Rose bengal activates the Ca2+ release channel from skeletal muscle sarcoplasmic reticulum

Abstract The photooxidizing xanthene dye rose bengal (10 n m to 1 μ m ) stimulates rapid Ca 2+ release from skeletal muscle sarcoplasmic reticulum vesicles. Following fusion of sarcoplasmic reticulum (SR) vesicles to an artificial bilayer, reconstituted Ca 2+ channel activity is stimulated by nanomolar concentrations of rose bengal in the presence of a broad-spectrum light source. Rose bengal does not appear to affect K + channels present in the SR. Following reconstitution of the sulfhydryl-activated 106-kDa Ca 2+ channel protein into a bilayer, rose bengal activates the isolated protein in a light-dependent manner. Ryanodine at a concentration of 10 n m is shown to lock the 106-kDa channel protein in a subconductance state which can be reversed by subsequent addition of 500 n m rose bengal. This apparent displacement of bound ryanodine by nanomolar concentrations of rose bengal is also directly observed upon measurement of [ 3 H]ryanodine binding to JSR vesicles. These observations indicate that photooxidation of rose bengal causes a stimulation of the Ca 2+ release protein from skeletal muscle sarcoplasmic reticulum by interacting with the ryanodine binding site. Furthermore, similar effects of rose bengal on isolated SR vesicles, on single channel measurements following fusion of SR vesicles, and following incorporation of the isolated 106-kDa protein strongly implicates the 106-kDa sulfhydryl-activated Ca 2+ channel protein in the Ca 2+ release process.