Nitrogen-Containing Bisphosphonates as Carbocation Transition State Analogs for Isoprenoid Biosynthesis

Martin, Michael; Arnold, William R.; Heath, Huel T.; Urbina, Julio A.; Oldfield, Eric

doi:10.1006/bbrc.1999.1404

Cited by 149 publications

(142 citation statements)

References 18 publications

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“…The recent generation of X-ray crystal structures of the human FPP synthase enzyme, cocrystallized with risedronate or zoledronic acid (17,18), revealed that N-BPs bind in the geranyl diphosphate (GPP) binding site of the enzyme, with stabilizing interactions occurring between the nitrogen moiety of the N-BP and a conserved threonine and lysine residue in the enzyme. This is consistent with the earlier suggestion by Oldfield et al (19) that N-BPs mimic the structure of the natural isoprenoid pyrophosphate substrates of the enzyme, GPP and dimethylallyl diphosphate, and compete for binding at the GPP/ dimethylallyl diphosphate substrate binding pocket. N-BPs also seem to inhibit bacterial FPP synthase in a similar manner (20).…”

Section: Nitrogen-containing Bisphosphonates Act By Inhibiting Farnessupporting

confidence: 93%

Molecular Mechanisms of Action of Bisphosphonates: Current Status

Roelofs

Thompson²,

Gordon³

et al. 2006

Clinical Cancer Research

503

412

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Purpose: Bisphosphonates are currently the most important class of antiresorptive agents used in the treatment of metabolic bone diseases, including tumor-associated osteolysis and hypercalcemia. These compounds have high affinity for calcium ions and therefore target bone mineral, where they are internalized by bone-resorbing osteoclasts and inhibit osteoclast function. Experimental Design: This article reviews the pharmacology of bisphosphonates and the relationship between chemical structure and antiresorptive potency. We also describe new insights into their intracellular molecular mechanisms of action, methods for assessing the effects of bisphosphonates on protein prenylation, and their potential as direct antitumor agents. Results: Nitrogen-containing bisphosphonates act intracellularly by inhibiting farnesyl diphosphate synthase, an enzyme of the mevalonate pathway, thereby preventing prenylation of small GTPase signaling proteins required for normal cellular function. Inhibition of farnesyl diphosphate synthase also seems to account for their antitumor effects observed in vitro and for the activation of g,y T cells, a feature of the acute-phase response to bisphosphonate treatment in humans. Bisphosphonates that lack a nitrogen in the chemical structure do not inhibit protein prenylation and have a different mode of action that seems to involve primarily the formation of cytotoxic metabolites in osteoclasts. Conclusions: Bisphosphonates are highly effective inhibitors of bone resorption that selectively affect osteoclasts in vivo but could also have direct effects on other cell types, such as tumor cells. After >30 years of clinical use, their molecular mechanisms of action on osteoclasts are finally becoming clear but their exact antitumor properties remain to be clarified.Bisphosphonates remain the most widely used and effective antiresorptive agents for the treatment of diseases in which there is an increase in the number or activity of osteoclasts, including tumor-associated osteolysis and hypercalcemia (1). This brief review summarizes our current understanding of the molecular mechanisms of action of bisphosphonates on osteoclasts and their potential to affect other cell types, such as tumor cells, via the same molecular mechanisms. General Properties of BisphosphonatesBisphosphonates are synthetic, nonhydrolyzable analogues of PP i (Fig. 1). The P-C-P structure of bisphosphonates imparts the ability to bind divalent metal ions, such as Ca 2+ (2). For this reason, bisphosphonates are rapidly cleared from the circulation (3, 4) and bind to bone mineral surfaces in vivo at sites of active bone remodeling, particularly areas undergoing osteoclastic resorption (5). The targeting of bisphosphonates to bone, localized release during osteoclastic bone resorption, and efficient uptake into osteoclasts by endocytosis explains why bisphosphonates seem to have a highly selective effect on osteoclasts (2). However, this does not exclude the possibility that small amounts of these drugs are internaliz...

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Section: Nitrogen-containing Bisphosphonates Act By Inhibiting Farnessupporting

confidence: 93%

Molecular Mechanisms of Action of Bisphosphonates: Current Status

Roelofs

Thompson²,

Gordon³

et al. 2006

Clinical Cancer Research

503

412

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“…icking the carbocation intermediate formed after substrate ionization (30). The structure of the FPPS IPP⅐risedronate ternary complex presented here confirms this suggestion and reveals how key enzyme residues, as well as IPP participate in inhibitor binding.…”

Section: Structures Of Fpps Substrate and Inhibitor Ternary Complexessupporting

confidence: 79%

Structural Basis for Bisphosphonate-mediated Inhibition of Isoprenoid Biosynthesis

