101
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Minutolo F, Bertini S, Betti L, Danesi R, Gervasi G, Giannaccini G, Martinelli A, Papini AM, Peroni E, Placanica G, Rapposelli S, Tuccinardi T, Macchia M. Synthesis of stable analogues of geranylgeranyl diphosphate possessing a (Z,E,E)-geranylgeranyl side chain, docking analysis, and biological assays for prenyl protein transferase inhibition. ChemMedChem 2006; 1:218-24. [PMID: 16892354 DOI: 10.1002/cmdc.200500010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Herein, we report the synthesis of novel stable analogues of geranylgeranyl diphosphate (GGPP), in which the "natural" all-trans geranylgeranyl portion has been replaced by a (Z,E,E)-geranylgeranyl chain. The change in configuration and consequent change in the relative position of the polar portion with the lipophilic side chain did not improve the properties of the E,E,E analogues in their inhibition of geranylgeranyl protein transferase I (GGTase I). However, a significant level of GGTase I inhibition and selectivity for GGTase I over farnesyl transferase (FTase) was maintained the unsubstituted phosphonoacetamidoxy derivative 4 a. This has shed light on the relative importance of the configuration at the C2=C3 double bond among GGPP derivatives. Moreover, the biological activities of all the compounds reported herein, in particular the preferential FTase inhibitory activity shown by compound 6, were in good agreement with the results of docking analysis.
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Affiliation(s)
- Filippo Minutolo
- Dipartimento di Scienze Farmaceutiche, Università di Pisa, Via Bonanno 6, 56126 Pisa, Italy
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102
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Iwata K, Li J, Follet H, Phipps RJ, Burr DB. Bisphosphonates suppress periosteal osteoblast activity independently of resorption in rat femur and tibia. Bone 2006; 39:1053-1058. [PMID: 16807159 DOI: 10.1016/j.bone.2006.05.006] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 04/14/2006] [Accepted: 05/03/2006] [Indexed: 01/06/2023]
Abstract
Recent studies demonstrate that bisphosphonates suppress bone resorption by leading to apoptosis of the osteoclast and inhibiting the differentiation to mature osteoclasts. The influence of bisphosphonates on bone formation is unknown, although it has been hypothesized that bisphosphonates inhibit osteoblast apoptosis and stimulate osteoblast proliferation and differentiation in vitro, leading to increased bone formation. The purpose of this study was to investigate the effect of bisphosphonates on bone formation. We administered risedronate at 0.05, 0.5 or 5.0 microg/kg/day or alendronate at 0.1, 1.0 or 10 microg/kg/day subcutaneously for 17 days to 6-month-old female Sprague-Dawley rats. Control rats were given a daily subcutaneous injection of saline. Following sacrifice, the femoral and tibial mid-diaphyses were harvested and mineralizing surface (MS/BS), mineral apposition rate (MAR) and bone formation rate (BFR/BS) were measured on periosteal and endocortical surfaces. In the femur, periosteal MAR was significantly lower in all treatment groups (22-29% for risedronate, 26-36% for alendronate) than in control. In the tibia, periosteal MAR and BFR of all treatment groups were significantly lower (41-50% for risedronate, 43-52% for alendronate) than in the control group. Because the periosteal surfaces of these bones are only undergoing bone formation in modeling mode, our results show that bisphosphonates suppress bone formation independently of bone resorption. Because this effect is seen on periosteal MAR rather than on periosteal MS/BS, we hypothesize that bisphosphonates affect the activity of individual osteoblasts at the cell level. This may help to explain the reason that the anabolic effects of teriparatide are blunted when administered concurrently with or following a course of bisphosphonates in humans.
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Affiliation(s)
- Ken Iwata
- Indiana Uníversity School of Medicine, IN 46202, USA
| | - Jiliang Li
- Indiana Uníversity School of Medicine, IN 46202, USA
| | - Helene Follet
- Indiana Uníversity School of Medicine, IN 46202, USA
| | | | - David B Burr
- Indiana Uníversity School of Medicine, IN 46202, USA.
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103
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Conesa Mateos A, Rotés Sala D, Almirall Bernabé M, Carbonell Abelló J. Eficacia del ácido zoledrónico en la enfermedad ósea de Paget: tres años de experiencia. Med Clin (Barc) 2006; 127:635-6. [PMID: 17145033 DOI: 10.1157/13094423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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104
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Kavanagh KL, Dunford JE, Bunkoczi G, Russell RGG, Oppermann U. The crystal structure of human geranylgeranyl pyrophosphate synthase reveals a novel hexameric arrangement and inhibitory product binding. J Biol Chem 2006; 281:22004-22012. [PMID: 16698791 DOI: 10.1074/jbc.m602603200] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Modification of GTPases with isoprenoid molecules derived from geranylgeranyl pyrophosphate or farnesyl pyrophosphate is an essential requisite for cellular signaling pathways. The synthesis of these isoprenoids proceeds in mammals through the mevalonate pathway, and the final steps in the synthesis are catalyzed by the related enzymes farnesyl pyrophosphate synthase and geranylgeranyl pyrophosphate synthase. Both enzymes play crucial roles in cell survival, and inhibition of farnesyl pyrophosphate synthase by nitrogen-containing bisphosphonates is an established concept in the treatment of bone disorders such as osteoporosis or certain forms of cancer in bone. Here we report the crystal structure of human geranylgeranyl pyrophosphate synthase, the first mammalian ortholog to have its x-ray structure determined. It reveals that three dimers join together to form a propeller-bladed hexameric molecule with a mass of approximately 200 kDa. Structure-based sequence alignments predict this quaternary structure to be restricted to mammalian and insect orthologs, whereas fungal, bacterial, archaeal, and plant forms exhibit the dimeric organization also observed in farnesyl pyrophosphate synthase. Geranylgeranyl pyrophosphate derived from heterologous bacterial expression is tightly bound in a cavity distinct from the chain elongation site described for farnesyl pyrophosphate synthase. The structure most likely represents an inhibitory complex, which is further corroborated by steady-state kinetics, suggesting a possible feedback mechanism for regulating enzyme activity. Structural comparisons between members of this enzyme class give deeper insights into conserved features important for catalysis.
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Affiliation(s)
- Kathryn L Kavanagh
- Structural Genomics Consortium, Botnar Research Centre, University of Oxford, Oxford OX3 7LD, United Kingdom.
| | - James E Dunford
- Structural Genomics Consortium, Botnar Research Centre, University of Oxford, Oxford OX3 7LD, United Kingdom; Institute of Musculoskeletal Sciences, Botnar Research Centre, Nuffield Department of Orthopaedic Surgery, University of Oxford, Oxford OX3 7LD, United Kingdom
| | - Gabor Bunkoczi
- Structural Genomics Consortium, Botnar Research Centre, University of Oxford, Oxford OX3 7LD, United Kingdom
| | - R Graham G Russell
- Institute of Musculoskeletal Sciences, Botnar Research Centre, Nuffield Department of Orthopaedic Surgery, University of Oxford, Oxford OX3 7LD, United Kingdom
| | - Udo Oppermann
- Structural Genomics Consortium, Botnar Research Centre, University of Oxford, Oxford OX3 7LD, United Kingdom.
