E Anouk Stigter

University of Bayreuth, Bayreuth, Bavaria, Germany

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Publications (4)28.82 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Members of the Ras superfamily of small GTPases are frequently mutated in cancer. Therefore, inhibitors have been developed to address the acitivity of these GTPases by inhibiting their prenylating enzymes FTase, GGTase I, and RabGGTase. In contrast to FTase and GGTase I, only a handful of RabGGTase inhibitors have been developed. The most active RabGGTase inhibitor known until recently was an FTase inhibitor which hit RabGGTase as an off-target. We recently reported our efforts to tune the selectivity of these inhibitors toward RabGGTase. Here we describe an extended set of selective inhibitors. The requirements for selective RabGGTase inhibitors are described in detail, guided by multiple crystal structures. In order to relate in vitro and cellular activity, a high-throughput assay system to detect the attachment of [(3)H]geranylgeranyl groups to Rab was used. Selective RabGGTase inhibition allows the establishment of novel drug discovery programs aimed at the development of anticancer therapeutics.
    No preview · Article · Sep 2012 · Journal of Medicinal Chemistry
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    ABSTRACT: Post-translational attachment of geranylgeranyl isoprenoids to Rab GTPases, the key organizers of intracellular vesicular transport, is essential for their function. Rab geranylgeranyl transferase (RabGGTase) is responsible for prenylation of Rab proteins. Recently, RabGGTase inhibitors have been proposed to be potential therapeutics for treatment of cancer and osteoporosis. However, the development of RabGGTase selective inhibitors is complicated by its structural and functional similarity to other protein prenyltransferases. Herein we report identification of the natural product psoromic acid (PA) that potently and selectively inhibits RabGGTase with an IC(50) of 1.3 μM. Structure-activity relationship analysis suggested a minimal structure involving the depsidone core with a 3-hydroxyl and 4-aldehyde motif for binding to RabGGTase. Analysis of the crystal structure of the RabGGTase:PA complex revealed that PA forms largely hydrophobic interactions with the isoprenoid binding site of RabGGTase and that it attaches covalently to the N-terminus of the α subunit. We found that in contrast to other protein prenyltransferases, RabGGTase is autoinhibited through N-terminal (α)His2 coordination with the catalytic zinc ion. Mutation of (α)His dramatically enhances the reaction rate, indicating that the activity of RabGGTase is likely regulated in vivo. The covalent binding of PA to the N-terminus of the RabGGTase α subunit seems to potentiate its interaction with the active site and explains the selectivity of PA for RabGGTase. Therefore, psoromic acid provides a new starting point for the development of selective RabGGTase inhibitors.
    No preview · Article · Apr 2012 · Journal of the American Chemical Society
  • E. Anouk Stigter · Gemma Triola · Roger S. Goody · Herbert Waldmann
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    ABSTRACT: Posttranslational lipidation is essential for a correct membrane association and function of numerous proteins such as several members of the Ras superfamily of small guanosine triphosphatases. The most common lipid modifications are N-myristoylation or S-palmitoylation and the isoprenylation of cysteines. Two different isoprenoid groups can be added to proteins. Farnesyl transferases (FTase) introduce the 15-carbon farnesyl while the 20-carbon geranylgeranyl group can be added by geranylgeranyl transferase I (GGTase I) or Rab geranylgeranyl transferase (RabGGTase/GGTase II), which acts specifically on Rab proteins, important regulators of vesicular transport. The subfamily of Ras GTPases controls numerous signaling cascades, andmutations in these proteins have been associatedwith cancer. Since membrane association is crucial for their activity, inhibition of FTase and GGTase has been explored as anticancer strategy, although with poor success. However, a new therapeutic strategy was opened after observing that unselective FTase and RabGGTase inhibitors had a remarkably inhibitory effect on tumor cell lines with no mutations in Ras. In recent years, much work has been dedicated to the development of selectiveRabGGTase inhibitors. Even though this has been challenging due to the close similarity of the active sites of the different prenyl transferases, important advances have already been achieved in this direction. This review will highlight the most prominent RabGGTase inhibitor classes, from the initial phosphonocarboxylates or GGPP mimics, to peptide-based and small molecules inhibitors. After a description of each compound class, we will provide an overview of their selectivity profile and their biological evaluation will be discussed in detail.
    No preview · Chapter · Dec 2011
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    ABSTRACT: Designing for selectivity: A combination of protein crystal-structure analysis, virtual screening, and synthetic chemistry has been used to develop noncytotoxic inhibitors of RabGGTase (IC50: 42nM for the example shown; red O, blue N, yellow S) that are selective over FTase and GGTaseI. Furthermore, the inhibitors display cellular activity and inhibit cancer cell proliferation.
    No preview · Article · May 2011 · Angewandte Chemie International Edition

Publication Stats

46 Citations
28.82 Total Impact Points


  • 2012
    • University of Bayreuth
      • Chair of Biochemistry
      Bayreuth, Bavaria, Germany
  • 2011-2012
    • Max Planck Institute of Molecular Physiology
      • Department of Chemical Biology
      Dortmund, North Rhine-Westphalia, Germany