RESUMEN
Aging is a complex progression of changes best characterized as the chronic dysregulation of cellular processes leading to deteriorated tissue and organ function. Although aging cannot currently be prevented, its impact on life- and healthspan in the elderly can potentially be minimized by interventions that aim to return these cellular processes to optimal function. Recent studies have demonstrated that partial reprogramming using the Yamanaka factors (or a subset; OCT4, SOX2, and KLF4; OSK) can reverse age-related changes in vitro and in vivo. However, it is still unknown whether the Yamanaka factors (or a subset) are capable of extending the lifespan of aged wild-type (WT) mice. In this study, we show that systemically delivered adeno-associated viruses, encoding an inducible OSK system, in 124-week-old male mice extend the median remaining lifespan by 109% over WT controls and enhance several health parameters. Importantly, we observed a significant improvement in frailty scores indicating that we were able to improve the healthspan along with increasing the lifespan. Furthermore, in human keratinocytes expressing exogenous OSK, we observed significant epigenetic markers of age reversal, suggesting a potential reregulation of genetic networks to a younger potentially healthier state. Together, these results may have important implications for the development of partial reprogramming interventions to reverse age-associated diseases in the elderly.
Asunto(s)
Envejecimiento , Longevidad , Anciano , Masculino , Humanos , Animales , Ratones , Longevidad/genética , Envejecimiento/genética , Terapia Genética , Queratinocitos , Reprogramación CelularRESUMEN
Herein, we describe the discovery and optimization of a novel series that inhibits bacterial DNA gyrase and topoisomerase IV via binding to, and stabilization of, DNA cleavage complexes. Optimization of this series led to the identification of compound 25, which has potent activity against Gram-positive bacteria, a favorable in vitro safety profile, and excellent in vivo pharmacokinetic properties. Compound 25 was found to be efficacious against fluoroquinolone-sensitive Staphylococcus aureus infection in a mouse thigh model at lower doses than moxifloxacin. An X-ray crystal structure of the ternary complex formed by topoisomerase IV from Klebsiella pneumoniae, compound 25, and cleaved DNA indicates that this compound does not engage in a water-metal ion bridge interaction and forms no direct contacts with residues in the quinolone resistance determining region (QRDR). This suggests a structural basis for the reduced impact of QRDR mutations on antibacterial activity of 25 compared to fluoroquinolones.
Asunto(s)
Antibacterianos/farmacología , Girasa de ADN/metabolismo , Topoisomerasa de ADN IV/antagonistas & inhibidores , Diseño de Fármacos , Fluoroquinolonas/farmacología , Staphylococcus aureus/efectos de los fármacos , Inhibidores de Topoisomerasa II/farmacología , Animales , Antibacterianos/química , Farmacorresistencia Bacteriana/efectos de los fármacos , Ratones , Inhibidores de Topoisomerasa II/químicaRESUMEN
Since their discovery over 5 decades ago, quinolone antibiotics have found enormous success as broad spectrum agents that exert their activity through dual inhibition of bacterial DNA gyrase and topoisomerase IV. Increasing rates of resistance, driven largely by target-based mutations in the GyrA/ParC quinolone resistance determining region, have eroded the utility and threaten the future use of this vital class of antibiotics. Herein we describe the discovery and optimization of a series of 4-(aminomethyl)quinolin-2(1H)-ones, exemplified by 34, that inhibit bacterial DNA gyrase and topoisomerase IV and display potent activity against ciprofloxacin-resistant Gram-negative pathogens. X-ray crystallography reveals that 34 occupies the classical quinolone binding site in the topoisomerase IV-DNA cleavage complex but does not form significant contacts with residues in the quinolone resistance determining region.
Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana/efectos de los fármacos , Fluoroquinolonas/farmacología , Bacterias Gramnegativas/efectos de los fármacos , Inhibidores de Topoisomerasa II/farmacología , Antibacterianos/síntesis química , Antibacterianos/metabolismo , Antibacterianos/toxicidad , Sitios de Unión , Línea Celular Tumoral , Girasa de ADN/metabolismo , Topoisomerasa de ADN IV/antagonistas & inhibidores , Topoisomerasa de ADN IV/química , Fluoroquinolonas/síntesis química , Fluoroquinolonas/metabolismo , Fluoroquinolonas/toxicidad , Bacterias Gramnegativas/enzimología , Humanos , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Relación Estructura-Actividad , Inhibidores de Topoisomerasa II/síntesis química , Inhibidores de Topoisomerasa II/metabolismo , Inhibidores de Topoisomerasa II/toxicidadRESUMEN
Resistance in Gram-negative bacteria to ß-lactam drugs is mediated primarily by the expression of ß-lactamases, and co-dosing of ß-lactams with a ß-lactamase inhibitor (BLI) is a clinically proven strategy to address resistance. New ß-lactamases that are not impacted by existing BLIs are spreading and creating the need for development of novel broader spectrum BLIs. IID572 is a novel broad spectrum BLI of the diazabicyclooctane (DBO) class that is able to restore the antibacterial activity of piperacillin against piperacillin/tazobactam-resistant clinical isolates. IID572 is differentiated from other DBOs by its broad inhibition of ß-lactamases and the lack of intrinsic antibacterial activity.