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105
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Dursina B, Reents R, Delon C, Wu Y, Kulharia M, Thutewohl M, Veligodsky A, Kalinin A, Evstifeev V, Ciobanu D, Szedlacsek SE, Waldmann H, Goody RS, Alexandrov K. Identification and specificity profiling of protein prenyltransferase inhibitors using new fluorescent phosphoisoprenoids. J Am Chem Soc 2006; 128:2822-35. [PMID: 16506760 DOI: 10.1021/ja052196e] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Posttranslational modification of proteins with farnesyl and geranylgeranyl isoprenoids is a widespread phenomenon in eukaryotic organisms. Isoprenylation is conferred by three protein prenyltransferases: farnesyl transferase (FTase), geranylgeranyl transferase type-I (GGTase-I), and Rab geranylgeranyltransferase (RabGGTase). Inhibitors of these enzymes have emerged as promising therapeutic compounds for treatment of cancer, viral and parasite originated diseases, as well as osteoporosis. However, no generic nonradioactive protein prenyltransferase assay has been reported to date, complicating identification of enzyme-specific inhibitors. We have addressed this issue by developing two fluorescent analogues of farnesyl and geranylgeranyl pyrophosphates {3,7-dimethyl-8-(7-nitro-benzo[1,2,5]oxadiazol-4-ylamino)-octa-2,6-diene-1}pyrophosphate (NBD-GPP) and {3,7,11-trimethyl-12-(7-nitro-benzo[1,2,5]oxadiazo-4-ylamino)-dodeca-2,6,10-trien-1} pyrophosphate (NBD-FPP), respectively. We demonstrate that these compounds can serve as efficient lipid donors for prenyltransferases. Using these fluorescent lipids, we have developed two simple (SDS-PAGE and bead-based) in vitro prenylation assays applicable to all prenyltransferases. Using the SDS-PAGE assay, we found that, in contrast to previous reports, the tyrosine phosphatase PRL-3 may possibly be a dual substrate for both FTase and GGTase-I. The on-bead prenylation assay was used to identify prenyltransferase inhibitors that displayed nanomolar affinity for RabGGTase and FTase. Detailed analysis of the two inhibitors revealed a complex inhibition mechanism in which their association with the peptide binding site of the enzyme reduces the enzyme's affinity for lipid and peptide substrates without competing directly with their binding. Finally, we demonstrate that the developed fluorescent isoprenoids can directly and efficiently penetrate into mammalian cells and be incorporated in vivo into small GTPases.
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Affiliation(s)
- Beatrice Dursina
- Max-Planck-Institute for Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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106
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Dunford JE, Rogers MJ, Ebetino FH, Phipps RJ, Coxon FP. Inhibition of protein prenylation by bisphosphonates causes sustained activation of Rac, Cdc42, and Rho GTPases. J Bone Miner Res 2006; 21:684-94. [PMID: 16734383 DOI: 10.1359/jbmr.060118] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
UNLABELLED N-BPs, which inhibit bone resorption by preventing prenylation of small GTPases, unexpectedly cause the accumulation of GTP-bound, unprenylated Rho family GTPases in macrophages and osteoclasts. In macrophages, this also leads to sustained, Rac-mediated activation of p38. The antiresorptive activity of N-BPs may therefore be caused at least in part, by the accumulation of unprenylated small GTPases, causing inappropriate activation of downstream signaling pathways. INTRODUCTION Nitrogen-containing bisphosphonates (N-BPs) are potent inhibitors of bone resorption that act by inhibiting farnesyl diphosphate synthase, thereby indirectly preventing the prenylation of Rho family GTPases that are required for the function and survival of bone-resorbing osteoclasts. However, the effect that these drugs have on the activity of Rho family GTPases has not been determined. MATERIALS AND METHODS The effect of N-BPs on the activity of Rho family GTPases in J774 macrophages and osteoclasts was measured using a pull-down assay to isolate the GTP-bound forms. The effect of N-BPs, or decreasing Rac expression using siRNA, on downstream p38 activity was evaluated by Western blotting and apoptosis assessed by measurement of caspase 3/7 activity. RESULTS Rather than inhibiting GTPase function, loss of prenylation after treatment with N-BPs caused an increase in the GTP-bound form of Rac, Cdc42, and Rho in J774 cells and osteoclast-like cells, which paralleled the rate of accumulation of unprenylated small GTPases. Activation of Rac also occurred with other inhibitors of prenylation of Rho-family proteins, such as mevastatin and the geranylgeranyl transferase I inhibitor GGTI-298. The Rac-GTP that increased after N-BP treatment was newly translated, cytoplasmic unprenylated protein, because it was not labeled with [(14)C] mevalonate, and the increase in Rac-GTP was prevented by cycloheximide. Furthermore, this unprenylated Rac-GTP retained at least part of its functional activity in J774 cells, because it mediated N-BP-induced activation of p38. Paradoxically, although risedronate induces apoptosis of J774 macrophages by inhibiting protein prenylation, the p38 inhibitor SB203580 enhanced N-BP-induced apoptosis, suggesting that Rac-induced p38 activation partially suppresses the pro-apoptotic effect of N-BPs in these cells. CONCLUSIONS N-BP drugs may disrupt the function of osteoclasts in vivo and affect other cell types in vitro by inhibiting protein prenylation, thereby causing inappropriate and sustained activation, rather than inhibition, of some small GTPases and their downstream signaling pathways.
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Affiliation(s)
- James E Dunford
- Bone Research Group, Institute of Medical Sciences, University of Aberdeen, Foresterhill, UK
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107
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Leung KF, Baron R, Seabra MC. Thematic review series: Lipid Posttranslational Modifications. Geranylgeranylation of Rab GTPases. J Lipid Res 2006; 47:467-75. [PMID: 16401880 DOI: 10.1194/jlr.r500017-jlr200] [Citation(s) in RCA: 188] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Rab GTPases require special machinery for protein prenylation, which include Rab escort protein (REP) and Rab geranylgeranyl transferase (RGGT). The current model of Rab geranylgeranylation proposes that REP binds Rab and presents it to RGGT. After geranylgeranylation of Rab C-terminal cysteines, REP delivers the prenylated protein to membranes. The REP-like protein Rab GDP dissociation inhibitor (RabGDI) then recycles the prenylated Rab between the membrane and the cytosol. The recent solution of crystal structures of the Rab prenylation machinery has helped to refine this model and provided further insights. The hydrophobic prenyl binding pocket of RGGT and geranylgeranyl transferase type-I (GGT-I) differs from that of farnesyl transferase (FT). A bulky tryptophan residue in FT restricts the size of the pocket, whereas in RGGT and GGT-I, this position is occupied by smaller residues. A highly conserved phenylalanine in REP, which is absent in RabGDI, is critical for the formation of the REP:RGGT complex. Finally, a geranylgeranyl binding site conserved in REP and RabGDI has been identified within helical domain II. The postprenylation events, including the specific targeting of Rabs to target membranes and the requirement for single versus double geranylgeranylation by different Rabs, remain obscure and should be the subject of future studies.
