Mevalonate pathway orchestrates insulin signaling via RAB14 geranylgeranylation-mediated phosphorylation of AKT to regulate hepatic glucose metabolism.

Statin use accompanies with increased risk of new onset of type 2 diabetes, however, the underlying mechanisms remain not be fully understood and effective prevention strategies are still lacking. Herein, we find that both pharmacological and genetic inhibition of GGTase II mimic the disruption of simvastatin on hepatic insulin signaling and glucose metabolism in vitro. AAV8-mediated knockdown of liver RABGGTA, the specific subunit of GGTase II, triggers systemic glucose metabolism disorders in vivo. By adopting a small-scale siRNA screening, we identify RAB14 as a regulator of hepatic insulin signaling and glucose metabolism. Geranylgeranylation deficiency of RAB14 inhibits the phosphorylation of AKT (Ser473) and disrupts hepatic insulin signaling and glucose metabolism possibly via impeding mTORC2 complex assembly. Finally, geranylgeranyl pyrophosphate (GGPP) supplementation is sufficient to prevent simvastatin-caused disruption of hepatic insulin signaling and glucose metabolism in vitro. Geranylgeraniol (GGOH), a precursor of GGPP, is able to ameliorate simvastatin-induced systemic glucose metabolism disorders in vivo. In conclusion, our data indicate that statins-targeted mevalonate pathway regulates hepatic insulin signaling and glucose metabolism via geranylgeranylation of RAB14. GGPP/GGOH supplementation might be an effective strategy for the prevention of the diabetic effects of statins.

Synthesis and evaluation of cyclopentane-based muraymycin analogs targeting MraY.

Antibiotic resistance is one of the most challenging global health issues and presents an urgent need for the development of new antibiotics. In this regard, phospho-MurNAc-pentapeptide translocase (MraY), an essential enzyme in the early stages of peptidoglycan biosynthesis, has emerged as a promising new antibiotic target. We recently reported the crystal structures of MraY in complex with representative members of naturally occurring nucleoside antibiotics, including muraymycin D2. However, these nucleoside antibiotics are synthetically challenging targets, which limits the scope of medicinal chemistry efforts on this class of compounds. To gain access to active muraymycin analogs with reduced structural complexity and improved synthetic tractability, we prepared and evaluated cyclopentane-based muraymycin analogs for targeting MraY. For the installation of the 1,2-syn-amino alcohol group of analogs, the diastereoselective isocyanoacetate aldol reaction was explored. The structure-activity relationship analysis of the synthesized analogs suggested that a lipophilic side chain is essential for MraY inhibition. Importantly, the analog 20 (JH-MR-23) showed antibacterial efficacy against Staphylococcus aureus. These findings provide insights into designing new muraymycin-based MraY inhibitors with improved chemical tractability.

Exploring the Active Site of the Antibacterial Target MraY by Modified Tunicamycins.

The alarming growth of antibiotic resistance that is currently ongoing is a serious threat to human health. One of the most promising novel antibiotic targets is MraY (phospho-MurNAc-pentapeptide-transferase), an essential enzyme in bacterial cell wall synthesis. Through recent advances in biochemical research, there is now structural information available for MraY, and for its human homologue GPT (GlcNAc-1-P-transferase), that opens up exciting possibilities for structure-based drug design. The antibiotic compound tunicamycin is a natural product inhibitor of MraY that is also toxic to eukaryotes through its binding to GPT. In this work, we have used tunicamycin and modified versions of tunicamycin as tool compounds to explore the active site of MraY and to gain further insight into what determines inhibitor potency. We have investigated tunicamycin variants where the following motifs have been modified: the length and branching of the tunicamycin fatty acyl chain, the saturation of the fatty acyl chain, the 6″-hydroxyl group of the GlcNAc ring, and the ring structure of the uracil motif. The compounds are analyzed in terms of how potently they bind to MraY, inhibit the activity of the enzyme, and affect the protein thermal stability. Finally, we rationalize these results in the context of the protein structures of MraY and GPT.

Merging Natural Products: Muraymycin-Sansanmycin Hybrid Structures as Novel Scaffolds for Potential Antibacterial Agents.

