title: Insights into the gating mechanism of the ryanodine-modified human cardiac Ca2+-release channel (ryanodine receptor 2).
abstract: Ryanodine receptors (RyRs) are intracellular membrane channels playing key roles in many Ca(2+) signaling pathways and, as such, are emerging novel therapeutic and insecticidal targets. RyRs are so named because they bind the plant alkaloid ryanodine with high affinity and although it is established that ryanodine produces profound changes in all aspects of function, our understanding of the mechanisms underlying altered gating is minimal. We address this issue using detailed single-channel gating analysis, mathematical modeling, and energetic evaluation of state transitions establishing that, with ryanodine bound, the RyR pore adopts an extremely stable open conformation. We demonstrate that stability of this state is influenced by interaction of divalent cations with both activating and inhibitory cytosolic sites and, in the absence of activating Ca(2+), trans-membrane voltage. Comparison of the conformational stability of ryanodine- and Imperatoxin A-modified channels identifies significant differences in the mechanisms of action of these qualitatively similar ligands.
authors.affiliation: Institute of Molecular and Experimental Medicine, Wales Heart Research Institute, Cardiff University School of Medicine, Heath Park, Cardiff, United Kingdom.
authors.forename: Saptarshi
authors.initials: S
authors.lastname: Mukherjee
authors.affiliation: Institute of Molecular and Experimental Medicine, Wales Heart Research Institute, Cardiff University School of Medicine, Heath Park, Cardiff, United Kingdom.
authors.forename: N Lowri
authors.initials: NL
authors.lastname: Thomas
authors.affiliation: Institute of Molecular and Experimental Medicine, Wales Heart Research Institute, Cardiff University School of Medicine, Heath Park, Cardiff, United Kingdom williamsaj9@cardiff.ac.uk.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Williams
mesh_terms: D002118:Calcium / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating; D007700:Kinetics; D008954:Models, Biological; D011487:Protein Conformation; D012433:Ryanodine / Q000737:chemistry; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000502:physiology*; D012604:Scorpion Venoms / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D012604:Scorpion Venoms; C105361:imperatoxin A; D012433:Ryanodine; D002118:Calcium