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Affiliation(s)
- Ka Fai Leung
- Molecular and Cellular Medicine, Division of Biomedical Sciences, Imperial College London, London SW7 2AZ, UK
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108
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Zhao H, Väänänen HK. Pharmacological sequestration of intracellular cholesterol in late endosomes disrupts ruffled border formation in osteoclasts. J Bone Miner Res 2006; 21:456-65. [PMID: 16491294 DOI: 10.1359/jbmr.051204] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2005] [Revised: 10/28/2005] [Accepted: 12/12/2005] [Indexed: 11/18/2022]
Abstract
UNLABELLED We showed that the ruffled border lacks a late endosomal lipid, LBPA, but is enriched incholesterol. A hydrophobic amine, U18666A, causes cholesterol accumulation in LBPA+ late endosomes in osteoclasts. Specific targeting of cathepsin K and the vacuolar H+-ATPase at the ruffled border is blocked by U18666A. A membrane trafficking pathway from baso-lateral membrane toward the resorptive organelle is also arrested by the inhibitor. These results indicate cholesterol homeostasis regulates late endosomal/lysosomal trafficking and polarized secretion in resorbing osteoclasts. INTRODUCTION Protons and acidic proteases are secreted into the resorption lacuna through the ruffled border to solubilize bone mineral and digest the organic bone matrix, respectively. Whereas evidence suggests this event occurs through a vesicular trafficking mechanism, this issue remains unresolved. MATERIALS AND METHODS The distribution of lysobisphosphatidic acid (LBPA) and cholesterol in resorbing osteoclasts was examined by laser scanning confocal microscopy. The effects of U18666A on ruffled border formation were observed by electron microscopy. RESULTS AND CONCLUSIONS The ruffled border does not contain LBPA but is enriched in cholesterol. We found a hydrophobic amine, U18666A, which blocks the efflux of cholesterol from late endosomes in other cells, causes cholesterol accumulation in LBPA-containing late endosomes in osteoclasts, leading to diminished cholesterol at the ruffled border. Reflecting the U18666A-mediated inhibition of late endosome/lysosome transport, the resorptive membrane is disrupted and contains a paucity of cathepsin K and the vacuolar H+-ATPase. These results indicate that the ruffled border is formed by the fusion of lysosomes with the plasma membrane in osteoclasts through a process that is cholesterol regulated.
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Affiliation(s)
- Haibo Zhao
- Department of Anatomy, Institute of Biomedicine, University of Turku, Turku, Finland.
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109
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Thompson K, Rogers MJ, Coxon FP, Crockett JC. Cytosolic Entry of Bisphosphonate Drugs Requires Acidification of Vesicles after Fluid-Phase Endocytosis. Mol Pharmacol 2006; 69:1624-32. [PMID: 16501031 DOI: 10.1124/mol.105.020776] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Bisphosphonates such as alendronate and zoledronate are blockbuster drugs used to inhibit osteoclast-mediated bone resorption. Although the molecular mechanisms by which bisphosphonates affect osteoclasts are now evident, the exact route by which they are internalized by cells is not known. To clarify this, we synthesized a novel, fluorescently labeled analog of alendronate (AF-ALN). AF-ALN was rapidly internalized into intracellular vesicles in J774 macrophages and rabbit osteoclasts; uptake of AF-ALN or [14C]zoledronate was stimulated by the presence of Ca2+ and Sr2+ and could be inhibited by addition of EGTA or clodronate, both of which chelate calcium ions. Both EGTA and clodronate also prevented the bisphosphonate-induced inhibition of Rap1A prenylation, an effect that was reversed by addition of Ca2+. In J774 cells and osteoclasts, vesicular AF-ALN colocalized with dextran (but not wheat germ agglutinin or transferrin), and uptake of AF-ALN or [14C]zoledronate was inhibited by dansylcadaverine, indicating that fluid-phase endocytosis is involved in the initial internalization of bisphosphonate into vesicles. Endosomal acidification then seems to be absolutely required for exit of bisphosphonate from vesicles and entry into the cytosol, because monensin and bafilomycin A1, both inhibitors of endosomal acidification, did not inhibit vesicular uptake of AF-ALN or internalization of [14C]zoledronate but prevented the inhibitory effect of alendronate or zoledronate on Rap1A prenylation. Taken together, these results demonstrate that cellular uptake of bisphosphonate drugs requires fluid-phase endocytosis and is enhanced by Ca2+ ions, whereas transfer from endocytic vesicles into the cytosol requires endosomal acidification.
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Affiliation(s)
- Keith Thompson
- Bone Research Group, Department of Medicine and Therapeutics, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen AB252ZD, UK
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110
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Roelofs AJ, Hulley PA, Meijer A, Ebetino FH, Russell RGG, Shipman CM. Selective inhibition of Rab prenylation by a phosphonocarboxylate analogue of risedronate induces apoptosis, but not S-phase arrest, in human myeloma cells. Int J Cancer 2006; 119:1254-61. [PMID: 16619218 DOI: 10.1002/ijc.21977] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Bisphosphonates (BPs) are widely used in the treatment of osteolytic bone disease associated with multiple myeloma, and have been demonstrated to exert antitumor effects both in vitro and in vivo. However, the precise molecular mechanisms involved in the direct antitumor effects of BPs in vitro are not known. Nitrogen-containing BPs, such as risedronate (RIS), act by inhibiting protein prenylation. A phosphonocarboxylate analogue of RIS, 3-PEHPC, has previously been shown in osteoclasts and macrophages to specifically inhibit prenylation of Rab GTPases. The aim of this study was to identify the molecular targets of RIS and 3-PEHPC in human myeloma cells and to determine the cellular effects of selective inhibition of Rab prenylation by 3-PEHPC as compared to nonspecific inhibition of protein prenylation by RIS in human myeloma cells. RIS dose-dependently inhibited prenylation of both Rap1A and Rab6, whereas 3-PEHPC only inhibited Rab6 prenylation. Both RIS and 3-PEHPC dose-dependently increased apoptosis in human myeloma cells. RIS induced an accumulation of cells in the S-phase of the cell cycle, associated with inhibition of DNA replication. In contrast, 3-PEHPC did not cause cell-cycle arrest. Furthermore, geranylgeraniol could prevent inhibition of prenylation, induction of apoptosis, and cell-cycle arrest in response to RIS, but not inhibition of Rab prenylation and apoptosis induced by 3-PEHPC, consistent with specific inhibition of Rab geranylgeranyl transferase by 3-PEHPC. In conclusion, our studies demonstrate that selective inhibition of Rab prenylation induces apoptosis, but not S-phase arrest, thus identifying distinct molecular pathways that mediate the antimyeloma effect of nitrogen-containing BPs.
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Affiliation(s)
- Anke J Roelofs
- Botnar Research Centre, Nuffield Orthopaedic Centre, University of Oxford, Oxford, United Kingdom
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111
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Thompson K, Rojas-Navea J, Rogers MJ. Alkylamines cause Vgamma9Vdelta2 T-cell activation and proliferation by inhibiting the mevalonate pathway. Blood 2005; 107:651-4. [PMID: 16179378 DOI: 10.1182/blood-2005-03-1025] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Three general classes of small, nonpeptide "antigens" activate Vgamma9Vdelta2 T cells: pyrophosphomonoesters, such as isopentenyl diphosphate (IPP), nitrogen-containing bisphosphonates (N-BPs), and alkylamines. However, we have shown recently that N-BPs indirectly activate Vgamma9Vdelta2 T cells as a consequence of inhibition of farnesyl diphosphate synthase (a key enzyme of the mevalonate pathway) and the intracellular accumulation of IPP. We now show that alkylamines activate Vgamma9Vdelta2 T cells by the same mechanism. Alkylamines were found to be weak inhibitors of farnesyl diphosphate synthase and caused accumulation of unprenylated Rap1A in peripheral blood mononuclear cells and macrophages, indicative of inhibition of the mevalonate pathway. Furthermore, as with N-BPs, the stimulatory effect of the alkylamines on Vgamma9Vdelta2T cells was abrogated by simultaneous treatment with mevastatin. These findings suggest that only pyrophosphomonoesters such as IPP are true Vgamma9Vdelta2 T-cell agonists, whereas alkylamines and N-BPs indirectly activate Vgamma9Vdelta2 T cells through a common mechanism involving the accumulation of IPP.
