FK-506, a potent novel immunosuppressive agent, binds to a cytosolic protein which is distinct from the cyclosporin A-binding protein, cyclophilin

J. J. Siekierka, M. J. Staruch, S. H.Y. Hung, N. H. Sigal

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Abstract

A novel macrolide antibiotic, FK-506, isolated from Streptomyces tsukubaensis, has been shown to be a potent immunosuppressive agent in vivo and in vitro. FK-506 shares a number of immunosuppressive properties with the cyclic peptide, cyclosporin A (CsA), although 10 to 100 times more potent in this regard. These similarities suggest that both agents may share a similar mechanism(s) of action at the biochemical level. We have identified a cytoplasmic binding protein for FK-506 in the human T cell line, JURKAT, using [3H]FK-506. The FK-506 binding protein has a m(R), of 10 to 12 kDa (as determined by gel filtration), is heat stable and does not bind CsA. This contrasts with the CsA binding protein, cyclophilin, in that cyclophilin is heat labile and has a m(R), of 15 to 17 kDa. Our data suggest that FK-506 binds to a low m.w. protein(s) in JURKAT cells, which is distinct from cyclophilin. This protein may mediate the immunosuppressive effects of FK-506 in T cells. In addition, our results suggest that the immunosuppressive activity of FK-506, as with CsA, is mediated by an intracellular mechanism.

Original languageEnglish
Pages (from-to)1580-1583
Number of pages4
JournalJournal of Immunology
Volume143
Issue number5
StatePublished - 1 Jan 1989

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