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Barelli H, Camonis J, de Gunzburg J, Goud B, Moreau-Gachelin F, Wittinghofer A, Zahraoui A. Pierre Chardin, un pionnier de la découverte des gènes et protéines de la superfamille Ras. Med Sci (Paris) 2020; 36:394-398. [DOI: 10.1051/medsci/2020058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Klink BU, Gatsogiannis C, Hofnagel O, Wittinghofer A, Raunser S. Structure of the human BBSome core complex. eLife 2020; 9:53910. [PMID: 31951201 PMCID: PMC7018512 DOI: 10.7554/elife.53910] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 01/15/2020] [Indexed: 01/09/2023] Open
Abstract
The BBSome is a heterooctameric protein complex that plays a central role in primary cilia homeostasis. Its malfunction causes the severe ciliopathy Bardet-Biedl syndrome (BBS). The complex acts as a cargo adapter that recognizes signaling proteins such as GPCRs and links them to the intraflagellar transport machinery. The underlying mechanism is poorly understood. Here we present a high-resolution cryo-EM structure of a human heterohexameric core subcomplex of the BBSome. The structure reveals the architecture of the complex in atomic detail. It explains how the subunits interact with each other and how disease-causing mutations hamper this interaction. The complex adopts a conformation that is open for binding to membrane-associated GTPase Arl6 and a large positively charged patch likely strengthens the interaction with the membrane. A prominent negatively charged cleft at the center of the complex is likely involved in binding of positively charged signaling sequences of cargo proteins.
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Wauters L, Terheyden S, Gilsbach BK, Leemans M, Athanasopoulos PS, Guaitoli G, Wittinghofer A, Gloeckner CJ, Versées W, Kortholt A. Biochemical and kinetic properties of the complex Roco G-protein cycle. Biol Chem 2019; 399:1447-1456. [PMID: 30067506 DOI: 10.1515/hsz-2018-0227] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 07/23/2018] [Indexed: 12/12/2022]
Abstract
Roco proteins have come into focus after mutations in the gene coding for the human Roco protein Leucine-rich repeat kinase 2 (LRRK2) were discovered to be one of the most common genetic causes of late onset Parkinson's disease. Roco proteins are characterized by a Roc domain responsible for GTP binding and hydrolysis, followed by a COR dimerization device. The regulation and function of this RocCOR domain tandem is still not completely understood. To fully biochemically characterize Roco proteins, we performed a systematic survey of the kinetic properties of several Roco protein family members, including LRRK2. Together, our results show that Roco proteins have a unique G-protein cycle. Our results confirm that Roco proteins have a low nucleotide affinity in the micromolar range and thus do not strictly depend on G-nucleotide exchange factors. Measurement of multiple and single turnover reactions shows that neither Pi nor GDP release are rate-limiting, while this is the case for the GAP-mediated GTPase reaction of some small G-proteins like Ras and for most other high affinity Ras-like proteins, respectively. The KM values of the reactions are in the range of the physiological GTP concentration, suggesting that LRRK2 functioning might be regulated by the cellular GTP level.
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Kösling SK, Fansa EK, Maffini S, Wittinghofer A. Mechanism and dynamics of INPP5E transport into and inside the ciliary compartment. Biol Chem 2018; 399:277-292. [PMID: 29140789 DOI: 10.1515/hsz-2017-0226] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 11/03/2017] [Indexed: 11/15/2022]
Abstract
The inositol polyphosphate 5'-phosphatase E (INPP5E) localizes to cilia. We showed that the carrier protein phosphodiesterase 6 delta subunit (PDE6δ) mediates the sorting of farnesylated INPP5E into cilia due to high affinity binding and release by the ADP-ribosylation factor (Arf)-like protein Arl3·GTP. However, the dynamics of INPP5E transport into and inside the ciliary compartment are not fully understood. Here, we investigate the movement of INPP5E using live cell fluorescence microscopy and fluorescence recovery after photobleaching (FRAP) analysis. We show that PDE6δ and the dynein transport system are essential for ciliary sorting and entry of INPP5E. However, its innerciliary transport is regulated solely by the intraflagellar transport (IFT) system, independent from PDE6δ activity and INPP5E farnesylation. By contrast, movement of Arl3 into and within cilia occurs freely by diffusion and IFT-independently. The farnesylation defective INPP5E CaaX box mutant loses the exclusive ciliary localization. The accumulation of this mutant at centrioles after photobleaching suggests an affinity trap mechanism for ciliary entry, that in case of the wild type is overcome by the interaction with PDE6δ. Collectively, we postulate a three-step mechanism regulating ciliary localization of INPP5E, consisting of farnesylation- and PDE6δ-mediated targeting, INPP5E-PDE6δ complex diffusion into the cilium with transfer to the IFT system, and retention inside cilia.