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Affiliation(s)
- Keith Thompson
- Bone Research Group, Department of Medicine and Therapeutics, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom.
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112
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Chen C, Dickman MB. cAMP blocks MAPK activation and sclerotial development via Rap-1 in a PKA-independent manner in Sclerotinia sclerotiorum. Mol Microbiol 2005; 55:299-311. [PMID: 15612936 DOI: 10.1111/j.1365-2958.2004.04390.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sclerotinia sclerotiorum is a filamentous ascomycete phytopathogen able to infect an extremely wide range of cultivated plants. Our previous studies have shown that increases in cAMP levels result in the impairment of the development of the sclerotium, a highly differentiated structure important in the disease cycle of this fungus. cAMP also inhibits the activation of a S. sclerotiorum mitogen-activated protein kinase (MAPK), which we have previously shown to be required for sclerotial maturation; thus cAMP-mediated sclerotial inhibition is modulated through MAPK. However, the mechanism(s) by which cAMP inhibits MAPK remains unclear. Here we demonstrate that a protein kinase A (PKA)-independent signalling pathway probably mediates MAPK inhibition by cAMP. Expression of a dominant negative form of Ras, an upstream activator of the MAPK pathway, also inhibited sclerotial development and MAPK activation, suggesting that a conserved Ras/MAPK pathway is required for sclerotial development. Evidence from bacterial toxins that specifically inhibit the activity of small GTPases, suggested that Rap-1 or Ras is involved in cAMP action. The Rap-1 inhibitor, GGTI-298, restored MAPK activation in the presence of cAMP, further suggesting that Rap-1 is responsible for cAMP-dependent MAPK inhibition. Importantly, inhibition of Rap-1 is able to restore sclerotial development blocked by cAMP. Our results suggest a novel mechanism involving the requirement of Ras/MAPK pathway for sclerotial development that is negatively regulated by a PKA-independent cAMP signalling pathway. Cross-talk between these two pathways is mediated by Rap-1.
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Affiliation(s)
- Changbin Chen
- Department of Plant Pathology, University of Nebraska-Lincoln, Nebraska, NE 68583, USA
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113
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Coxon FP, Ebetino FH, Mules EH, Seabra MC, McKenna CE, Rogers MJ. Phosphonocarboxylate inhibitors of Rab geranylgeranyl transferase disrupt the prenylation and membrane localization of Rab proteins in osteoclasts in vitro and in vivo. Bone 2005; 37:349-58. [PMID: 16006204 DOI: 10.1016/j.bone.2005.04.021] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Revised: 03/04/2005] [Accepted: 04/22/2005] [Indexed: 11/29/2022]
Abstract
Nitrogen-containing bisphosphonate drugs such as risedronate act by inhibiting farnesyl diphosphate synthase, thereby disrupting protein prenylation in osteoclasts. We recently found that an anti-resorptive phosphonocarboxylate analogue of risedronate, 3-PEHPC (previously referred to as NE10790), selectively prevents prenylation of Rab GTPases in vitro by specifically inhibiting Rab geranylgeranyl transferase. In this study, we demonstrate that unprenylated Rab6 could be detected in J774 cells after treatment with 3-PEHPC or risedronate for as little as 4 h, and reached 50% after 24 h. Furthermore, treatment of J774 cells or osteoclasts with either 3-PEHPC or risedronate disrupted membrane association of several Rab family proteins. Like risedronate, the effects of 3-PEHPC are likely to be restricted to osteoclasts in vivo, since both risedronate and 3-PEHPC inhibited Rab prenylation in osteoclasts, but not in general bone marrow cells, when administered to rabbits in vivo. Analysis of two new phosphonocarboxylate analogues of 3-PEHPC (3-PEPC and 2-PEPC) revealed that, first, the geminal hydroxyl group is not essential for inhibition of Rab prenylation by phosphonocarboxylates, but does contribute to their anti-resorptive potency, most likely by enhancing their affinity for bone mineral. Second, the position of the nitrogen in the side chain of phosphonocarboxylates is crucial for their ability to inhibit Rab prenylation and hence to inhibit bone resorption. In addition, there is a good correlation between the ability of the phosphonocarboxylates to inhibit Rab prenylation and to inhibit bone resorption in vitro, indicating that these compounds are a new class of pharmacological agents that inhibit bone resorption by specifically preventing prenylation of Rab proteins. Furthermore, although phosphonocarboxylates are analogues of bisphosphonates, the structure-activity relationships of phosphonocarboxylates for inhibiting Rab geranylgeranyltransferase appear to differ from the structure-activity relationships of bisphosphonates for inhibiting farnesyl diphosphate synthase.
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Affiliation(s)
- Fraser P Coxon
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
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114
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Pavlos NJ, Xu J, Riedel D, Yeoh JSG, Teitelbaum SL, Papadimitriou JM, Jahn R, Ross FP, Zheng MH. Rab3D regulates a novel vesicular trafficking pathway that is required for osteoclastic bone resorption. Mol Cell Biol 2005; 25:5253-69. [PMID: 15923639 PMCID: PMC1140603 DOI: 10.1128/mcb.25.12.5253-5269.2005] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Rab3 proteins are a subfamily of GTPases, known to mediate membrane transport in eukaryotic cells and play a role in exocytosis. Our data indicate that Rab3D is the major Rab3 species expressed in osteoclasts. To investigate the role of Rab3D in osteoclast physiology we examined the skeletal architecture of Rab3D-deficient mice and found an osteosclerotic phenotype. Although basal osteoclast number in null animals is normal the total eroded surface is significantly reduced, suggesting that the resorptive defect is due to attenuated osteoclast activity. Consistent with this hypothesis, ultrastructural analysis reveals that Rab3D(-/-) osteoclasts exhibit irregular ruffled borders. Furthermore, while overexpression of wild-type, constitutively active, or prenylation-deficient Rab3D has no significant effects, overexpression of GTP-binding-deficient Rab3D impairs bone resorption in vitro. Finally, subcellular localization studies reveal that, unlike wild-type or constitutively active Rab3D, which associate with a nonendosomal/lysosomal subset of post-trans-Golgi network (TGN) vesicles, inactive Rab3D localizes to the TGN and inhibits biogenesis of Rab3D-bearing vesicles. Collectively, our data suggest that Rab3D modulates a post-TGN trafficking step that is required for osteoclastic bone resorption.
