Preclinical Characterization of Naturally Occurring Polyketide Cyclophilin Inhibitors from the Sanglifehrin Family
Matthew A. GregoryMichael BobardtSusan ObeidUdayan ChatterjiNigel J. CoatesTeresa A. FosterPhilippe GallayPieter LeyssenSteven J. MossJohan NeytsMohammad Nur‐e‐AlamJan PaeshuyseMahmood PiraeeDipen SutharTony WarneckMing‐Qiang ZhangBarrie Wilkinson
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ABSTRACT Cyclophilin inhibitors currently in clinical trials for hepatitis C virus (HCV) are all analogues of cyclosporine (CsA). Sanglifehrins are a group of naturally occurring cyclophilin binding polyketides that are structurally distinct from the cyclosporines and are produced by a microorganism amenable to biosynthetic engineering for lead optimization and large-scale production by fermentation. Preclinical characterization of the potential utility of this class of compounds for the treatment of HCV revealed that the natural sanglifehrins A to D are all more potent than CsA at disrupting formation of the NS5A-CypA, -CypB, and -CypD complexes and at inhibition of CypA, CypB, and CypD isomerase activity. In particular, sanglifehrin B (SfB) was 30- to 50-fold more potent at inhibiting the isomerase activity of all Cyps tested than CsA and was also shown to be a more potent inhibitor of the 1b subgenomic replicon (50% effective concentrations [EC 50 s] of 0.070 μM and 0.16 μM in Huh 5-2 and Huh 9-13 cells, respectively). Physicochemical and mouse pharmacokinetic analyses revealed low oral bioavailability ( F < 4%) and low solubility (<25 μM), although the half-lives ( t 1/2 ) of SfA and SfB in mouse blood after intravenous (i.v.) dosing were long ( t 1/2 > 5 h). These data demonstrate that naturally occurring sanglifehrins are suitable lead compounds for the development of novel analogues that are less immunosuppressive and that have improved metabolism and pharmacokinetic properties.Keywords:
Cypa
Cis-trans-Isomerases
Cyclophilin
Cyclophilins (Cyps) constitute one of the three families of peptidyl prolyl isomerase enzymes. CypA is the prototypical member of the Cyp family and is the predominant Cyp expressed in human cells. Recent studies indicate that CypA has an essential role in supporting HCV-specific RNA replication and protein expression. CypA interacts with several virally expressed proteins, including the non-structural (NS) proteins NS2, NS5A and NS5B, and may regulate diverse activities ranging from polypeptide processing to viral assembly. The introduction of non-immunosuppressive Cyp inhibitors into clinical trials confirms that Cyp inhibition is a valid strategy for developing novel therapeutics for the treatment of chronic HCV infection. This review describes the cyclophilin protein family and the potential roles played by cyclophilins in supporting HCV RNA replication and protein expression, as well as the initial clinical results obtained with a novel series of non-immunosuppressive cyclophilin inhibitors that established the clinical proof of concept for this emerging class of therapeutic agents.
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Peptidylprolyl isomerases (PPIase) cyclophilin A (CypA, encoded by PPIA) is a typical member of the Cyclophilin family and is involved in protein folding/translocation, signal transduction, inflammation, immune system regulation, apoptosis and virus replication. In the present study, we investigated the PPIase activity and genetic variation of vertebrate CypA. According to the GenBank reference sequences, vertebrate PPIA genes were cloned, among which the bat (Myotis davidi) and duck (Anas platyrhynchos) PPIA genes were reported for the first time. Then PPIA genes were sub-cloned into the expression vector pGEX-6p-1 and expressed in Escherichia coli. Recombinant CypA proteins were purified by using sepharose 4B affinity chromatography and the GST tag was cleaved, followed by gel filtration. The PPIase activity assay indicated that there was no significant difference in the catalytic activity of prolyl peptide bond isomerization among 12 different vertebrate CypA proteins. In addition, the genetic variation and molecular evolution analysis showed that these vertebrate CypA proteins had the same CsA binding site and the PPIase active sites. Furthermore, the predicted structure and gene localization were remarkable conserved. Our data suggested that the important residues of CypA were highly conserved, which is crucial for its PPIase activity and cellular functions.
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Cyclophilin A(CypA) is a member of cyclophilins,a family of the highly homologous peptidyl prolyl cis-trans isomerases(PPIases),which can bind to cyclosporin A(CsA).CypA plays critical roles in various biological processes,including protein folding,assembly,transportation,regulation of neuron growth and HIV replication.In the article,the whole development of natural product leads,peptide analogue inhibitors and organic synthesized compounds of CypA inhibitors was summarized and the research progress of CypA was reviewed.
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Cyclophilin is a cellular receptor for the immunosuppressive drug cyclosporin A (CsA). Cyclophilin C (CyPC) is highly expressed in murine kidney, making it a potential mediator of the nephrotoxic effects of CsA. The structure of murine CyPC complexed with CsA has been solved and refined to an R factor of 0.197 at a 1.64-A resolution. Superposition of the CyPC-CsA structure with the unligated cyclophilin A (CyPA) revealed significant migration of three loops: Gln-179 to Thr-189, Asp-47 to Lys-49, and Met-170 to Ile-176. The proximity of the loop Gln-179 to Thr-189 to the CsA binding site may account for the unique binding of a 77-kDa glycoprotein, CyPC binding protein (CyCAP), to CyPC. The binding of CsA to CyPC is similar to that of CsA to human T-cell cyclophilin A (CyPA). However, the conformation of CsA when bound to CyPC is significantly different from that when bound to CyPA. These differences may reflect conformational variation of CsA when bound to different proteins. Alternatively, the previous CyPA-CsA structure at low resolution may not provide sufficient details for a comparison with the CyPC-CsA structure.
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Cyclophilin A(CyPA),a 20 kD chaperone protein with the peptidylprolyl-cis-trans-isomerase(PPIase)-like activity,is a member of the immunophilin family.CyPA plays an important role in protein folding,signal transduction,oxidative stress,and inflammatory response.In recent years,the research about CyPA mainly focuses on its role in various viral diseases,such as viral hepatitis(HBV/HCV),acquired immunodeficiency syndrome(AIDS) and influenza A H1N1 bird flu(influenza virus A).It is necessary to do further studies to elucidate the role of CypA in viral diseases and the underlying molecular mechanisms.
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Peptidylprolyl isomerases (PPIases) catalyze cis/trans isomerization of prolines. The PPIase CypA colocalizes with the Parkinson's disease (PD)-associated protein α-synuclein in cells and interacts with α-synuclein oligomers. Herein, we describe atomic insights into the molecular details of the α-synuclein/CypA interaction. NMR spectroscopy shows that CypA catalyzes isomerization of proline 128 in the C-terminal domain of α-synuclein. Strikingly, we reveal a second CypA-binding site formed by the hydrophobic sequence
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