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Lyraki R, Lokaj M, Soares DC, Little A, Vermeren M, Marsh JA, Wittinghofer A, Hurd T. Characterization of a novel RP2-OSTF1 interaction and its implication for actin remodelling. J Cell Sci 2018; 131:jcs.211748. [PMID: 29361551 DOI: 10.1242/jcs.211748] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 12/21/2017] [Indexed: 11/20/2022] Open
Abstract
Retinitis pigmentosa 2 (RP2) is the causative gene for a form of X-linked retinal degeneration. RP2 was previously shown to have GTPase-activating protein (GAP) activity towards the small GTPase ARL3 via its N-terminus, but the function of the C-terminus remains elusive. Here, we report a novel interaction between RP2 and osteoclast-stimulating factor 1 (OSTF1), an intracellular protein that indirectly enhances osteoclast formation and activity and is a negative regulator of cell motility. Moreover, this interaction is abolished by a human pathogenic mutation in RP2. We utilized a structure-based approach to pinpoint the binding interface to a strictly conserved cluster of residues on the surface of RP2 that spans both the C- and N-terminal domains of the protein, and which is structurally distinct from the ARL3-binding site. In addition, we show that RP2 is a positive regulator of cell motility in vitro, recruiting OSTF1 to the cell membrane and preventing its interaction with the migration regulator Myo1E.
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Cuellar J, Valpuesta JM, Wittinghofer A, Sot B. Domain topology of human Rasal. Biol Chem 2017; 399:63-72. [PMID: 28885980 DOI: 10.1515/hsz-2017-0159] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 08/31/2017] [Indexed: 01/15/2023]
Abstract
Rasal is a modular multi-domain protein of the GTPase-activating protein 1 (GAP1) family; its four known members, GAP1m, Rasal, GAP1IP4BP and Capri, have a Ras GTPase-activating domain (RasGAP). This domain supports the intrinsically slow GTPase activity of Ras by actively participating in the catalytic reaction. In the case of Rasal, GAP1IP4BP and Capri, their remaining domains are responsible for converting the RasGAP domains into dual Ras- and Rap-GAPs, via an incompletely understood mechanism. Although Rap proteins are small GTPase homologues of Ras, their catalytic residues are distinct, which reinforces the importance of determining the structure of full-length GAP1 family proteins. To date, these proteins have not been crystallized, and their size is not adequate for nuclear magnetic resonance (NMR) or for high-resolution cryo-electron microscopy (cryoEM). Here we present the low resolution structure of full-length Rasal, obtained by negative staining electron microscopy, which allows us to propose a model of its domain topology. These results help to understand the role of the different domains in controlling the dual GAP activity of GAP1 family proteins.