To overcome bacterial resistances, the need for novel antimicrobial agents is urgent. The class of so-called nucleoside antibiotics furnishes promising candidates for the development of new antibiotics, as these compounds block a clinically unexploited bacterial target: the integral membrane protein MraY, a key enzyme in cell wall (peptidoglycan) biosynthesis. Nucleoside antibiotics exhibit remarkable structural diversity besides their uridine-derived core motifs. Some sub-classes also show specific selectivities towards different Gram-positive and Gram-negative bacteria, which are poorly understood so far. Herein, the synthesis of a novel hybrid structure is reported, derived from the 5'-defunctionalized uridine core moiety of muraymycins and the peptide chain of sansanmycin B, as a new scaffold for the development of antimicrobial agents. The reported muraymycin-sansanmycin hybrid scaffold showed nanomolar activity against the bacterial target enzyme MraY, but displayed no significant antibacterial activity against S. aureus, E. coli, and P. aeruginosa.

Elucidating the Structural Requirement of Uridylpeptide Antibiotics for Antibacterial Activity.

The synthesis and biological evaluation of analogues of uridylpeptide antibiotics were described, and the molecular interaction between the 3'-hydroxy analogue of mureidomycin A (3'-hydroxymureidomycin A) and its target enzyme, phospho-MurNAc-pentapeptide transferase (MraY), was analyzed in detail. The structure-activity relationship (SAR) involving MraY inhibition suggests that the side chain at the urea-dipeptide moiety does not affect the MraY inhibition. However, the anti-Pseudomonas aeruginosa activity is in great contrast and the urea-dipeptide motif is a key contributor. It is also suggested that the nucleoside peptide permease NppA1A2BCD is responsible for the transport of 3'-hydroxymureidomycin A into the cytoplasm. A systematic SAR analysis of the urea-dipeptide moiety of 3'-hydroxymureidomycin A was further conducted and the antibacterial activity was determined. This study provides a guide for the rational design of analogues based on uridylpeptide antibiotics.

Simplified Novel Muraymycin Analogues; using a Serine Template Strategy for Linking Key Pharmacophores.

The present status of antibiotic research requires the urgent invention of novel agents that act on multidrug-resistant bacteria. The World Health Organization has classified antibiotic-resistant bacteria into critical, high and medium priority according to the urgency of need for new antibiotics. Naturally occurring uridine-derived "nucleoside antibiotics" have shown promising activity against numerous priority resistant organisms by inhibiting the transmembrane protein MraY (translocase I), which is yet to be explored in a clinical context. The catalytic activity of MraY is an essential process for bacterial cell viability and growth including that of priority organisms. Muraymycins are one subclass of naturally occurring MraY inhibitors. Despite having potent antibiotic properties, the structural complexity of muraymycins advocates for simplified analogues as potential lead structures. Herein, we report a systematic structure-activity relationship (SAR) study of serine template-linked, simplified muraymycin-type analogues. This preliminary SAR lead study of serine template analogues successfully revealed that the complex structure of naturally occurring muraymycins could be easily simplified to afford bioactive scaffolds against resistant priority organisms. This study will pave the way for the development of novel antibacterial lead compounds based on a simplified serine template.

Structures of Bacterial MraY and Human GPT Provide Insights into Rational Antibiotic Design.

The widespread emergence of antibiotic resistance in pathogens necessitates the development of antibacterial agents inhibiting underexplored targets in bacterial metabolism. One such target is phospho-MurNAc-pentapeptide translocase (MraY), an essential integral membrane enzyme that catalyzes the first committed step of peptidoglycan biosynthesis. MraY has long been considered a promising candidate for antibiotic development in part because it is the target of five classes of naturally occurring nucleoside inhibitors with potent in vivo and in vitro antibacterial activity. Although these inhibitors each have a nucleoside moiety, they vary dramatically in their core structures, and they have different activity properties. Until recently, the structural basis of MraY inhibition was poorly understood. Several recent structures of MraY and its human paralog, GlcNAc-1-P-transferase, have provided insights into MraY inhibition that are consistent with known inhibitor activity data and can inform rational drug design for this important antibiotic target.

Synthesis and biological evaluation of a MraY selective analogue of tunicamycins.

Tunicamycins, which are nucleoside natural products, inhibit both bacterial phospho-N-acetylmuraminic acid (MurNAc)-pentapeptide translocase (MraY) and human UDP-N-acetylglucosamine (GlcNAc): polyprenol phosphate translocase (GPT). The improved synthesis and detailed biological evaluation of an MraY-selective inhibitor, 2, where the GlcNAc moiety was modified to a MurNAc amide, has been described.

