Ryanodine receptor allosteric coupling and the dynamics of calcium sparks. 2008

Jeffrey R Groff, and Gregory D Smith
Department of Applied Science, College of William and Mary, Williamsburg, Virginia, USA.

Puffs and sparks are localized intracellular Ca(2+) elevations that arise from the cooperative activity of Ca(2+)-regulated inositol 1,4,5-trisphosphate receptors and ryanodine receptors clustered at Ca(2+) release sites on the surface of the endoplasmic reticulum or the sarcoplasmic reticulum. While the synchronous gating of Ca(2+)-regulated Ca(2+) channels can be mediated entirely though the buffered diffusion of intracellular Ca(2+), interprotein allosteric interactions also contribute to the dynamics of ryanodine receptor (RyR) gating and Ca(2+) sparks. In this article, Markov chain models of Ca(2+) release sites are used to investigate how the statistics of Ca(2+) spark generation and termination are related to the coupling of RyRs via local [Ca(2+)] changes and allosteric interactions. Allosteric interactions are included in a manner that promotes the synchronous gating of channels by stabilizing neighboring closed-closed and/or open-open channel pairs. When the strength of Ca(2+)-mediated channel coupling is systematically varied (e.g., by changing the Ca(2+) buffer concentration), simulations that include synchronizing allosteric interactions often exhibit more robust Ca(2+) sparks; however, for some Ca(2+) coupling strengths the sparks are less robust. We find no evidence that the distribution of spark durations can be used to distinguish between allosteric interactions that stabilize closed channel pairs, open channel pairs, or both in a balanced fashion. On the other hand, the changes in spark duration, interspark interval, and frequency observed when allosteric interactions that stabilize closed channel pairs are gradually removed from simulations are qualitatively different than the changes observed when open or both closed and open channel pairs are stabilized. Thus, our simulations clarify how changes in spark statistics due to pharmacological washout of the accessory proteins mediating allosteric coupling may indicate the type of synchronizing allosteric interactions exhibited by physically coupled RyRs. We also investigate the validity of a mean-field reduction applicable to the dynamics of a ryanodine receptor cluster coupled via local [Ca(2+)] and allosteric interactions. In addition to facilitating parameter studies of the effect of allosteric coupling on spark statistics, the derivation of the mean-field model establishes the correct functional form for cooperativity factors representing the coupled gating of RyRs. This mean-field formulation is well suited for use in computationally efficient whole cell simulations of excitation-contraction coupling.

UI MeSH Term Description Entries
D008956 Models, Chemical Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment. Chemical Models,Chemical Model,Model, Chemical
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002462 Cell Membrane The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells. Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D003198 Computer Simulation Computer-based representation of physical systems and phenomena such as chemical processes. Computational Modeling,Computational Modelling,Computer Models,In silico Modeling,In silico Models,In silico Simulation,Models, Computer,Computerized Models,Computer Model,Computer Simulations,Computerized Model,In silico Model,Model, Computer,Model, Computerized,Model, In silico,Modeling, Computational,Modeling, In silico,Modelling, Computational,Simulation, Computer,Simulation, In silico,Simulations, Computer
D015640 Ion Channel Gating The opening and closing of ion channels due to a stimulus. The stimulus can be a change in membrane potential (voltage-gated), drugs or chemical transmitters (ligand-gated), or a mechanical deformation. Gating is thought to involve conformational changes of the ion channel which alters selective permeability. Gating, Ion Channel,Gatings, Ion Channel,Ion Channel Gatings
D019837 Ryanodine Receptor Calcium Release Channel A tetrameric calcium release channel in the SARCOPLASMIC RETICULUM membrane of SMOOTH MUSCLE CELLS, acting oppositely to SARCOPLASMIC RETICULUM CALCIUM-TRANSPORTING ATPASES. It is important in skeletal and cardiac excitation-contraction coupling and studied by using RYANODINE. Abnormalities are implicated in CARDIAC ARRHYTHMIAS and MUSCULAR DISEASES. Calcium-Ryanodine Receptor Complex,RyR1,Ryanodine Receptor 1,Ryanodine Receptor 2,Ryanodine Receptor 3,Ryanodine Receptors,Ca Release Channel-Ryanodine Receptor,Receptor, Ryanodine,RyR2,RyR3,Ryanodine Receptor,Ca Release Channel Ryanodine Receptor,Calcium Ryanodine Receptor Complex,Complex, Calcium-Ryanodine Receptor,Receptor 1, Ryanodine,Receptor 2, Ryanodine,Receptor 3, Ryanodine,Receptor Complex, Calcium-Ryanodine,Receptors, Ryanodine
D020013 Calcium Signaling Signal transduction mechanisms whereby calcium mobilization (from outside the cell or from intracellular storage pools) to the cytoplasm is triggered by external stimuli. Calcium signals are often seen to propagate as waves, oscillations, spikes, sparks, or puffs. The calcium acts as an intracellular messenger by activating calcium-responsive proteins. Calcium Oscillations,Calcium Waves,Calcium Puffs,Calcium Sparks,Calcium Spikes,Calcium Oscillation,Calcium Puff,Calcium Signalings,Calcium Spark,Calcium Spike,Calcium Wave,Oscillation, Calcium,Oscillations, Calcium,Puff, Calcium,Puffs, Calcium,Signaling, Calcium,Signalings, Calcium,Spark, Calcium,Sparks, Calcium,Spike, Calcium,Spikes, Calcium,Wave, Calcium,Waves, Calcium

Related Publications

Jeffrey R Groff, and Gregory D Smith
July 2006, Biophysical journal,
Jeffrey R Groff, and Gregory D Smith
June 2005, Journal of molecular biology,
Jeffrey R Groff, and Gregory D Smith
December 2014, Biophysical journal,
Jeffrey R Groff, and Gregory D Smith
September 2011, Biophysical journal,
Jeffrey R Groff, and Gregory D Smith
January 2000, Journal of basic and clinical physiology and pharmacology,
Jeffrey R Groff, and Gregory D Smith
January 2015, Research and reports in biology,
Jeffrey R Groff, and Gregory D Smith
June 1994, Biophysical journal,
Copied contents to your clipboard!