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Klink BU, Zent E, Juneja P, Kuhlee A, Raunser S, Wittinghofer A. A recombinant BBSome core complex and how it interacts with ciliary cargo. eLife 2017; 6. [PMID: 29168691 PMCID: PMC5700813 DOI: 10.7554/elife.27434] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 11/03/2017] [Indexed: 01/07/2023] Open
Abstract
Cilia are small, antenna-like structures on the surface of eukaryotic cells that harbor a unique set of sensory proteins, including GPCRs and other membrane proteins. The transport of these proteins involves the BBSome, an eight-membered protein complex that is recruited to ciliary membranes by the G-protein Arl6. BBSome malfunction leads to Bardet-Biedl syndrome, a ciliopathy with severe consequences. Short ciliary targeting sequences (CTS) have been identified that trigger the transport of ciliary proteins. However, mechanistic studies that relate ciliary targeting to BBSome binding are missing. Here we used heterologously expressed BBSome subcomplexes to analyze the complex architecture and to investigate the binding of GPCRs and other receptors to the BBSome. A stable heterohexameric complex was identified that binds to GPCRs with interactions that only partially overlap with previously described CTS, indicating a more complex recognition than anticipated. Arl6•GTP does not affect these interactions, suggesting no direct involvement in cargo loading/unloading.
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Martín-Gago P, Fansa EK, Wittinghofer A, Waldmann H. Structure-based development of PDEδ inhibitors. Biol Chem 2017; 398:535-545. [PMID: 27935847 DOI: 10.1515/hsz-2016-0272] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 11/06/2016] [Indexed: 11/15/2022]
Abstract
The prenyl binding protein PDEδ enhances the diffusion of farnesylated Ras proteins in the cytosol, ultimately affecting their correct localization and signaling. This has turned PDEδ into a promising target to prevent oncogenic KRas signaling. In this review we summarize and describe the structure-guided-development of the three different PDEδ inhibitor chemotypes that have been documented so far. We also compare both their potency for binding to the PDEδ pocket and their in vivo efficiency in suppressing oncogenic KRas signaling, as a result of the inhibition of the PDEδ/KRas interaction.
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Mejuch T, Garivet G, Hofer W, Kaiser N, Fansa EK, Ehrt C, Koch O, Baumann M, Ziegler S, Wittinghofer A, Waldmann H. Small-Molecule Inhibition of the UNC119-Cargo Interaction. Angew Chem Int Ed Engl 2017; 56:6181-6186. [DOI: 10.1002/anie.201701905] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 03/30/2017] [Indexed: 01/10/2023]
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Mejuch T, Garivet G, Hofer W, Kaiser N, Fansa EK, Ehrt C, Koch O, Baumann M, Ziegler S, Wittinghofer A, Waldmann H. Small-Molecule Inhibition of the UNC119-Cargo Interaction. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201701905] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Murarka S, Martín-Gago P, Schultz-Fademrecht C, Al Saabi A, Baumann M, Fansa EK, Ismail S, Nussbaumer P, Wittinghofer A, Waldmann H. Development of Pyridazinone Chemotypes Targeting the PDEδ Prenyl Binding Site. Chemistry 2017; 23:6083-6093. [PMID: 27809361 DOI: 10.1002/chem.201603222] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Indexed: 12/18/2022]
Abstract
The K-Ras GTPase is a major target in anticancer drug discovery. However, direct interference with signaling by K-Ras has not led to clinically useful drugs yet. Correct localization and signaling by farnesylated K-Ras is regulated by the prenyl binding protein PDEδ. Interfering with binding of PDEδ to K-Ras by means of small molecules provides a novel opportunity to suppress oncogenic signaling. Here we describe the identification and structure-guided development of novel K-Ras-PDEδ inhibitor chemotypes based on pyrrolopyridazinones and pyrazolopyridazinones that bind to the farnesyl binding pocket of PDEδ with low nanomolar affinity. We delineate the structure-property relationship and in vivo pharmacokinetic (PK) and toxicokinetic (Tox) studies for pyrazolopyridazinone-based K-Ras-PDEδ inhibitors. These findings may inspire novel drug discovery efforts aimed at the development of drugs targeting oncogenic Ras.
