Communicated by Kyriacos C. Nicolaou, The Scripps Research Institute, La Jolla, CA, November 8, 2007 (received for review August 15, 2007)
Rapamycin is an immunosuppressive immunophilin ligand reported as having neurotrophic activity. We show that modification of rapamycin at the mammalian target of rapamycin (mTOR) binding region yields immunophilin ligands, WYE-592 and ILS-920, with potent neurotrophic activities in cortical neuronal cultures, efficacy in a rodent model for ischemic stroke, and significantly reduced immunosuppressive activity. Surprisingly, both compounds showed higher binding selectivity for FKBP52 versus FKBP12, in contrast to previously reported immunophilin ligands. Affinity purification revealed two key binding proteins, the immunophilin FKBP52 and the β1-subunit of L-type voltage-dependent Ca2+ channels (CACNB1). Electrophysiological analysis indicated that both compounds can inhibit L-type Ca2+ channels in rat hippocampal neurons and F-11 dorsal root ganglia (DRG)/neuroblastoma cells. We propose that these immunophilin ligands can protect neurons from Ca2+-induced cell death by modulating Ca2+ channels and promote neurite outgrowth via FKBP52 binding.
Author contributions: B.R. and K.P. contributed equally to the work. B.R., K.P., M.B., M.M.Z., P.H.R., R.L.M., J.S., M.N.P., F.E.K., G.T.C., M.A.-G., and E.I.G. designed research; B.R., K.P., F.J., R.A.C., D.L., S.L., Y.C., M.L.M., X.F., F.B., L.M., and E.I.G. performed research; B.R., K.P., M.B., R.A.C., M.L.M., D.v.S., L.M., M.M.Z., A.W., R.L.M., M.N.P., and E.I.G. analyzed data; and B.R., M.N.P., and E.I.G. wrote the paper.
Conflict of interest statement: All authors are or were employees of Wyeth and currently hold stock options in Wyeth.
This article contains supporting information online at www.pnas.org/cgi/content/full/0710424105/DC1.
