Abstract
The polyketides FK506 (tacrolimus) and FK520 (ascomycin) are potent immunosuppressants that function by inhibiting calcineurin phosphatase through formation of an FKBP12-FK506/520-calcineurin ternary complex. They also have calcineurin-independent neuroregenerative properties in cell culture and animal models of nervous system disorders. Based on the crystal structure of the FKBP12-FK506-calcineurin complex, we deduced that the 13- and 15-methoxy groups of FK506 or FK520 are important for inhibition of calcineurin phosphatase but not for binding to FKBP12. By genetic modification of the FK520 gene cluster, we generated 13- and 15-desmethoxy analogs of FK520 that contain hydrogen, methyl, or ethyl instead of methoxy at one or both of these positions. These analogs bind FKBP12 tightly, have decreased calcineurin phosphatase inhibition and immunosuppressive properties, and enhance neurite outgrowth in cell cultures. A representative compound was also shown to accelerate nerve regeneration and functional recovery in the rat sciatic nerve crush model.
Footnotes
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↵1 Current address: Gilead Sciences, 333 Lakeside Dr., Foster City, CA 94404.
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This work was supported in part by National Institutes of Health Grant NS-42542-01 to Kosan Biosciences, Inc. B.G.G. is a consultant to and has financial interest in Kosan Biosciences, Inc.
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DOI: 10.1124/jpet.102.034264
- Abbreviations:
- FKBP
- human FK506 binding protein
- PKS
- polyketide synthase
- PCR
- polymerase chain reaction
- LC/MS
- liquid chromatography/mass spectrometry
- XTT
- 2,3-bis[2-methoxy-4-nitro-5-sulfo-phenyl]-2H-tetrazolium-5-carboxyanilide
- XIC
- extracted ion chromatogram
- 13-Me-18-OH FK520
- 13-desmethoxy-13-methyl-18-hydroxy FK520
- NGF
- nerve growth factor
- 13-H-15-H FK520
- 13,15-bis-desmethoxy FK520
- Received February 11, 2002.
- Accepted May 21, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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