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Martín-Gago P, Fansa EK, Winzker M, Murarka S, Janning P, Schultz-Fademrecht C, Baumann M, Wittinghofer A, Waldmann H. Covalent Protein Labeling at Glutamic Acids. Cell Chem Biol 2017; 24:589-597.e5. [DOI: 10.1016/j.chembiol.2017.03.015] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/07/2017] [Accepted: 03/24/2017] [Indexed: 12/26/2022]
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Blackburn GM, Cherfils J, Moss GP, Richards NGJ, Waltho JP, Williams NH, Wittinghofer A. How to name atoms in phosphates, polyphosphates, their derivatives and mimics, and transition state analogues for enzyme-catalysed phosphoryl transfer reactions (IUPAC Recommendations 2016). PURE APPL CHEM 2017. [DOI: 10.1515/pac-2016-0202] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractProcedures are proposed for the naming of individual atoms, P, O, F, N, and S in phosphate esters, amidates, thiophosphates, polyphosphates, their mimics, and analogues of transition states for enzyme-catalyzed phosphoryl transfer reactions. Their purpose is to enable scientists in very different fields, e.g. biochemistry, biophysics, chemistry, computational chemistry, crystallography, and molecular biology, to share standard protocols for the labelling of individual atoms in complex molecules. This will facilitate clear and unambiguous descriptions of structural results, as well as scientific intercommunication concerning them. At the present time, perusal of the Protein Data Bank (PDB) and other sources shows that there is a limited degree of commonality in nomenclature, but a large measure of irregularity in more complex structures. The recommendations described here adhere to established practice as closely as possible, in particular to IUPAC and IUBMB recommendations and to “best practice” in the PDB, especially to its atom labelling of amino acids, and particularly to Cahn-Ingold-Prelog rules for stereochemical nomenclature. They are designed to work in complex enzyme sites for binding phosphates but also to have utility for non-enzymatic systems. Above all, the recommendations are designed to be easy to comprehend and user-friendly.
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Martín-Gago P, Fansa EK, Klein CH, Murarka S, Janning P, Schürmann M, Metz M, Ismail S, Schultz-Fademrecht C, Baumann M, Bastiaens PIH, Wittinghofer A, Waldmann H. A PDE6δ-KRas Inhibitor Chemotype with up to Seven H-Bonds and Picomolar Affinity that Prevents Efficient Inhibitor Release by Arl2. Angew Chem Int Ed Engl 2017; 56:2423-2428. [PMID: 28106325 DOI: 10.1002/anie.201610957] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Indexed: 12/11/2022]
Abstract
Small-molecule inhibition of the interaction between the KRas oncoprotein and the chaperone PDE6δ impairs KRas spatial organization and signaling in cells. However, despite potent binding in vitro (KD <10 nm), interference with Ras signaling and growth inhibition require 5-20 μm compound concentrations. We demonstrate that these findings can be explained by fast release of high-affinity inhibitors from PDE6δ by the release factor Arl2. This limitation is overcome by novel highly selective inhibitors that bind to PDE6δ with up to 7 hydrogen bonds, resulting in picomolar affinity. Their release by Arl2 is greatly decreased, and representative compounds selectively inhibit growth of KRas mutated and -dependent cells with the highest activity recorded yet. Our findings indicate that very potent inhibitors of the KRas-PDE6δ interaction may impair the growth of tumors driven by oncogenic KRas.
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Martín-Gago P, Fansa EK, Klein CH, Murarka S, Janning P, Schürmann M, Metz M, Ismail S, Schultz-Fademrecht C, Baumann M, Bastiaens PIH, Wittinghofer A, Waldmann H. A PDE6δ-KRas Inhibitor Chemotype with up to Seven H-Bonds and Picomolar Affinity that Prevents Efficient Inhibitor Release by Arl2. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201610957] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Abstract
Arl2 and Arl3 are Arf-like small GTP-binding proteins of the Arf subfamily of the Ras superfamily. Despite their structural similarity and sharing of many interacting partners, Arl2 and Arl3 have different biochemical properties and biological functions. Growing evidence suggest that Arl2 and Arl3 play a fundamental role as regulators of trafficking of lipid modified proteins between different compartments. Here we highlight the similarities and differences between these 2 homologous proteins and discuss the sorting mechanism of lipidated cargo into the ciliary compartment through the carriers PDE6δ and Unc119 and the release factors Arl2 and Arl3.
