title: Ryanodine receptors from rabbit skeletal muscle are reversibly activated by rapamycin.
abstract: In this report we demonstrate that the immunosuppressive drug, rapamycin, can reversibly activate the skeletal muscle ryanodine receptor calcium release channel (RyR) in terminal cisternae vesicles incorporated into planar lipid bilayers. This reveals a second mechanism of activation of RyRs by rapamycin. Irreversible channel activation and openings to subconductance levels are seen when rapamycin forms a complex with and removes the tightly bound 12 kDa FK506-binding protein (FKBP12) from the RyR. We show here that micromolar rapamycin activates RyRs which were previously 'stripped' of > 95% of their FKBP12s. Rapamycin caused a 6-fold increase in mean current, which was largely reversible, but no increase in the fraction of openings to subconductance levels. Therefore native RyRs, stripped of FKBP12, are directly activated by the macrocyclic lactone, rapamycin.
authors.affiliation: Membrane Biology Program, John Curtin School of Medical Research, Australian National University, Canberra, Australia.
authors.forename: G P
authors.initials: GP
authors.lastname: Ahern
authors.forename: P R
authors.initials: PR
authors.lastname: Junankar
authors.forename: A F
authors.initials: AF
authors.lastname: Dulhunty
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D009124:Muscle Proteins / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects*; D011090:Polyenes / Q000494:pharmacology*; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel; D020123:Sirolimus
chemical_list: D015220:Calcium Channels; D007166:Immunosuppressive Agents; D009124:Muscle Proteins; D011090:Polyenes; D019837:Ryanodine Receptor Calcium Release Channel; D020123:Sirolimus