The calcium release channel of sarcoplasmic reticulum is modulated by FK-506-binding protein. Dissociation and reconstitution of FKBP-12 to the calcium release channel of skeletal muscle sarcoplasmic reticulum.
The ryanodine receptor/calcium release channel (CRC) of rabbit skeletal muscle terminal cisternae (TC) of sarcoplasmic reticulum (SR) has been found to be tightly associated with FK-506 binding protein (FKBP-12), the cytosolic receptor (immunophilin) for the immunosuppressant drug FK-506 (Jayaraman, T., Brillantes, A. M., Timerman, A. P., Fleischer, S., Erdjument-Bromage, H., Tempst, P., and Marks, A. (1992) J. Biol. Chem. 267, 9474-9477). In this study, a procedure is described to dissociate FKBP from TC and reconstitute human recombinant FKBP-12 back to the ryanodine receptor so that the role of the immunophilin on CRC activity can be assessed. Titration of TC vesicles with FK-506 dissociates FKBP from the ryanodine receptor. Sedimentation of FK-506-treated vesicles effectively separates the TC from the soluble FKBP-FK506 complex which remains in the supernatant. The FKBP-deficient TC vesicles have altered functional characteristics: 1) the ATP-stimulated calcium uptake rate of TC vesicles is reduced 2-fold; and 2) the threshold concentration of caffeine required to induce calcium release from TC vesicles is decreased. These changes appear to reflect modification of the calcium release channel since: 1) severalfold higher concentrations of FK-506 do not alter the calcium uptake rate of either longitudinal tubules of SR, or TC vesicles in the presence of ruthenium red; 2) human recombinant FKBP reassociates with FKBP-deficient TC but not with control TC or longitudinal tubules of SR; and 3) the reduced Ca2+ uptake rate in FKBP-deficient TC is restored to control values in the FKBP-reconstituted TC. These studies demonstrate that FKBP-12 modulates the CRC of rabbit skeletal muscle sarcoplasmic reticulum.
Timerman
A P
AP
Department of Molecular Biology, Vanderbilt University, Nashville Tennessee 37235.
Ogunbumni
E
E
Freund
E
E
Wiederrecht
G
G
Marks
A R
AR
Fleischer
S
S
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects; D009124:Muscle Proteins / Q000378:metabolism*; D011485:Protein Binding; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D016559:Tacrolimus / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D022021:Tacrolimus Binding Proteins
D015220:Calcium Channels; D002352:Carrier Proteins; D006360:Heat-Shock Proteins; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D022021:Tacrolimus Binding Proteins; D002118:Calcium; D016559:Tacrolimus