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Jaiswal M, Fansa EK, Kösling SK, Mejuch T, Waldmann H, Wittinghofer A. Novel Biochemical and Structural Insights into the Interaction of Myristoylated Cargo with Unc119 Protein and Their Release by Arl2/3. J Biol Chem 2016; 291:20766-78. [PMID: 27481943 PMCID: PMC5034065 DOI: 10.1074/jbc.m116.741827] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 07/29/2016] [Indexed: 11/06/2022] Open
Abstract
Primary cilia are highly specialized small antenna-like cellular protrusions that extend from the cell surface of many eukaryotic cell types. The protein content inside cilia and cytoplasm is very different, but details of the sorting process are not understood for most ciliary proteins. Recently, we have shown that prenylated proteins are sorted according to their affinity to the carrier protein PDE6δ and the ability of Arl3 but not Arl2 to release high affinity cargo inside the cilia (Fansa, E. K., Kösling, S. K., Zent, E., Wittinghofer, A., and Ismail, S. (2016) Nat. Commun. 7, 11366). Here we address the question whether a similar principle governs the transport of myristoylated cargo by the carrier proteins Unc119a and Unc119b. We thus analyzed the binding strength of N-terminal myristoylated cargo peptides (GNAT1, NPHP3, Cystin1, RP2, and Src) to Unc119a and Unc119b proteins. The affinity between myristoylated cargo and carrier protein, Unc119, varies between subnanomolar and micromolar. Peptides derived from ciliary localizing proteins (GNAT1, NPHP3, and Cystin1) bind with high affinity to Unc119 proteins, whereas a peptide derived from a non-ciliary localizing protein (Src) has low affinity. The peptide with intermediate affinity (RP2) is localized at the ciliary transition zone as a gate keeper. We show that the low affinity peptides are released by both Arl2·GppNHp and Arl3·GppNHp, whereas the high affinity peptides are exclusively released by only Arl3·GppNHp. Determination of the x-ray structure of myristoylated NPHP3 peptide in complex with Unc119a reveals the molecular details of high affinity binding and suggests the importance of the residues at the +2 and +3 positions relative to the myristoylated glycine for high and low affinities. The mutational analysis of swapping the residues at the +2 and +3 positions between high and low affinity peptides results in reversing their affinities for Unc119a and leads to a partial mislocalization of a low affinity mutant of NPHP3.
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Wittinghofer A, Martin JB, Blacklow S. Proteins special issue of biopolymers. Biopolymers 2016; 99:807-8. [PMID: 23893350 DOI: 10.1002/bip.22353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Papke B, Murarka S, Vogel HA, Martín-Gago P, Kovacevic M, Truxius DC, Fansa EK, Ismail S, Zimmermann G, Heinelt K, Schultz-Fademrecht C, Al Saabi A, Baumann M, Nussbaumer P, Wittinghofer A, Waldmann H, Bastiaens PI. Identification of pyrazolopyridazinones as PDEδ inhibitors. Nat Commun 2016; 7:11360. [PMID: 27094677 PMCID: PMC4843002 DOI: 10.1038/ncomms11360] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 03/17/2016] [Indexed: 12/21/2022] Open
Abstract
The prenyl-binding protein PDEδ is crucial for the plasma membrane localization of prenylated Ras. Recently, we have reported that the small-molecule Deltarasin binds to the prenyl-binding pocket of PDEδ, and impairs Ras enrichment at the plasma membrane, thereby affecting the proliferation of KRas-dependent human pancreatic ductal adenocarcinoma cell lines. Here, using structure-based compound design, we have now identified pyrazolopyridazinones as a novel, unrelated chemotype that binds to the prenyl-binding pocket of PDEδ with high affinity, thereby displacing prenylated Ras proteins in cells. Our results show that the new PDEδ inhibitor, named Deltazinone 1, is highly selective, exhibits less unspecific cytotoxicity than the previously reported Deltarasin and demonstrates a high correlation with the phenotypic effect of PDEδ knockdown in a set of human pancreatic cancer cell lines.