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Affiliation(s)
- Nathan J Pavlos
- Unit of Orthopaedics, School of Surgery and Pathology, University of Western Australia, 2nd Floor M Block, QEII Medical Centre, Nedlands, Perth, Western Australia 6009, Australia
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115
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Lackner MR, Kindt RM, Carroll PM, Brown K, Cancilla MR, Chen C, de Silva H, Franke Y, Guan B, Heuer T, Hung T, Keegan K, Lee JM, Manne V, O'Brien C, Parry D, Perez-Villar JJ, Reddy RK, Xiao H, Zhan H, Cockett M, Plowman G, Fitzgerald K, Costa M, Ross-Macdonald P. Chemical genetics identifies Rab geranylgeranyl transferase as an apoptotic target of farnesyl transferase inhibitors. Cancer Cell 2005; 7:325-36. [PMID: 15837622 DOI: 10.1016/j.ccr.2005.03.024] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Revised: 11/05/2004] [Accepted: 03/23/2005] [Indexed: 10/25/2022]
Abstract
A chemical genetics approach identified a cellular target of several proapoptotic farnesyl transferase inhibitors (FTIs). Treatment with these FTIs caused p53-independent apoptosis in Caenorhabditis elegans, which was mimicked by knockdown of endosomal trafficking proteins, including Rab5, Rab7, the HOPS complex, and notably the enzyme Rab geranylgeranyl transferase (RabGGT). These FTIs were found to inhibit mammalian RabGGT with potencies that correlated with their proapoptotic activity. Knockdown of RabGGT induced apoptosis in mammalian cancer cell lines, and both RabGGT subunits were overexpressed in several tumor tissues. These findings validate RabGGT, and by extension endosomal function, as a therapeutically relevant target for modulation of apoptosis, and enhance our understanding of the mechanism of action of FTIs.
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Affiliation(s)
- Mark R Lackner
- Exelixis Inc., 170 Harbor Way, South San Francisco, California 94083, USA
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116
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Woo JT, Nakagawa H, Krecic AM, Nagai K, Hamilton AD, Sebti SM, Stern PH. Inhibitory effects of mevastatin and a geranylgeranyl transferase I inhibitor (GGTI-2166) on mononuclear osteoclast formation induced by receptor activator of NF kappa B ligand (RANKL) or tumor necrosis factor-alpha (TNF-alpha). Biochem Pharmacol 2005; 69:87-95. [PMID: 15588717 DOI: 10.1016/j.bcp.2004.08.036] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Accepted: 08/25/2004] [Indexed: 11/20/2022]
Abstract
We have previously reported that the statin mevastatin (compactin) reversibly inhibits the fusion of TRAP-positive mononuclear preosteoclasts (pOCs) into multinucleated osteoclasts and disrupts the actin ring in mature osteoclasts through the inhibition of protein prenylation. Protein geranylgeranylation, specifically, is known to be required for pOC fusion and for the function and survival of mature osteoclasts. However, it has not been determined whether protein geranylgeranylation is involved in early differentiation of osteoclasts (pOC formation). The current study shows that statins and the geranylgeranyl transferase I inhibitor GGTI-2166 inhibit the pOC formation induced by RANKL or TNF-alpha in cultures of both mouse marrow-derived macrophage-colony-stimulating factor (M-CSF) dependent monocytes (MD cells) and the mouse monocyte cell line RAW 264.7 (RAW cells). Mevastatin, 0.1-0.6 microM, inhibited the formation of pOCs induced by receptor activator of nuclear factor-kappaB ligand (RANKL) or tumor necrosis factor (TNF-alpha) in both cell cultures. The inhibitory effects of mevastatin were overcome by the addition of mevalonate, farnesyl pyrophosphate or geranylgeranyl pyrophosphate. GGTI-2166 inhibited TRAP activity induced by RANKL or TNF-alpha in both cell cultures and prevented the incorporation of [3H]all-trans geranylgeraniol into prenylated proteins in RAW cells. However, the farnesyl transferase inhibitor FTI-2153 did not inhibit TRAP activity although FTI prevented the incorporation of [14C]mevalonate into farnesylated proteins in RAW cells. Clostridium difficile cytotoxin B (toxin B) inhibited pOC formation induced by RANKL or TNF-alpha in both cell cultures. The inhibitory effects of statins and GGTI-2166 on pOC formation may result from the inhibition of the geranylgeranylation of G-proteins, such as Rho or Rac, suggesting that the geranylgeranylation of these proteins is involved in the early differentiation of progenitor cells into pOCs.
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Affiliation(s)
- Je-Tae Woo
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, 303 E. Chicago Avenue, Chicago, IL 60611, USA
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117
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Rogers MJ. From molds and macrophages to mevalonate: a decade of progress in understanding the molecular mode of action of bisphosphonates. Calcif Tissue Int 2004; 75:451-61. [PMID: 15332174 DOI: 10.1007/s00223-004-0024-1] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Accepted: 04/17/2004] [Indexed: 02/07/2023]
Abstract
Although bisphosphonates were first used as therapeutic agents to inhibit bone resorption in the early 1970s, their mode of action at the molecular level has only become fully clear within the last few years. One of the reasons for this lack of understanding was the difficulty in isolating large numbers of pure osteoclasts for biochemical studies. In the last decade, the identification of appropriate surrogate models that reflected the antiresorptive potencies of bisphosphonates, such as Dictyostelium slime molds and macrophages, helped overcome this problem and proved to be instrumental in elucidating the molecular pathways by which these compounds inhibit osteoclast-mediated bone resorption. This brief review summarizes our current understanding of these pathways.
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Affiliation(s)
- M J Rogers
- Bone Research Group, Institute of Medical Sciences, University of Aberdeen, AB25 2ZD, UK.
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118
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Durek T, Alexandrov K, Goody RS, Hildebrand A, Heinemann I, Waldmann H. Synthesis of Fluorescently Labeled Mono- and Diprenylated Rab7 GTPase. J Am Chem Soc 2004; 126:16368-78. [PMID: 15600338 DOI: 10.1021/ja046164n] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Modification of proteins with isoprenoid lipids is a widespread phenomenon in eukaryotic organisms that has received much attention due to its involvement in the progression of several diseases including cancer. Progress in studies of prenylated proteins has been hampered by difficulties associated with isolation of these proteins from native or recombinant sources. Small GTPases of the Rab family represent a particularly difficult example since they are doubly C-terminally geranylgeranylated and in some cases methylated. Here, we report an efficient and versatile strategy for the synthesis of mono- and digeranylgeranylated fluorescent RabGTPases using a combination of chemical synthesis and expressed protein ligation. Using this approach we generated fluorescent mono- and diprenylated Rab7 proteins that display near-native properties and form stoichiometric complexes with their natural chaperone REP-1. We demonstrate that the complex formed from semisynthetic monoprenylated Rab7 and REP-1 represents a genuine intermediate of the Rab prenylation reaction and thus provides a unique tool for studies of the Rab prenylation mechanism. Semisynthetic Rab7 proteins were used to develop a novel fluorescence-based in vitro prenylation assay. Using this assay we dissected the mechanism of the Rab7 double-geranylgeranylation reaction mediated by Rab geranylgeranyl transferase. We conclude that the reaction follows a random sequential mechanism. These results highlight the usefulness of the semisynthetic reaction intermediates in the study of protein posttranslational modification.
