Hypernitrosylated ryanodine receptor calcium release channels are leaky in dystrophic muscle

Abstract

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle weakness and early death resulting from dystrophin deficiency. Loss of dystrophin results in disruption of a large dystrophin glycoprotein complex (DGC) leading to pathologic calcium (Ca2+)-dependent signals that damage muscle cells 1–5. We have identified a structural and functional defect in the sarcoplasmic reticulum (SR) Ca2+ release channel/ryanodine receptor (RyR1) in the mdx mouse model of muscular dystrophy that may contribute to altered Ca2+ homeostasis in dystrophic muscles. RyR1 isolated from mdx skeletal muscle exhibited an age-dependent increase in S-nitrosylation coincident with dystrophic changes in the muscle. RyR1 S-nitrosylation depleted the channel complex of FKBP12 (or “calstabin1” for calcium channel stabilizing binding protein) resulting in “leaky” channels. Preventing calstabin1 depletion from RyR1 using S107, a compound that binds to the RyR1 channel and enhances the binding affinity of calstabin1 to the nitrosylated channel, inhibited SR Ca2+ leak, reduced biochemical and histologic evidence of muscle damage, improved muscle function and increased exercise performance in mdx mice. Thus, SR Ca2+ leak via RyR1 due to S-nitrosylation of the channel and calstabin1 depletion likely contributes to muscle weakness in muscular dystrophy and preventing the RyR1-mediated SR Ca2+ leak may provide a novel therapeutic approach.

nNOS regulation of skeletal muscle fatigue and exercise performance

“…The remodeling of the RyR1 macromolecular complex in mdx muscle was similar to that observed in over-trained muscle (Bellinger et al 2008(Bellinger et al , 2009. Pharmacological stabilization of the RyR1 channel with S107 increased FKBP12 association and reduced Ca 2+ spark frequency to wild-type levels, which decreased calpain-mediated muscle damage and enhanced fatigue resistance (Bellinger et al 2009). Interestingly, the RyR1 leak may lead to excessive nNOS activation and RyR1 hypernitrosylation, leading to even more Ca 2+ leak and progressive muscle damage and weakness (Durham et al 2008, Figure 1).…”

“…nNOSμ depletion restored RyR1 nitrosylation to basal levels and enhanced muscle strength (Li et al 2011a), suggesting that aberrant activation of cytosolic nNOSμ was leading to excessive nitrosylation of RyR1 and, consequently, suppressing muscle strength. RyR1 hypernitrosylation was also observed in mdx mice (Bellinger et al 2009). Increased RyR1 nitrosylation led to reduced FKBP12 association, promoting the RyR1 channel Ca 2+ leak (Bellinger et al 2009).…”

“…RyR1 hypernitrosylation was also observed in mdx mice (Bellinger et al 2009). Increased RyR1 nitrosylation led to reduced FKBP12 association, promoting the RyR1 channel Ca 2+ leak (Bellinger et al 2009). The remodeling of the RyR1 macromolecular complex in mdx muscle was similar to that observed in over-trained muscle (Bellinger et al 2008(Bellinger et al , 2009.…”

“…nNOSμ-mediated RyR1 hypernitrosylation was observed in mdx mice and correlated with muscle weakness (Bellinger et al 2009;Li et al 2011a;Li et al 2011b). nNOSμ depletion restored RyR1 nitrosylation to basal levels and enhanced muscle strength (Li et al 2011a), suggesting that aberrant activation of cytosolic nNOSμ was leading to excessive nitrosylation of RyR1 and, consequently, suppressing muscle strength.…”

“…Increased RyR1 nitrosylation led to reduced FKBP12 association, promoting the RyR1 channel Ca 2+ leak (Bellinger et al 2009). The remodeling of the RyR1 macromolecular complex in mdx muscle was similar to that observed in over-trained muscle (Bellinger et al 2008(Bellinger et al , 2009. Pharmacological stabilization of the RyR1 channel with S107 increased FKBP12 association and reduced Ca 2+ spark frequency to wild-type levels, which decreased calpain-mediated muscle damage and enhanced fatigue resistance (Bellinger et al 2009).…”