The Anthracycline Metabolite Doxorubicinol Abolishes RyR2 Sensitivity to Physiological Changes in Luminal Ca²⁺through an Interaction with Calsequestrin

Abstract

The chemotherapeutic anthracycline metabolite doxorubicinol (doxOL) has been shown to interact with and disrupt the function of the cardiac ryanodine receptor Ca release channel (RyR2) in the sarcoplasmic reticulum (SR) membrane and the SR Ca binding protein calsequestrin 2 (CSQ2). Normal increases in RyR2 activity in response to increasing diastolic SR [Ca] are influenced by CSQ2 and are disrupted in arrhythmic conditions. Therefore, we explored the action of doxOL on RyR2's response to changes in luminal [Ca] seen during diastole. DoxOL abolished the increase in RyR2 activity when luminal Ca was increased from 0.1 to 1.5 mM. This was not due to RyR2 oxidation, but depended entirely on the presence of CSQ2 in the RyR2 complex. DoxOL binding to CSQ2 reduced both the Ca binding capacity of CSQ2 (by 48%-58%) and its aggregation, and lowered CSQ2 association with the RyR2 complex by 67%-77%. Each of these effects on CSQ2, and the lost RyR2 response to changes in luminal [Ca], was duplicated by exposing native RyR2 channels to subphysiologic (≤1.0 µM) luminal [Ca]. We suggest that doxOL and low luminal Ca both disrupt the CSQ2 polymer, and that the association of the monomeric protein with the RyR2 complex shifts the increase in RyR2 activity with increasing luminal [Ca] away from the physiologic [Ca] range. Subsequently, these changes may render the channel insensitive to changes of luminal Ca that occur through the cardiac cycle. The altered interactions between CSQ2, triadin, and/or junctin and RyR2 may produce an arrhythmogenic substrate in anthracycline-induced cardiotoxicity.

Progression of excitation-contraction coupling defects in doxorubicin cardiotoxicity

“…an initial reversible open probability increase, which might contribute to the elevated Ca 2+ sparks rate, following by its inhibition. In addition, recent data have also shown that the anthracycline metabolite doxorubicinol abolishes the RyR2 sensitivity to luminal Ca 2+ by interacting with cardiac calsequestrin (CSQ2) favoring arrhythmic conditions [20]. While the Reactive Oxygen Species (ROS) effect might be prevented by antioxidants, the direct effect on RyR2 could not [21,22].…”

Weighted gene co-expression network-based approach to identify key genes associated with anthracycline-induced cardiotoxicity and construction of miRNA-transcription factor-gene regulatory network

“…Consistent with our finding, previous studies have demonstrated the important role of Ryr2 in AIC(Pessah, 1992 ; Takaseya et al 2004 ). Doxorubicin could induce calcium release of sarcoplasmic reticulum to induce AIC by directly binding to the cardiac-type ryanodine receptor to inhibit the activity of Ryr2 (Hanna et al 2017 ; Saeki et al 2002 ). These findings along with our results suggest that the regulation of Ryr2 expression or activity may be a potential strategy for the treatment of AIC.…”

Dantrolene sodium increases calcium binding by human recombinant cardiac calsequestrin and calcium loading by sheep cardiac sarcoplasmic reticulum

“…Since drugs such as doxorubicin, which binds to CASQ2 with high affinity and causes a decrease in Ca 2+ binding and CASQ2 polymerization are cardiotoxic, it may be possible that DaNa could oppose this effect, in which case DaNa may act as a cardio‐protective agent to ameliorate such drug‐induced cardiac dysfunction.…”