Cysteines 1078 and 2991 cross-linking plays a critical role in redox regulation of cardiac ryanodine receptor (RyR)

Abstract

The most common cardiac pathologies, such as myocardial infarction and heart failure, are associated with oxidative stress. Oxidation of the cardiac ryanodine receptor (RyR2) Ca2+ channel causes spontaneous oscillations of intracellular Ca2+, resulting in contractile dysfunction and arrhythmias. RyR2 oxidation promotes the formation of disulfide bonds between two cysteines on neighboring RyR2 subunits, known as intersubunit cross-linking. However, the large number of cysteines in RyR2 has been a major hurdle in identifying the specific cysteines involved in this pathology-linked post-translational modification of the channel. Through mutagenesis of human RyR2 and in-cell Ca2+ imaging, we identify that only two cysteines (out of 89) in each RyR2 subunit are responsible for half of the channel’s functional response to oxidative stress. Our results identify cysteines 1078 and 2991 as a redox-sensitive pair that forms an intersubunit disulfide bond between neighboring RyR2 subunits during oxidative stress, resulting in a pathological “leaky” RyR2 Ca2+ channel.

Calcium’s Role and Signaling in Aging Muscle, Cellular Senescence, and Mineral Interactions

“…Also, ROS generation has been shown to increase IP3R, RyR, and TRPC channels, which are responsible for Ca 2+ release, and iron regulatory protein 1, which induces more Fe 2+ uptake. This further exacerbates lipid peroxidation, creating a vicious cycle of aggravated oxidative stress by calcium and iron [152,153,162,167,168]. Although it has not been mechanistically examined, Fe 2+ -induced oxidative stress, presumably, is involved in other redox-sensitive Ca 2+ -regulated enzymes such as CaMKII and calcineurin.…”

Mitochondrial Calcium Overload Plays a Causal Role in Oxidative Stress in the Failing Heart

“…Red circle in the diagram indicates the cysteines prone to oxidation for each RyR2 domain according to [ 243 ]. The same applies for the yellow circles, but according to [ 253 ] ( C ) Human RyR2 structure (PDB: 7UA3) showing the top and side views ( left ). The discussed oxidized cysteines are indicated in the close-up views ( right ).…”

“…Nonetheless, through the application of genetic techniques to induce specific truncations and modifications in channel residues and domains, a recent study pinpointed that only two cysteine residues within each RyR2 subunit were accountable for nearly half of RyR2’s functional response when exposed to oxidative stress, specifically cysteine 1078 within the Ry1&2-SPRY2 linker and cysteine 2991 in the BSol loop function as a redox-sensitive pair. They engage in the formation of inter-subunit disulfide cross-links between adjacent subunits when confronted with oxidative stress, ultimately leading to an aberrant RyR2 Ca 2+ leakage [ 253 ]. This finding aligns with the observation of elevated levels of RyR2 cross-linking in ventricular myocytes extracted from failing hearts [ 254 ].…”

“…Additionally, as previously discussed, while the previous research has pointed to cysteine 3635 in RyR1 or its equivalent, cysteine 3602, as the most hyperactive redox-sensitive residue, Nikolaienko et al demonstrated that this particular residue did not contribute to channel cross-linking or the activation of Ca 2+ leakage due to oxidative stress [ 245 , 253 ]. In concordance with previous discoveries, Nikolaienko et al also showed that although none of the cysteine residues in the N-terminal domain (NTD) directly participated in cross-linking, they did play a pivotal role in allosterically supporting inter-subunit cross-linking within RyR2.…”