title: Asymmetrical blockade of the Ca2+ release channel (ryanodine receptor) by 12-kDa FK506 binding protein.
abstract: A soluble 12-kDa FK506 binding protein (FKBP12), the cellular receptor of the immunosuppressive drug FK506, is tightly associated with the Ca2+ release channel of rabbit skeletal muscle sarcoplasmic reticulum [Jayaraman, T., Brillantes, A. M., Timerman, A. P., Fleischer, S., Erdjument-Bromage, H., Tempst, P. & Marks, A. (1992) J. Biol. Chem. 267, 9474-9477]. We have assessed the role of excess free FKBP12 in the function of single Ca2+ release channels incorporated into planar lipid bilayers. The addition of human recombinant FKBP12 (hFKBP12) to the cytoplasmic face of the Ca2+ release channel blocked the flow of cytoplasmic to luminal current (outward current) in a concentration-dependent manner but had no significant effect on the flow of luminal to cytoplasmic current (inward current). The luminal to cytoplasmic flow of current was modulated by Ca2+, Mg2+, ATP, caffeine, and ryanodine in the presence and absence of FKBP12. An immunosuppressive drug, L-683,590, an analog of FK506, did not block or reverse the asymmetrical hFKBP12 blockade of single Ca2+ release channels in planar lipid bilayers. FKBP12 may play a role in regulation of the flow of ions into the lumen of the sarcoplasmic reticulum through the Ca2+ release channel.
authors.affiliation: Banting and Best Department of Medical Research, University of Toronto, Charles H. Best Institute, ON Canada.
authors.forename: S R
authors.initials: SR
authors.lastname: Chen
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.forename: D H
authors.initials: DH
authors.lastname: MacLennan
mesh_terms: D000818:Animals; D001483:Base Sequence; D015220:Calcium Channels / Q000502:physiology*; D002352:Carrier Proteins / Q000096:biosynthesis / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000494:pharmacology*; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000494:pharmacology*; D006801:Humans; D007106:Immune Sera; D007700:Kinetics; D008051:Lipid Bilayers; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009124:Muscle Proteins / Q000502:physiology*; D009132:Muscles / Q000502:physiology; D016133:Polymerase Chain Reaction; D011817:Rabbits; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000494:pharmacology; D015183:Restriction Mapping; D019837:Ryanodine Receptor Calcium Release Channel; D012519:Sarcoplasmic Reticulum / Q000502:physiology*; D016559:Tacrolimus / Q000494:pharmacology; D022021:Tacrolimus Binding Proteins; D013997:Time Factors
chemical_list: D015220:Calcium Channels; D002352:Carrier Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D007106:Immune Sera; D008051:Lipid Bilayers; D009124:Muscle Proteins; D011994:Recombinant Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D022021:Tacrolimus Binding Proteins; D016559:Tacrolimus