Hosfield¹,

Zhang²,

Dougan³

et al. 2004

Journal of Biological Chemistry

252

351

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Farnesyl pyrophosphate synthetase (FPPS) synthesizes farnesyl pyrophosphate through successive condensations of isopentyl pyrophosphate with dimethylallyl pyrophosphate and geranyl pyrophosphate. Nitrogen-containing bisphosphonate drugs used to treat osteoclast-mediated bone resorption and tumor-induced hypercalcemia are potent inhibitors of the enzyme. Here we present crystal structures of substrate and bisphosphonate complexes of FPPS. The structures reveal how enzyme conformational changes organize conserved active site residues to exploit metal-induced ionization and substrate positioning for catalysis. The structures further demonstrate how nitrogen-containing bisphosphonates mimic a carbocation intermediate to inhibit the enzyme. Together, these FPPS complexes provide a structural template for the design of novel inhibitors that may prove useful for the treatment of osteoporosis and other clinical indications including cancer.Post-translational modification of C-terminal CAAX sequences by covalent attachment of isoprenyl chains is crucial for intracellular localization and proper function of small GTPases such as Ras, Rac, Rho, and CDC42 (1, 2). The substrates for these modifications are the 15-carbon isoprenoid farnesyl pyrophosphate (FPP) 1 or the 20-carbon isoprenoid geranyl-geranyl pyrophosphate synthesized by enzymes of the mevalonate pathway (3) (Fig. 1A). A key branch point enzyme of the mevalonate pathway is farnesyl pyrophosphate synthetase (FPPS), a ϳ30-kDa Mg 2ϩ -dependent homodimeric enzyme that synthesizes (E,E)-FPP from isopentyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) (4, 5) (Fig. 1B). Interest in understanding FPPS activity stems from the recent discovery that FPPS is the molecular target of nitrogencontaining bisphosphonates (6,7,31,32). Bisphophonates are non-cleavable pyrophosphate (P-O-P) analogues in which the central oxygen is replaced by a carbon (P-C-P) with various side chains (Fig. 1C). Against parasitic organisms (8, 9) these agents have been shown in vitro to disrupt cell growth through FPPS inhibition. In people, bisphosphonates are targeted to bone tissue (10) where FPPS inhibition in bone-resorbing osteoclasts is a current therapeutic approach for treating postmenopausal osteoporosis (11,12). Because of their bone-targeting properties, bisphosphonates have also found use as agents to treat tumor-induced hypercalcemia (13), Paget's disease (14), and osteolytic metastases (15).Although structures of apo-and ligand-bound avian FPPS have been solved (16,17), the active sites are unassembled and do not provide substantial information concerning catalysis. Thus, to resolve the molecular basis of catalysis, and also to understand the structural features governing bisphosphonate recognition, we determined the structures of unliganded Staphylococcus aureus FPPS (FPPS-Sa), as well as two Escherichia coli FPPS (FPPS-Ec) ternary complexes. These ternary complexes include a 2.4-Å "substrate-bound" structure containing IPP and the noncleavable DMAPP analogue dimethyla...

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“…81 These agents bind to the dimethylallyl/ geranyl pyrophosphate ligand pocket and induce a conformational change. The interactions of the N-bisphosphonate cyclic nitrogen with Thr201 and Lys200 suggest that these inhibitors achieve potency by positioning their nitrogen in a proposed carbocation 82 binding site. This explains how the nitrogen moiety is so important to the potency of these bisphosphonates.…”

Section: Figurementioning

confidence: 99%

Bisphosphonates: Mode of Action and Pharmacology

2007

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The profound effects of the bisphosphonates on calcium metabolism were discovered over 30 years ago, and they are now well established as the major drugs used for the treatment of bone diseases associated with excessive resorption. Their principal uses are for Paget disease of bone, myeloma, bone metastases, and osteoporosis in adults, but there has been increasing and successful application in pediatric bone diseases, notably osteogenesis imperfecta. Bisphosphonates are structural analogues of inorganic pyrophosphate but are resistant to enzymatic and chemical breakdown. Bisphosphonates inhibit bone resorption by selective adsorption to mineral surfaces and subsequent internalization by bone-resorbing osteoclasts where they interfere with various biochemical processes. The simpler, non-nitrogen-containing bisphosphonates (eg, clodronate and etidronate) can be metabolically incorporated into nonhydrolysable analogues of adenosine triphosphate (ATP) that may inhibit ATP-dependent intracellular enzymes. In contrast, the more potent, nitrogen-containing bisphosphonates (eg, pamidronate, alendronate, risedronate, ibandronate, and zoledronate) inhibit a key enzyme, farnesyl pyrophosphate synthase, in the mevalonate pathway, thereby preventing the biosynthesis of isoprenoid compounds that are essential for the posttranslational modification of small guanosine triphosphate (GTP)-binding proteins (which are also GTPases) such as Rab, Rho, and Rac. The inhibition of protein prenylation and the disruption of the function of these key regulatory proteins explains the loss of osteoclast activity. The recently elucidated crystal structure of farnesyl diphosphate reveals how bisphosphonates bind to and inhibit at the active site via their critical nitrogen atoms. Although bisphosphonates are now established as an important class of drugs for the treatment of many bone diseases, there is new knowledge about how they work and the subtle but potentially important differences that exist between individual bisphosphonates. Understanding these may help to explain differences in potency, onset and duration of action, and clinical effectiveness.www.pediatrics.org/cgi

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Nitrogen-Containing Bisphosphonates as Carbocation Transition State Analogs for Isoprenoid Biosynthesis

Cited by 149 publications

References 18 publications

Molecular Mechanisms of Action of Bisphosphonates: Current Status

Molecular Mechanisms of Action of Bisphosphonates: Current Status

Structural Basis for Bisphosphonate-mediated Inhibition of Isoprenoid Biosynthesis

Bisphosphonates: Mode of Action and Pharmacology

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