• Tanya R Cully, Rocky H Choi, Andrew R Bjorksten, D George Stephenson, Robyn M Murphy, and Bradley S Launikonis.
• School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, QLD 4072, Australia.
• Proc. Natl. Acad. Sci. U.S.A. 2018 Aug 7; 115 (32): 8215-8220.

AbstractWe used the nanometer-wide tubules of the transverse tubular (t)-system of human skeletal muscle fibers as sensitive sensors for the quantitative monitoring of the Ca2+-handling properties in the narrow junctional cytoplasmic space sandwiched between the tubular membrane and the sarcoplasmic reticulum cisternae in single muscle fibers. The t-system sealed with a Ca2+-sensitive dye trapped in it is sensitive to changes in ryanodine receptor (RyR) Ca2+ leak, the store operated calcium entry flux, plasma membrane Ca pump, and sodium-calcium exchanger activities, thus making the sealed t-system a nanodomain Ca2+ sensor of Ca2+ dynamics in the junctional space. The sensor was used to assess the basal Ca2+-handling properties of human muscle fibers obtained by needle biopsy from control subjects and from people with a malignant hyperthermia (MH) causative RyR variant. Using this approach we show that the muscle fibers from MH-susceptible individuals display leakier RyRs and a greater capacity to extrude Ca2+ across the t-system membrane compared with fibers from controls. This study provides a quantitative way to assess the effect of RyR variants on junctional membrane Ca2+ handling under defined ionic conditions.

34 keywords...

hide…