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Affiliation(s)
- Thomas Durek
- Max-Planck-Institut für Molekulare Physiologie, Abteilung Physikalische Biochemie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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119
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Minutolo F, Asso V, Bertini S, Betti L, Gervasi G, Ghilardi E, Giannaccini G, Placanica G, Prota G, Rapposelli S, Macchia M. Stable propylphosphonic acid analogues of geranylgeranyl diphosphate possessing inhibitory activity on geranylgeranyl protein transferase. ACTA ACUST UNITED AC 2004; 59:857-61. [PMID: 15544789 DOI: 10.1016/j.farmac.2004.06.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2004] [Accepted: 06/26/2004] [Indexed: 12/01/2022]
Abstract
Stable analogues of geranylgeranyl diphosphate, possessing 3-(phosphono)propionamido moieties in the place of the metabolically unstable diphosphate portion, were prepared and submitted to prenyltransferase (GGTase and FTase) inhibition assays. In one case, an excellent GGTase inhibitory activity was obtained (IC(50) = 39 nM), accompanied by a certain degree of GGTase vs. FTase selectivity.
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Affiliation(s)
- Filippo Minutolo
- Dipartimento di Scienze Farmaceutiche, Università di Pisa, Via Bonanno 6, 56126 Pisa, Italy
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120
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Minutolo F, Bertini S, Betti L, Danesi R, Gervasi G, Giannaccini G, Papi C, Placanica G, Barontini S, Rapposelli S, Macchia M. Stable analogues of geranylgeranyl diphosphate possessing improved geranylgeranyl versus farnesyl protein transferase inhibitory selectivity. Bioorg Med Chem Lett 2004; 13:4405-8. [PMID: 14643335 DOI: 10.1016/j.bmcl.2003.09.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Phosphonoacetamido(oxy) groups have proven to be good mimics of the diphosphate portion in geranylgeranyl protein transferase I (GGTase I) inhibitors. The introduction of small alkyl groups (Me, Et) into the diphosphate mimic moiety caused a further decrease in collateral farnesyl protein transferase (FTase) inhibitory activity, thereby improving GGTase I over FTase selectivity.
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Affiliation(s)
- Filippo Minutolo
- Dipartimento di Scienze Farmaceutiche, Università di Pisa, Via Bonanno 6, 56126 Pisa, Italy
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121
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El Oualid F, Burm BEA, Leroy IM, Cohen LH, van Boom JH, van den Elst H, Overkleeft HS, van der Marel GA, Overhand M. Design, Synthesis, and Evaluation of Su- gar Amino Acid Based Inhibitors of Pro- tein Prenyl Transferases PFT and PGGT-1. J Med Chem 2004; 47:3920-3. [PMID: 15267228 DOI: 10.1021/jm049927q] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Eleven analogues of the C-terminal Ca(1)a(2)X motif found in natural substrates of the prenyl transferases PFT and PGGT-1 were synthesized and evaluated for their inhibition potency and selectivity against PFT and PGGT-1. Replacement of the central dipeptide part a(1)a(2) by a benzylated sugar amino acid resulted in a good and highly selective PFT inhibitor (8, IC(50) = 250 +/- 20 nM). The methyl ester of 8 (13) selectively inhibited protein farnesylation in cultured cells.
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Affiliation(s)
- Farid El Oualid
- Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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122
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Huang CC, You JL, Wu MY, Hsu KS. Rap1-induced p38 Mitogen-activated Protein Kinase Activation Facilitates AMPA Receptor Trafficking via the GDI·Rab5 Complex. J Biol Chem 2004; 279:12286-92. [PMID: 14709549 DOI: 10.1074/jbc.m312868200] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Recent evidence has emphasized the importance of p38 mitogen-activated protein kinase (MAPK) in the induction of metabotropic glutamate receptor (mGluR)-dependent long term depression (LTD) at hippocampal CA3-CA1 synapses. However, the cascade responsible of mGluR to activate p38 MAPK and the signaling pathway immediately downstream from it to induce synaptic depression is poorly understood. Here, we show that transient activation of group I mGluR with the selective agonist (S)-3,5-dihydroxyphenylglycine (DHPG) activates p38 MAPK through G protein betagamma-subunit, small GTPase Rap1, and MAPK kinase 3/6 (MKK3/6), thus resulting in mGluR5-dependent LTD. Furthermore, our data clearly show that an accelerating AMPA receptor endocytosis by stimulating the formation of guanyl nucleotide dissociation inhibitor-Rab5 complex is a potential downstream processing of p38 MAPK activation to mediate DHPG-LTD. These results suggest an important role for Rap1-MKK3/6-p38 MAPK pathway in the induction of mGluR-dependent LTD by directly coupling to receptor trafficking machineries to facilitate the loss of synaptic AMPA receptors.
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Affiliation(s)
- Chiung-Chun Huang
- Department of Pharmacology, College of Medicine, National Cheng Kung University, No. 1 University Road, Tainan City 701, Taiwan
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123
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Thompson K, Rogers MJ. Statins prevent bisphosphonate-induced gamma,delta-T-cell proliferation and activation in vitro. J Bone Miner Res 2004; 19:278-88. [PMID: 14969398 DOI: 10.1359/jbmr.0301230] [Citation(s) in RCA: 164] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2003] [Revised: 09/16/2003] [Accepted: 09/17/2003] [Indexed: 11/18/2022]
Abstract
UNLABELLED The acute phase response is the major adverse effect of intravenously administered N-BPs. In this study we show that N-BPs cause gamma,delta-T-cell activation and proliferation in vitro by an indirect mechanism through inhibition of FPP synthase, an effect that can be overcome by inhibiting HMG-CoA reductase with a statin. These studies clarify the probable initial cause of the acute phase response to N-BP drugs and suggest a possible way of preventing this phenomenon. INTRODUCTION The acute phase response is the major adverse effect of intravenously administered nitrogen-containing bisphosphonate drugs (N-BPs), used in the treatment of metabolic bone diseases. This effect has recently been attributed to their action as non-peptide antigens and direct stimulation of gamma,delta-T-cells. However, because N-BPs are potent inhibitors of farnesyl diphosphate (FPP) synthase, they could cause indirect activation of gamma,delta-T-cells owing to the accumulation of intermediates upstream of FPP synthase in the mevalonate pathway, such as isopentenyl diphosphate/dimethylallyl diphosphate, which are known gamma,delta-T-cell agonists. MATERIALS AND METHODS Peripheral blood mononuclear cells (PBMCs) were isolated from healthy volunteers and treated with N-BP, statin, or intermediates/inhibitors of the mevalonate pathway for 7 days in the presence of interleukin (IL)-2. Flow cytometric analysis of the T-cell-gated population was used to quantify the proportion of gamma,delta-T-cells in the CD3+ population. RESULTS AND CONCLUSIONS The ability of N-BPs to stimulate proliferation of CD3+ gamma,delta-T-cells in human PBMC cultures matched the ability to inhibit FPP synthase. Gamma,delta-T-cell proliferation and activation (interferon gamma [IFNgamma] and TNFalpha release) was prevented by mevastatin or lovastatin, which inhibit HMG-CoA reductase upstream of FPP synthase and prevent the synthesis of isopentenyl diphosphate/dimethylallyl diphosphate. Desoxolovastatin, an analog of lovastatin incapable of inhibiting HMG-CoA reductase, did not overcome the stimulatory effect of N-BP. Furthermore, statins did not prevent the activation of gamma,delta-T-cells by a synthetic gamma,delta-T-cell agonist or by anti-CD3 antibody. Together, these observations show that N-BPs indirectly stimulate the proliferation and activation of gamma,delta-T-cells caused by inhibition of FPP synthase and intracellular accumulation of isopentenyl diphosphate/ dimethylallyl diphosphate in PBMCs. Because activation of gamma,delta-T-cells could be the initiating event in the acute phase response to bisphosphonate therapy, co-administration of a statin could be an effective approach to prevent this adverse effect.