Muraymycin Nucleoside Antibiotics: Structure-Activity Relationship for Variations in the Nucleoside Unit.

Muraymycins are a subclass of naturally occurring nucleoside antibiotics with promising antibacterial activity. They inhibit the bacterial enzyme translocase I (MraY), a clinically yet unexploited target mediating an essential intracellular step of bacterial peptidoglycan biosynthesis. Several structurally simplified muraymycin analogues have already been synthesized for structure-activity relationship (SAR) studies. We now report on novel derivatives with unprecedented variations in the nucleoside unit. For the synthesis of these new muraymycin analogues, we employed a bipartite approach facilitating the introduction of different nucleosyl amino acid motifs. This also included thymidine- and 5-fluorouridine-derived nucleoside core structures. Using an in vitro assay for MraY activity, it was found that the introduction of substituents in the 5-position of the pyrimidine nucleobase led to a significant loss of inhibitory activity towards MraY. The loss of nucleobase aromaticity (by reduction of the uracil C5-C6 double bond) resulted in a ca. tenfold decrease in inhibitory potency. In contrast, removal of the 2'-hydroxy group furnished retained activity, thus demonstrating that modifications of the ribose moiety might be well-tolerated. Overall, these new SAR insights will guide the future design of novel muraymycin analogues for their potential development towards antibacterial drug candidates.

THE CONCISE GUIDE TO PHARMACOLOGY 2019/20: Enzymes.

The Concise Guide to PHARMACOLOGY 2019/20 is the fourth in this series of biennial publications. The Concise Guide provides concise overviews of the key properties of nearly 1800 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide represents approximately 400 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.14752. Enzymes are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein-coupled receptors, ion channels, nuclear hormone receptors, catalytic receptors and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2019, and supersedes data presented in the 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Liposidomycin, the first reported nucleoside antibiotic inhibitor of peptidoglycan biosynthesis translocase I: The discovery of liposidomycin and related compounds with a perspective on their application to new antibiotics.

Liposidomycin is a uridyl liponucleoside antibiotic isolated from Streptomyces griseosporeus RK-1061. It was discovered by Isono in 1985, who had previously isolated and developed a related peptidyl nucleoside antibiotic, polyoxin, a specific inhibitor of chitin synthases, as a pesticide. He subsequently isolated liposidomycin, a specific inhibitor of bacterial peptidoglycan biosynthesis from actinomycetes, using a similar approach to the discovery of polyoxin. Liposidomycin has no cytotoxicity against BALB/3T3 cells but has antimicrobial activity against Mycobacterium spp. through inhibition of MraY (MurX) [phospho-N-acetylmuramoyl-pentapeptide transferase (translocase I, EC 2.7.8.13)]. Since the discovery of liposidomycin, several liposidomycin-type antibiotics, including caprazamycin, A-90289, and muraminomycin, have been reported, and their total synthesis and/or biosynthetic cluster genes have been studied. Most advanced, a semisynthetic compound derived from caprazamycin, CPZEN-45, is being developed as an antituberculosis agent. Translocase I is an interesting and tractable molecular target for new antituberculosis and antibiotic drug discovery against multidrug-resistant bacteria. This review is dedicated to Dr Isono on the occasion of his 88th birthday to recognize his role in the study of nucleoside antibiotics.

Synthesis and biological activity of analogs of CPZEN-45, a novel antituberculosis drug.

Analogs of CPZEN-45, which is expected to be a promising new antituberculosis drug that overcomes the shortcomings of caprazamycins, were synthesized and their biological activities were evaluated. The biological activity of analogs 1-3, which converted the anilide portion, and analogs 4 and 5, focusing on the seven-membered ring, were lower than that of CPZEN-45. These results suggest that the inhibitory activity of CPZEN-45 against TagO, an ortholog of WecA, has a strict structural limitation, and it was hoped for elucidation of the mode of action of CPZEN-45 using structural biology in the future.

Mechanism of action of nucleoside antibacterial natural product antibiotics.

This article reviews the structures and biological activities of several classes of uridine-containing nucleoside antibiotics (tunicamycins, mureidomycins/pacidamycins/sansanmycins, liposidomycins/caprazamycins, muraymycins, capuramycins) that target translocase MraY on the peptidoglycan biosynthetic pathway. In particular, recent advances in structure-function studies, and recent X-ray crystal structures of translocase MraY complexed with muraymycin D2 and tunicamycin are described. The inhibition of other phospho-nucleotide transferase enzymes related to MraY by nucleoside antibiotics and analogues is also reviewed.