Asunto(s)
Compuestos de Azabiciclo/síntesis química , Bacterias Gramnegativas/efectos de los fármacos , Inhibidores de beta-Lactamasas/síntesis química , Antibacterianos/síntesis química , Antibacterianos/química , Antibacterianos/farmacología , Compuestos de Azabiciclo/química , Compuestos de Azabiciclo/farmacología , Farmacorresistencia Microbiana/efectos de los fármacos , Estabilidad de Medicamentos , Bacterias Gramnegativas/enzimología , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Inhibidores de beta-Lactamasas/química , Inhibidores de beta-Lactamasas/farmacologíaRESUMEN
Lipopolysacharride (LPS) forms the outer leaflet of the outer membrane in Gram-negative bacteria and contributes to the permeability barrier and immune response. In this study, we established a method for monitoring the LPS biosynthetic intermediates of the Raetz pathway (lpxA-lpxK) in Escherichia coli. Metabolites from compound-treated cells and genetically-perturbed cells were extracted from whole cells and concentrated by mixed-mode weak anion exchange (WAX) solid-phase extraction (SPE) prior to analysis by normal phase (NP)LC-MS/MS. Data was normalized to cell density and an internal standard prior to comparison against untreated cells in order to determine fold accumulation and depletion for affected metabolites. Using this LC-MS/MS method, we were able to reliably monitor changes in levels of the LPS intermediates in response to compound-treatment and genetic modification. In addition, we found that deletion of periplasmic CDP-diacylglycerol pyrophosphatase dramatically increased levels of the UDP-containing LPS intermediates, suggesting the enzymatic breakdown during sample preparation. This assay allows for probing a key essential pathway in Gram-negative bacteria in an effort to discover antibacterial agents that inhibit enzymes in the LPS biosynthetic pathway.
Asunto(s)
Escherichia coli/metabolismo , Lipopolisacáridos/biosíntesis , Periplasma/metabolismo , Aciltransferasas/genética , Escherichia coli/genética , Lipopolisacáridos/genética , Periplasma/genéticaRESUMEN
The monobactam scaffold is attractive for the development of new agents to treat infections caused by drug-resistant Gram-negative bacteria because it is stable to metallo-ß-lactamases (MBLs). However, the clinically used monobactam aztreonam lacks stability to serine ß-lactamases (SBLs) that are often coexpressed with MBLs. LYS228 is stable to MBLs and most SBLs. LYS228 bound purified Escherichia coli penicillin binding protein 3 (PBP3) similarly to aztreonam (derived acylation rate/equilibrium dissociation constant [k2/Kd ] of 367,504 s-1 M-1 and 409,229 s-1 M-1, respectively) according to stopped-flow fluorimetry. A gel-based assay showed that LYS228 bound mainly to E. coli PBP3, with weaker binding to PBP1a and PBP1b. Exposing E. coli cells to LYS228 caused filamentation consistent with impaired cell division. No single-step mutants were selected from 12 Enterobacteriaceae strains expressing different classes of ß-lactamases at 8× the MIC of LYS228 (frequency, <2.5 × 10-9). At 4× the MIC, mutants were selected from 2 of 12 strains at frequencies of 1.8 × 10-7 and 4.2 × 10-9 LYS228 MICs were ≤2 µg/ml against all mutants. These frequencies compared favorably to those for meropenem and tigecycline. Mutations decreasing LYS228 susceptibility occurred in ramR and cpxA (Klebsiella pneumoniae) and baeS (E. coli and K. pneumoniae). Susceptibility of E. coli ATCC 25922 to LYS228 decreased 256-fold (MIC, 0.125 to 32 µg/ml) after 20 serial passages. Mutants accumulated mutations in ftsI (encoding the target, PBP3), baeR, acrD, envZ, sucB, and rfaI These results support the continued development of LYS228, which is currently undergoing phase II clinical trials for complicated intraabdominal infection and complicated urinary tract infection (registered at ClinicalTrials.gov under identifiers NCT03377426 and NCT03354754).
