanodine - metabolism
Ryanodine - pharmacology
Ryanodine Receptor Calcium Release Channel - metabolism
Sarcoplasmic Reticulum - metabolism
Time Factors
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:By interacting with more than one site, ryanoids induce multiple effects on calcium-release channels. To date, the kinetics of interaction of only one of these sites has been characterized. Using C4,C12-diketopyridylryanodine in both [3H]ryanodine binding and single channel experiments we characterized another site on the cardiac ryanodine receptor (RyR2) with which ryanoids interact. Competitive binding of this ryanoid to RyR2 implied a minimal two-site binding model. At the single channel level, C4,C12-diketopyridylryanodine induced three distinct effects. At nanomolar concentrations, it increased channel open probability severalfold without inducing a subconductance. This effect was independent of membrane holding potential. As for other ryanoids, low micromolar concentrations of C4,C12-diketopyridylryanodine readily induced a subconductance state. The major subconductance had a current amplitude of 52% of fully open, it was reversible, and its time to induction and duration were voltage- and concentration-dependent, affording Hill slopes of >2. At higher micromolar concentrations C4,C12-diketopyridylryanodine induced long lasting, yet reversible shut states. Using a pharmacological strategy we have discerned an additional ryanoid-binding site on RyR2 that triggers an increase in channel activity. This site likely resides outside the strict confines of the transmembrane conducting pathway.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M208372200