Muraminomicins, new lipo-nucleoside antibiotics from Streptosporangium sp. SANK 60501-structure elucidations of muraminomicins and supply of the core component for derivatization.

We screened for bacterial phospho-N-acetylmuramyl-pentapeptide-translocase (MraY: EC 2.7.8.13) inhibitors with the aim of discovering novel antibiotics and observed inhibitory activity in the culture broth of an actinomycete, SANK 60501. The active compounds, muraminomicins A, B, C, D, E1, E2, F, G, H, and I exhibited strong inhibitory activity against MraY with IC50 values of 0.0105, 0.0068, 0.0104, 0.0099, 0.0115, 0.0109, 0.0089, 0.0134, 0.0186, and 0.0094 µg ml-1, respectively. Although muraminomicin F exhibited favorable antibacterial activity against drug-resistant Gram-positive bacteria, this activity was reduced with the addition of serum. To efficiently supply the core component for chemical modification studies, production was carried out in a controlled trial by adding myristic acid to the medium, and a purification method suitable for large-scale production was successfully developed.

Chemical logic of MraY inhibition by antibacterial nucleoside natural products.

Novel antibacterial agents are needed to address the emergence of global antibiotic resistance. MraY is a promising candidate for antibiotic development because it is the target of five classes of naturally occurring nucleoside inhibitors with potent antibacterial activity. Although these natural products share a common uridine moiety, their core structures vary substantially and they exhibit different activity profiles. An incomplete understanding of the structural and mechanistic basis of MraY inhibition has hindered the translation of these compounds to the clinic. Here we present crystal structures of MraY in complex with representative members of the liposidomycin/caprazamycin, capuramycin, and mureidomycin classes of nucleoside inhibitors. Our structures reveal cryptic druggable hot spots in the shallow inhibitor binding site of MraY that were not previously appreciated. Structural analyses of nucleoside inhibitor binding provide insights into the chemical logic of MraY inhibition, which can guide novel approaches to MraY-targeted antibiotic design.

Caprazamycins: Biosynthesis and structure activity relationship studies.

Cell wall biosynthesis represents a valid target for antibacterial action but only a limited number of chemical structure classes selectively interact with specific enzymes or protein structures like transporters of the cell envelope. The integral membrane protein MraY translocase is essential for peptidoglycan biosynthesis catalysing the transfer of the peptidoglycan precursor phospho-MurNAc-pentapeptide to the lipid carrier undecaprenyl phosphate, thereby generating the cell wall intermediate lipid I. Not present in eukaryotic cells, MraY is a member of the superfamily of yet not well-understood integral membrane enzymes which involve proteins for bacterial lipopolysaccharide and teichoic acid or eukaryotic N-linked saccharides biosynthesis. Different natural nucleoside antibiotics as inhibitors of MraY translocase have been discovered comprising a glycosylated heterocyclic pyrimidin base among other potential lipid-, peptidic- or sugar moieties. Caprazamycins are liponucleoside antibiotics isolated from Streptomyces sp. MK730-62F2. They possess activity in vitro against Gram-positive bacteria, in particular against the genus Mycobacterium including M. intracellulare, M. avium and M. tuberculosis. Structural elucidation revealed the (+)-caprazol core skeleton as a unique moiety, the caprazamycins share with other MraY inhibitors such as the liposidomycins, A-90289 and the muraminomicins. They also share structural features such as uridyl-, aminoribosyl- and fatty acyl-moieties with other MraY translocase inhibitors like FR-900493 and the muraymycins. Intensive studies on their biosynthesis during the last decade identified not only common initial biosynthetic steps, but also revealed possible branching points towards individual biosynthesis of the respective compound. Structural diversity of caprazamycins was generated by feeding experiments, genetic engineering of the biosynthetic gene clusters and chemical synthesis for structure activity relationship studies with its target, MraY translocase.

Caprazamycins: Promising lead structures acting on a novel antibacterial target MraY.

