Immunophilin Modulation of Calcium Channel Gating
1Cardiovascular Institute, Mount Sinai School of Medicine, New York, New York, 10029
Methods (San Diego, Calif.)
|April 1, 1996
Summary
FKBP12 modulates calcium release channels (RyR) by altering gating properties, independent of FK506 or rapamycin. This reveals FKBP12
Area of Science:
- Molecular biology
- Cellular physiology
- Biophysics
Background:
- FKBP12 is a receptor for immunosuppressants FK506 and rapamycin.
- FKBP12 was previously shown to copurify with the ryanodine receptor (RyR).
Purpose of the Study:
- To determine the cellular function of FKBP12.
- To investigate FKBP12's role in modulating calcium release channel activity.
Main Methods:
- Coexpression of RyR and FKBP12 in insect cells.
- Reconstitution of the RyR-FKBP complex into planar lipid bilayers.
- Single-channel recording and analysis.
- Heterologous expression of RyR1 in Xenopus oocytes.
Main Results:
- FKBP12 modulates RyR channel gating, decreasing subconductance states and open probability while increasing mean open time.
- FK506 and rapamycin reversed FKBP12's effects by inhibiting isomerase activity and dissociating the complex.
- FKBP12 is not essential for RyR tetramer formation or membrane insertion.
Conclusions:
- FKBP12 has a ligand-independent cellular function in modulating calcium release channel activity.
- The functional calcium release channel complex intrinsically includes FKBP12.
- Insect cells and Xenopus oocytes are suitable models for studying FKBP12-RyR interactions.
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