A Novel FK506 Binding Protein Can Mediate the Immunosuppressive Effects of FK506 and Is Associated with the Cardiac Ryanodine Receptor (*)
- Elsa Lam(1),
- Mary M. Martin(1),
- Anthony P. Timerman(5),
- Candace Sabers(4),
- Sidney Fleischer(5),
- Thomas Lukas(6),
- Robert T. Abraham(4)(3),
- Stephen J. O'Keefe(2),
- Edward A. O'Neill(2) and
- Gregory J. Wiederrecht(1)(§)
- From the (1) Departments of Immunology Research and
- (2) Molecular Immunology, Merck Research Laboratories, Rahway, New Jersey 07065, the Departments of
- (3) Immunology and
- (4) Pharmacology, Mayo Clinic, Rochester, Minnesota 55905, and the Departments of
- (5) Molecular Biology,
- (6) Cell Physiology, and
- (7) Biophysics, Vanderbilt University, Nashville, Tennessee 37235
- § To whom correspondence should be addressed: Merck Research Laboratories, Dept. of Immunology Research, P. O. Box 2000; Mail Code R80W-107, Rahway, NJ 07065. Tel.: 908-594-3211; Fax: 908-594-7926.
Abstract
FK506, an immunosuppressant that prolongs allograft survival, is a co-drug with its intracellular receptor, FKBP12. The FKBP12•FK506 complex inhibits calcineurin, a critical signaling molecule during T-cell activation. FKBP12 was, until recently, the sole FKBP known to mediate calcineurin inhibition at clinically relevant FK506 concentrations. The best characterized cellular function of FKBP12 is the modulation of ryanodine receptor isoform-1, a component of the calcium release channel of skeletal muscle sarcoplasmic reticulum.
Recently, a novel protein, FKBP12.6, was found to inhibit calcineurin at clinically relevant FK506 concentrations. We have cloned the cDNA encoding human FKBP12.6 and characterized the protein. In transfected Jurkat cells, FKBP12.6 is equivalent to FKBP12 at mediating the inhibitory effects of FK506. Upon binding rapamycin, FKBP12.6 complexes with the 288-kDa mammalian target of rapamycin. In contrast to FKBP12, FKBP12.6 is not associated with ryanodine receptor isoform-1 but with the distinct ryanodine receptor isoform-2 in cardiac muscle sarcoplasmic reticulum. Our results suggest that FKBP12.6 has both a unique physiological role in excitation-contraction coupling in cardiac muscle and the potential to contribute to the immunosuppressive and toxic effects of FK506 and rapamycin.
Footnotes
-
↵* This work was funded in part by a grant, IM-751, from the American Cancer Society (to R. A.) and National Institutes of Health Grants HL32711, PO1-HL46681 (to S. F.), and GM30861 (to D. M. W.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank(TM)/EMBL Data Bank with accession number(s) L37086[GenBank].
-
↵1 The abbreviations used are:
- RAP
-
rapamycin
- CaN
-
calcineurin
- FKBP
-
FK506 binding protein
- ‘818
-
L-685,818
- mTOR
-
mammalian target of rapamycin
- SR
-
sarcoplasmic reticulum
- TC
-
terminal cisternae
- RyR
-
ryanodine receptor
- CRC
-
calcium release channel
- PCR
-
polymerase chain reaction
- ORF
-
open reading frame
- RACE
-
rapid amplification of cDNA ends
- IL
-
interleukin
- CHAPS
-
3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid
- ‘590
-
L-683,590
- PAGE
-
polyacrylamide gel electrophoresis
- TEMED
-
N,N,N‘,N‘-tetramethyethyenediamine
- CyP
-
cyclophilin
- GST
-
glutathione S-transferase
- CsA
-
cyclosporin A.
-
↵2 A. P. Timerman, H. Onoue, H.-B. Xin, S. Barg, G. Wiederrecht, and S. Fleischer, submitted for publication.
-
- Received May 16, 1995.
- Revision received August 11, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