The present status of antibiotic resistant requires an urgent invention of novel agents that act on clinically unexplored antibacterial targets. The enzyme MraY (phospho-MurNAc-pentapeptide translocase), essential for bacterial cell wall synthesis, fulfils this criterion as it has not been explored as a target in a clinical context. Specifically, the enzyme is involved in the lipid-linked cycle of peptidoglycan biosynthesis and is reportedly targeted by naturally-occurring nucleoside antibiotics. The antimicrobial 'caprazamycin' class of nucleoside antibiotics targets Mycobacterium tuberculosis and clinically relevant Gram-negative bacteria such as Pseudomonas aeruginosa besides various drug resistant strains and is therefore an eligible starting point for the development of novel agents. In this review, we aim to summarise the structure-activity relationships of the natural, semi-synthetic as well as synthetic analogues of nucleoside antibiotic caprazamycins. This review highlights caprazamycins as promising lead structures for development of potent and selective antimicrobial agents that target MraY, the bacterial enzyme involved in the first membrane-dependent step in bacterial peptidoglycan assembly.

A patent review of bisphosphonates in treating bone disease.

INTRODUCTION: Bisphosphonates (BPs) are widely used to manage a variety of bone disorders, including osteoporosis, metastatic bone disease and myeloma bone disease. The nitrogen-containing BPs (NBPs) target osteoclast activity by disrupting protein prenylation via inhibition of farnesyl diphosphate synthase (FDPS). AREAS COVERED: This review summarizes the recent advances in BPs with a focus on the latest patents (2015-2018). Patents involving novel BPs, new modes of BP delivery, as well as use of BPs to deliver other drugs to bone are discussed. A review of phosphonate-based drugs targeting geranylgeranyl diphosphate synthase (GGDPS) or geranylgeranyl transferase II (GGTase II) as alternative strategies to disrupt protein geranylgeranylation is provided. EXPERT OPINION: While the NBPs remain the mainstay of treatment for most bone disorders, further understanding of their pharmacological properties could lead to further refinement of their chemical structures and optimization of efficacy and safety profiles. In addition, the development of NBP analogs or drug delivery mechanisms that allow for nonbone tissue exposure could allow for the use of these drugs as direct anticancer agents. The development of GGDPS and GGTase II inhibitors represents alternative heterocycle phosphonate-based strategies to disrupt protein geranylgeranylation and may have potential as anticancer agents and/or as bone-targeted therapies.

Structural requirement of tunicamycin V for MraY inhibition.

Elucidating a structure-activity relationship study by evaluating a series of truncated analogues is a simple but important and effective tactic in medicinal chemistry based on natural products with a large and complex chemical structure. In this study, a series of truncated analogues of tunicamycin V were designed and synthesized and their MraY inhibitory activity was investigated in order to gain insight into the effect of these moieties on MraY inhibition.

Enamide Prodrugs of Acetyl Phosphonate Deoxy-d-xylulose-5-phosphate Synthase Inhibitors as Potent Antibacterial Agents.

To fight the growing threat of antibiotic resistance, new antibiotics are required that target essential bacterial processes other than protein, DNA/RNA, and cell wall synthesis, which constitute the majority of currently used antibiotics. 1-Deoxy-d-xylulose-5-phosphate (DXP) synthase is a vital enzyme in bacterial central metabolism, feeding into the de novo synthesis of thiamine diphosphate, pyridoxal phosphate, and essential isoprenoid precursors isopentenyl diphosphate and dimethylallyl diphosphate. While potent and selective inhibitors of DXP synthase in vitro activity have been discovered, their antibacterial activity is modest. To improve the antibacterial activity of selective alkyl acetylphosphonate (alkylAP) inhibitors of DXP synthase, we synthesized peptidic enamide prodrugs of alkylAPs inspired by the natural product dehydrophos, a prodrug of methyl acetylphosphonate. This prodrug strategy achieves dramatic increases in activity against Gram-negative pathogens for two alkylAPs, butyl acetylphosphonate and homopropargyl acetylphosphonate, decreasing minimum inhibitory concentrations against Escherichia coli by 33- and nearly 2000-fold, respectively. Antimicrobial studies and LC-MS/MS analysis of alkylAP-treated E. coli establish that the increased potency of prodrugs is due to increased accumulation of alkylAP inhibitors of DXP synthase via transport of the prodrug through the OppA peptide permease and subsequent amide hydrolysis. This work demonstrates the promise of targeting DXP synthase for the development of novel antibacterial agents.