Ryanodine receptor type-1 (RyR1) expression and protein S-nitrosylation pattern in human soleus myofibres following bed rest and exercise countermeasure

The ryanodine receptor type-I (RyR1) is one key player of the excitation-contraction coupling (E-CC) machinery. However, RyR1 expression in human skeletal muscle disuse and plasticity changes are not well documented. We studied the expression and the functional modifications of RyR1 following prolonged bed rest (BR) without and with exercise countermeasure (Resistive Vibration Exercise, RVE). Soleus biopsies were taken from a non- trained control (BR-CTRL) and trained (BR-RVE) group (each n = 10) before and after BR. In BR-CTRL group, a fibre type-specific immunopattern of RyR1 (type-I < type-II) was documented, and RyR1 immunofluorescence intensity and protein expression together with [H-3] ryanodine binding were decreased after BR. In BR-RVE group, RyR1 immunosignals were increased and fiber type specificity was no longer present. RyR1 protein expression was unchanged, whereas [3H] ryanodine binding increased after BR. Confocal and biochemical analysis confirmed subcellular co-localisation and protein-protein interaction of RyR1 with nitric oxide (NO)-synthase type-1 ( NOS1). S-nitrosylation of RyR1 was increased in BR-CTRLpost only, suggesting a reduction of RyR1 open channel probability by nitrosylation mechanisms following prolonged disuse. We conclude that following extended body deconditioning in bed rest, RVE countermeasure maintained normal RyR1 expression and nitrosylation patterns required for adequate E-CC in human performance control.