S100A1 Binds to the Calmodulin-binding Site of Ryanodine Receptor and Modulates Skeletal Muscle Excitation-Contraction Coupling

Abstract

S100A1, a 21-kDa dimeric Ca 2؉-binding protein, is an enhancer of cardiac Ca 2؉ release and contractility and a potential therapeutic agent for the treatment of cardiomyopathy. The role of S100A1 in skeletal muscle has been less well defined. Additionally, the precise molecular mechanism underlying S100A1 modulation of sarcoplasmic reticulum Ca 2؉ release in striated muscle has not been fully elucidated. Here, utilizing a genetic approach to knock out S100A1, we demonstrate a direct physiological role of S100A1 in excitation-contraction coupling in skeletal muscle. We show that the absence of S100A1 leads to decreased global myoplasmic Ca 2؉ transients following electrical excitation. Using high speed confocal microscopy, we demonstrate with high temporal resolution depressed activation of sarcoplasmic reticulum Ca 2؉ release in S100A1 ؊/؊ muscle fibers. Through competition assays with sarcoplasmic reticulum vesicles and through tryptophan fluorescence experiments, we also identify a novel S100A1-binding site on the cytoplasmic face of the intact ryanodine receptor that is conserved throughout striated muscle and corresponds to a previously identified calmodulin-binding site. Using a 12-mer peptide of this putative binding domain, we demonstrate low micromolar binding affinity to S100A1. NMR spectroscopy reveals this peptide binds within the Ca 2؉ -dependent hydrophobic pocket of S100A1. Taken together, these data suggest that S100A1 plays a significant role in skeletal muscle excitation-contraction coupling, primarily through specific interactions with a conserved binding domain of the ryanodine receptor. This warrants further investigation into the use of S100A1 as a therapeutic target for the treatment of both cardiac and skeletal myopathies.The S100 family of proteins, so named because of their solubility in 100% ammonium sulfate, are small (16 -26 kDa), acidic, Ca 2ϩ

El acoplamiento excitación-contracción en el músculo esquelético: preguntas por responder a pesar de 50 años de estudio

“…Son homotetrámeros de alto peso molecular (~560 kDa) con un gran dominio citoplásmico y uno transmembrana que permite el funcionamiento de la proteína como un canal de Ca 2+ que regula la salida de este ión del retículo endoplásmico hacia el citoplasma (21)(22)(23)(24). Su actividad es regulada por el trifosfato de adenosina (ATP), magnesio (Mg 2+ ), Ca 2+ , el estado de oxido-reducción, el estado de fosforilación/desfosforilación y varias proteínas como la calsecuestrina, la calmodulina, la S100A1, la FKBP (FK 506 binding protein) y, posiblemente, por la proteína recién caracterizada SRP-27 (11,21,(25)(26)(27)(28)(29).…”

Skeletal muscle fatigue – regulation of excitation–contraction coupling to avoid metabolic catastrophe

“…One of the important ligands for RyR is S100A1. Prosser and colleagues used a knockout mouse (S100A1) to demonstrate that S100A1 enhances Ca 2+ release (Prosser et al, 2008). Twitch and tetanic contractile amplitudes are attenuated, and the corresponding Ca 2+ transients are smaller in the S100A1 mice compared with muscles of wildtype control mice.…”

S100A1 and Calmodulin Compete for the Same Binding Site on Ryanodine Receptor

“…Recently, several studies demonstrated that an S100 protein, S100A1, enhances RyR1-and RyR2-dependent calcium release in both skeletal and cardiac muscle, respectively (5-10). Specifically, S100A1 knock-out skeletal muscle fibers demonstrate decreased Ca 2ϩ transients (6), and adenoviral delivery of S100A1 into failing cardiomyocytes restores myocyte contractile properties (11). Additionally, S100A1 increases [ 3 H]ryanodine binding to RyR1, indicative of increased activation of the channel (5), and S100A1 binds directly to RyR1 in a calciumdependent manner (6).…”

“…Additionally, S100A1 increases [ 3 H]ryanodine binding to RyR1, indicative of increased activation of the channel (5), and S100A1 binds directly to RyR1 in a calciumdependent manner (6). These data suggest a possible therapeutic role of S100A1 in treatment strategies for skeletal and cardiomyopathies (6,8,11). S100A1 is a symmetric homodimer (93 residues/subunit) with each S100A1 subunit having a low affinity pseudo-EF hand and a second high affinity canonical EF hand calcium binding domain (12).…”