Key Points
- To determine whether FKBP12 selectively associates with skeletal muscle ryanodine receptor type 1 (RyR1) compared to other ryanodine receptor isoforms, inositol 1,4,5-trisphosphate receptor isoforms, and calcineurin across tissues.
- Measured endogenous FKBP12 association and FK506-mediated displacement in microsomes isolated from brain, skeletal muscle, and cardiac tissue.
- Assayed binding affinity of an FKBP12-glutathione-S-transferase (GST) fusion protein to solubilized microsomal channel proteins across each tissue.
- FKBP12 showed a tight, high-affinity association with skeletal muscle microsomes that was displaced by FK506, but it lacked tight association with brain or cardiac microsomes.
- Among solubilized microsomal proteins, only skeletal muscle RyR1 bound to the FKBP12-GST fusion protein in a high-affinity, FK506-displaceable manner, unlike RyR2, RyR3, IP3 receptors, or calcineurin.
Structured PICO
PPopulationBrain, skeletal muscle, and cardiac tissue microsomes
IInterventionFK506 displacement and FKBP12-glutathione-S-transferase fusion protein binding assay
OOutcomeRelative levels of ryanodine receptor (RyR) isoforms, IP3R isoforms, and calcineurin, and their association with FKBP12surrogate
Skeletal muscle RyR1 has distinctive, high-affinity FKBP12 binding properties compared to cardiac RyR2, brain RyR3, IP3 receptors, and calcineurin.