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Blaževitš O, Mideksa YG, Šolman M, Ligabue A, Ariotti N, Nakhaeizadeh H, Fansa EK, Papageorgiou AC, Wittinghofer A, Ahmadian MR, Abankwa D. Galectin-1 dimers can scaffold Raf-effectors to increase H-ras nanoclustering. Sci Rep 2016; 6:24165. [PMID: 27087647 PMCID: PMC4834570 DOI: 10.1038/srep24165] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 03/22/2016] [Indexed: 12/12/2022] Open
Abstract
Galectin-1 (Gal-1) dimers crosslink carbohydrates on cell surface receptors. Carbohydrate-derived inhibitors have been developed for cancer treatment. Intracellularly, Gal-1 was suggested to interact with the farnesylated C-terminus of Ras thus specifically stabilizing GTP-H-ras nanoscale signalling hubs in the membrane, termed nanoclusters. The latter activity may present an alternative mechanism for how overexpressed Gal-1 stimulates tumourigenesis. Here we revise the current model for the interaction of Gal-1 with H-ras. We show that it indirectly forms a complex with GTP-H-ras via a high-affinity interaction with the Ras binding domain (RBD) of Ras effectors. A computationally generated model of the Gal-1/C-Raf-RBD complex is validated by mutational analysis. Both cellular FRET as well as proximity ligation assay experiments confirm interaction of Gal-1 with Raf proteins in mammalian cells. Consistently, interference with H-rasG12V-effector interactions basically abolishes H-ras nanoclustering. In addition, an intact dimer interface of Gal-1 is required for it to positively regulate H-rasG12V nanoclustering, but negatively K-rasG12V nanoclustering. Our findings suggest stacked dimers of H-ras, Raf and Gal-1 as building blocks of GTP-H-ras-nanocluster at high Gal-1 levels. Based on our results the Gal-1/effector interface represents a potential drug target site in diseases with aberrant Ras signalling.
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Fansa EK, Kösling SK, Zent E, Wittinghofer A, Ismail S. PDE6δ-mediated sorting of INPP5E into the cilium is determined by cargo-carrier affinity. Nat Commun 2016; 7:11366. [PMID: 27063844 PMCID: PMC5512577 DOI: 10.1038/ncomms11366] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 03/18/2016] [Indexed: 01/06/2023] Open
Abstract
The phosphodiesterase 6 delta subunit (PDE6δ) shuttles several farnesylated cargos between membranes. The cargo sorting mechanism between cilia and other compartments is not understood. Here we show using the inositol polyphosphate 5'-phosphatase E (INPP5E) and the GTP-binding protein (Rheb) that cargo sorting depends on the affinity towards PDE6δ and the specificity of cargo release. High-affinity cargo is exclusively released by the ciliary transport regulator Arl3, while low-affinity cargo is released by Arl3 and its non-ciliary homologue Arl2. Structures of PDE6δ/cargo complexes reveal the molecular basis of the sorting signal which depends on the residues at the -1 and -3 positions relative to farnesylated cysteine. Structure-guided mutation allows the generation of a low-affinity INPP5E mutant which loses exclusive ciliary localization. We postulate that the affinity to PDE6δ and the release by Arl2/3 in addition to a retention signal are the determinants for cargo sorting and enrichment at its destination.
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Abstract
Two recent studies evaluated a small molecule that specifically binds to and inactivates the KRAS G12C mutant. The new findings argue that the perception that mutant KRAS is persistently frozen in its active GTP-bound form may not be accurate.
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Ismail-Ali A, Fansa EK, Pryk N, Yahiaoui S, Kushnir S, Pflieger M, Wittinghofer A, Schulz F. Biosynthesis-driven structure–activity relationship study of premonensin-derivatives. Org Biomol Chem 2016; 14:7671-5. [DOI: 10.1039/c6ob01201a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The controlled derivatization of natural products is of great importance for their use in drug discovery.
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Abstract
This study shows that the prenylated C‐terminus of RPGR can bind to PDE6δ with high affinity, suggesting two distinct binding sites of the RPGR/PDE6δ complex. The serine residue at the −3 position relative to the prenylated cysteine seems to play a key role in defining the selectivity of PDE6δ towards ciliary prenylated cargo.
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