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Affiliation(s)
- Keith Thompson
- Bone Research Group, Department of Medicine and Therapeutics, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom.
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124
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van Beek ER, Cohen LH, Leroy IM, Ebetino FH, Löwik CWGM, Papapoulos SE. Differentiating the mechanisms of antiresorptive action of nitrogen containing bisphosphonates. Bone 2003; 33:805-11. [PMID: 14623056 DOI: 10.1016/j.bone.2003.07.007] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Bisphosphonates (BPS) inhibit bone resorption and are divided into two classes according to their chemical structure and mechanism of action: nonnitrogen containing BPS such as etidronate and clodronate that are of low potency and inhibit osteoclast function via metabolism into toxic ATP-metabolites and nitrogen-containing BPS (NBPS), such as alendronate and risedronate that inhibit the enzyme of the mevalonate biosynthetic pathway farnesyl pyrophosphate synthase (FPPS), resulting in inhibition of the prenylation of small GTP-binding proteins in osteoclasts and disruption of their cytoskeleton. Previously, studies in various cell types suggested, however, that pamidronate functions by mechanism(s) additional or independent of the mevalonate pathway. To examine if such mechanism(s) are also involved in the action of NBPS on osteoclastic bone resorption, we examined the action of alkyl and heterocyclic NBPS with close structural homology on FPPS/isopentenyl pyrophosphate isomerase (IPPI) activity, on osteoclastic resorption, and on reversibility of this effect with GGOH. As expected, both pamidronate and alendronate suppressed bone resorption and FPPS/IPPI activity, the latter with greater potency than the first. Surprisingly, however, unlike alendronate, the antiresorptive effect of pamidronate was only partially reversible with GGOH, indicating the involvement of mechanism(s) of action additional to that of suppression of FPPS. Comparable results were obtained with the heterocyclic NBP NE-21650, a structural analog of risedronate. Thus, despite an effect on FPPS, the actions on bone resorption of some NBPS may involve mechanisms additional to suppression of FPPS. These findings may lead to identification of additional pathways that are important for bone resorption and may help to differentiate among members of the NBP class which are currently distinguished only according to their potency to inhibit bone resorption.
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Affiliation(s)
- E R van Beek
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands.
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125
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Mulari M, Vääräniemi J, Väänänen HK. Intracellular membrane trafficking in bone resorbing osteoclasts. Microsc Res Tech 2003; 61:496-503. [PMID: 12879417 DOI: 10.1002/jemt.10371] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
There is ample evidence now that the two major events in bone resorption, namely dissolution of hydroxyapatite and degradation of the organic matrix, are performed by osteoclasts. The resorption cycle involves several specific cellular activities, where intracellular vesicular trafficking plays a crucial role. Although details of these processes started to open up only recently, it is clear that vesicular trafficking is needed in several specific steps of osteoclast functioning. Several plasma membrane domains are formed during the polarization of the resorbing cells. Multinucleated osteoclasts create a tight sealing to the extracellular matrix as a first indicator of their resorption activity. Initial steps of the sealing zone formation are alpha(v)beta(3)-integrin mediated, but the final molecular interaction(s) between the plasma membrane and mineralized bone matrix is still unknown. A large number of acidic intracellular vesicles then fuse with the bone-facing plasma membrane to form a ruffled border membrane, which is the actual resorbing organelle. The formation of a ruffled border is regulated by a small GTP-binding protein, rab7, which indicates the late endosomal character of the ruffled border membrane. Details of specific membrane transport processes in the osteoclasts, e.g., the formation of the sealing zone and transcytosis of bone degradation products from the resorption lacuna to the functional secretory domain remain to be clarified. It is tempting to speculate that specific features of vesicular trafficking may offer several potential new targets for drug therapy of bone diseases.
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Affiliation(s)
- Mika Mulari
- Department of Anatomy, Institute of Biomedicine, University of Turku, 20520 Turku, Finland
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126
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Salomo M, Jurlander J, Nielsen LB, Gimsing P. How myeloma cells escape bisphosphonate-mediated killing: development of specific resistance with preserved sensitivity to conventional chemotherapeutics. Br J Haematol 2003; 122:202-10. [PMID: 12846887 DOI: 10.1046/j.1365-2141.2003.04437.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Although amino-bisphosphonates (N-BPs) induce apoptosis of myeloma cells in vitro, most in-vivo studies fail to demonstrate a corresponding antitumour effect. This discrepancy might reflect the development of resistance to the antitumour effects of N-BP in myeloma cells when they are exposed to N-BP for a prolonged time. To test this hypothesis, two N-BP-sensitive human myeloma cell lines were continuously exposed to increasing concentrations of the N-BP alendronate for 6 weeks. During this treatment period, 10 out of 10 sublines developed reduced apoptotic and antiproliferative responses to alendronate treatment. This de novo alendronate resistance was accompanied by resistance to another N-BP (zoledronate) but not to an inhibitor of 3-hydroxy-3-methylglutaryl CoA reductase or Fas ligand. Importantly, N-BP-resistant myeloma cells also remained sensitive to conventional myeloma chemotherapeutics (melphalan, doxorubicin and vincristine). Further analysis of the N-BP-resistant cells revealed an increased activity of the N-BP-specific target enzyme farnesyl pyrophosphate synthase, without upregulation of its gene transcription. Our results suggest that continuous exposure of myeloma cells to alendronate leads to the development of N-BP resistance. This is associated with an increased activity of farnesyl pyrophosphate synthase and does not evolve from defective apoptotic pathways. Importantly, the antitumour effects of conventional myeloma chemotherapeutics are preserved in the N-BP-resistant myeloma cells.
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Affiliation(s)
- Morten Salomo
- Department of Haematology, University of Copenhagen, Denmark.
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127
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Frith JC, Rogers MJ. Antagonistic effects of different classes of bisphosphonates in osteoclasts and macrophages in vitro. J Bone Miner Res 2003; 18:204-12. [PMID: 12568397 DOI: 10.1359/jbmr.2003.18.2.204] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Nitrogen-containing bisphosphonates, such as alendronate and ibandronate, inhibit bone resorption by preventing protein prenylation in osteoclasts, whereas non-nitrogen-containing bisphosphonates, such as clodronate, are metabolized to nonhydrolyzable analogs of ATP, resulting in osteoclast apoptosis. Because these two classes of bisphosphonates have different molecular mechanisms of action, we examined in vitro whether combined treatment with clodronate and alendronate would alter antiresorptive effectiveness. Although, in cultures of rabbit osteoclasts, the antiresorptive effect of 10 microM alendronate was increased by the addition of clodronate, the effect of higher concentrations of alendronate was not altered by addition of clodronate. Furthermore, the inhibition of protein prenylation in osteoclasts caused by higher alendronate concentrations was partially prevented by cotreatment with clodronate. As in osteoclasts, the inhibition of protein prenylation in J774 cells caused by alendronate or ibandronate treatment was dose-dependently prevented by cotreatment with clodronate. Furthermore, alendronate-induced J774 apoptosis was significantly inhibited in the presence of clodronate. The presence of clodronate also decreased the short-term cellular uptake of [14C]ibandronate. These observations suggest that combined treatment with clodronate could enhance the antiresorptive effect of a low concentration of nitrogen-containing bisphosphonate, but clodronate can also antagonize some of the molecular actions and effects of higher concentrations of nitrogen-containing bisphosphonates. The exact molecular basis for the antagonistic effects between bisphosphonates remain to be determined, but could involve competition for cellular uptake by a membrane-bound transport protein.
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Affiliation(s)
- Julie C Frith
- Department of Medicine and Therapeutics, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom.
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Abstract
The nitrogen-containing bisphosphonates (N-BPs), alendronate and risedronate, are the only pharmacologic agents shown to prevent spine and nonvertebral fractures associated with postmenopausal and glucocorticoid-induced osteoporosis. At the tissue level, this is achieved through osteoclast inhibition, which leads to reduced bone turnover, increased bone mass, and improved mineralization. The molecular targets of bisphosphonates (BPs) have recently been identified. This review will discuss the mechanism of action of BPs, focusing on alendronate and risedronate, which are the two agents most widely studied. They act on the cholesterol biosynthesis pathway enzyme, farnesyl diphosphate synthase. By inhibiting this enzyme in the osteoclast, they interfere with geranylgeranylation (attachment of the lipid to regulatory proteins), which causes osteoclast inactivation. This mechanism is responsible for N-BP suppression of osteoclastic bone resorption and reduction of bone turnover, which leads to fracture prevention.
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Affiliation(s)
- Alfred A Reszka
- Department of Bone Biology and Osteoporosis Research, Merck Research Laboratories, West Point, PA 19486, USA
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129
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Sidorovitch V, Niculae A, Kan N, Ceacareanu AC, Alexandrov K. Expression of mammalian Rab Escort protein-1 and -2 in yeast Saccharomyces cerevisiae. Protein Expr Purif 2002; 26:50-8. [PMID: 12356470 DOI: 10.1016/s1046-5928(02)00506-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Rab GTPases are post-translationally geranylgeranylated on their C-terminal cysteines by Rab geranylgeranyl transferase (RabGGTase) and this modification is essential for their biological activity. Rab Escort Protein (REP) is a molecular chaperone that assists in the prenylation reaction carried out by RabGGTase. Mutations in the REP-1 gene lead to progressive retinal degradation and blindness in humans. Despite the significant interest in REP proteins, their preparative production remains challenging. We report here an inducible expression system for the production of REP-1 and REP-2 in yeast Saccharomyces cerevisiae at levels 3.5 and 2mg/L, respectively. The REP-1 was found to be toxic for yeast cells and its toxicity is proposed to be associated with the formation of unproductive Ypt:REP-1 complexes. To minimize the toxic effect of REP-1, the recombinant protein expression was induced at the end of the exponential phase. Under these conditions, the GAL1 promoter is no longer repressed due to exhaustion of glucose and utilization of ethanol as a carbon source. This expression procedure was successfully scaled up to 30L for both proteins. The REP-1 and REP-2 were purified using a combination of affinity and anion-exchange chromatography. Purified proteins were functionally active, as determined by a fluorescent Rab binding assay and in vitro prenylation. The reported procedure provides a reliable source of REP proteins for biochemical and structural studies.
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Affiliation(s)
- Vadim Sidorovitch
- Max-Plank-Institute for Molecular Physiology, Otto-Hahn-Str. 11, 44227, Dortmund, Germany
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El Oualid F, Bruining L, Leroy I, Cohen L, van Boom J, van der Marel G, Overkleeft H, Overhand M. Synthesis and Biological Evaluation of Protein:Geranylgeranyltransferase I Inhibitors Based on the CaaX Box: Incorporation of Sugar Amino Acids as Dipeptide Isosters. Helv Chim Acta 2002. [DOI: 10.1002/1522-2675(200210)85:10<3455::aid-hlca3455>3.0.co;2-#] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Farid El Oualid
- Leiden Institute of Chemistry, Gorlaeus Laboratories, P.O. Box 9502, NL‐2301 RA Leiden
| | - Leon Bruining
- Leiden Institute of Chemistry, Gorlaeus Laboratories, P.O. Box 9502, NL‐2301 RA Leiden
| | - Ingrid M. Leroy
- TNO Prevention and Health, Gaubius Laboratory, P.O. Box 2215, NL‐2301 CE Leiden
| | - Louis H. Cohen
- TNO Prevention and Health, Gaubius Laboratory, P.O. Box 2215, NL‐2301 CE Leiden
| | - Jacques H. van Boom
- Leiden Institute of Chemistry, Gorlaeus Laboratories, P.O. Box 9502, NL‐2301 RA Leiden
| | - Gijs A. van der Marel
- Leiden Institute of Chemistry, Gorlaeus Laboratories, P.O. Box 9502, NL‐2301 RA Leiden
| | - Herman S. Overkleeft
- Leiden Institute of Chemistry, Gorlaeus Laboratories, P.O. Box 9502, NL‐2301 RA Leiden
| | - Mark Overhand
- Leiden Institute of Chemistry, Gorlaeus Laboratories, P.O. Box 9502, NL‐2301 RA Leiden
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131
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Rak A, Reents R, Pylypenko O, Niculae A, Sidorovitch V, Thomä NH, Waldmann H, Schlichting I, Goody RS, Alexandrov K. Crystallization and preliminary X-ray diffraction analysis of the Rab escort protein-1 in complex with Rab geranylgeranyltransferase. J Struct Biol 2001; 136:158-61. [PMID: 11886217 DOI: 10.1006/jsbi.2001.4433] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Posttranslational prenylation of proteins is a widespread phenomenon and the majority of prenylated proteins are geranylgeranylated members of the Rab GTPase family. Geranylgeranylation is catalyzed by Rab geranylgeranyltransferase (RabGGTase) and is critical for the ability of Rab protein to mediate vesicular docking and fusion of various intracellular vesicles. RabGGTase consists of a catalytic alpha/beta heterodimer and an accessory protein termed Rab escort protein (REP-1) that delivers the newly prenylated Rab proteins to their target membrane. Mutations in the REP-1 gene in humans lead to an X-chromosome-linked defect known as choroideremia--a debilitating disease that inevitably culminates in complete blindness. Here we report in vitro assembly and purification of the stoichiometric ternary complex of RabGGTase with REP-1 stabilized by a hydrolysis-resistant phosphoisoprenoid analog--farnesyl phosphonyl(methyl)phoshonate. The complex formed crystals of extended plate morphology under low ionic-strength conditions. X-ray diffraction data were collected to 2.8 A resolution at the ESRF. The crystals belong to the monoclinic space group P2(1), with unit-cell parameters a = 68.7, b = 197.7, c = 86.1 A, beta = 113.4 degrees. Preliminary structural analysis revealed the presence of one molecule in the asymmetric unit.
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Affiliation(s)
- A Rak
- Max-Plank-Institute for Molecular Physiology, Dortmund, Germany
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