Asunto(s)
Antibacterianos/farmacología , Escherichia coli/enzimología , Escherichia coli/genética , Klebsiella pneumoniae/enzimología , Klebsiella pneumoniae/genética , Monobactamas/farmacología , Aztreonam/farmacología , Enterobacteriaceae/efectos de los fármacos , Enterobacteriaceae/enzimología , Enterobacteriaceae/genética , Escherichia coli/efectos de los fármacos , Klebsiella pneumoniae/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Mutación/genética , beta-Lactamasas/genéticaRESUMEN
Metallo-ß-lactamases (MBLs), such as New Delhi metallo-ß-lactamase (NDM-1) have spread world-wide and present a serious threat. Expression of MBLs confers resistance in Gram-negative bacteria to all classes of ß-lactam antibiotics, with the exception of monobactams, which are intrinsically stable to MBLs. However, existing first generation monobactam drugs like aztreonam have limited clinical utility against MBL-expressing strains because they are impacted by serine ß-lactamases (SBLs), which are often co-expressed in clinical isolates. Here, we optimized novel monobactams for stability against SBLs, which led to the identification of LYS228 (compound 31). LYS228 is potent in the presence of all classes of ß-lactamases and shows potent activity against carbapenem-resistant isolates of Enterobacteriaceae (CRE).
Asunto(s)
Antibacterianos/farmacología , Proteínas Bacterianas/metabolismo , Enterobacteriaceae Resistentes a los Carbapenémicos/efectos de los fármacos , Monobactamas/farmacología , Resistencia betalactámica/efectos de los fármacos , beta-Lactamasas/metabolismo , Animales , Antibacterianos/efectos adversos , Antibacterianos/química , Antibacterianos/metabolismo , Aztreonam/farmacología , Células CHO , Cricetulus , Estabilidad de Medicamentos , Escherichia coli/efectos de los fármacos , Femenino , Humanos , Meropenem , Ratones , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Monobactamas/efectos adversos , Monobactamas/química , Monobactamas/metabolismo , Pseudomonas aeruginosa/efectos de los fármacos , Receptores de GABA-A/metabolismo , Convulsiones/inducido químicamente , Relación Estructura-Actividad , Tienamicinas/farmacologíaRESUMEN
Acinetobacter baumannii ATCC 19606 can grow without lipid A, the major component of lipooligosaccharide. However, we previously reported that depletion of LpxH (the fourth enzyme in the lipid A biosynthetic pathway) prevented growth of this strain due to toxic accumulation of lipid A pathway intermediates. Here, we explored whether a similar phenomenon occurred with depletion of LpxK, a kinase that phosphorylates disaccharide 1-monophosphate (DSMP) at the 4' position to yield lipid IVA. An A. baumannii ATCC 19606 derivative with LpxK expression under the control of an isopropyl ß-d-1-thiogalactopyranoside (IPTG)-regulated expression system failed to grow without induction, indicating that LpxK is essential for growth. Light and electron microscopy of LpxK-depleted cells revealed morphological changes relating to the cell envelope, consistent with toxic accumulation of lipid A pathway intermediates disrupting cell membranes. Using liquid chromatography-mass spectrometry (LCMS), cellular accumulation of the detergent-like pathway intermediates DSMP and lipid X was shown. Toxic accumulation was further supported by restoration of growth upon chemical inhibition of LpxC (upstream of LpxK and the first committed step of lipid A biosynthesis) using CHIR-090. Inhibitors of fatty acid synthesis also abrogated the requirement for LpxK expression. Growth rescue with these inhibitors was possible on Mueller-Hinton agar but not on MacConkey agar. The latter contains outer membrane-impermeable bile salts, suggesting that despite growth restoration, the cell membrane permeability barrier was not restored. Therefore, LpxK is essential for growth of A. baumannii, since loss of LpxK causes accumulation of detergent-like pathway intermediates that inhibit cell growth. IMPORTANCEAcinetobacter baumannii is a Gram-negative pathogen for which new therapies are needed. The lipid A biosynthetic pathway has several potential enzyme targets for the development of anti-Gram-negative agents (e.g., LpxC). However, A. baumannii ATCC 19606 can grow in the absence of LpxC and, correspondingly, of lipid A. In contrast, we show that cellular depletion of LpxK, a kinase occurring later in the pathway, inhibits growth. Growth inhibition results from toxic accumulation of lipid A pathway intermediates, since chemical inhibition of LpxC or fatty acid biosynthesis rescues cell growth upon loss of LpxK. Overall, this suggests that targets such as LpxK can be essential for growth even in those Gram-negative bacteria that do not require lipid A biosynthesis per se. This strain provides an elegant tool to derive a better understanding of the steps in a pathway that is the focus of intense interest for the development of novel antibacterials.
RESUMEN
Gram-negative bacteria possess a characteristic outer membrane, of which the lipid A constituent elicits a strong host immune response through the Toll-like receptor 4 complex, and acts as a component of the permeability barrier to prevent uptake of bactericidal compounds. Lipid A species comprise the bulk of the outer leaflet of the outer membrane and are produced through a multistep biosynthetic pathway conserved in most Gram-negative bacteria. The final steps in this pathway involve the secondary acylation of lipid A precursors. These are catalyzed by members of a superfamily of enzymes known as lysophospholipid acyltransferases (LPLATs), which are present in all domains of life and play important roles in diverse biological processes. To date, characterization of this clinically important class of enzymes has been limited by a lack of structural information and the availability of only low-throughput biochemical assays. In this work, we present the structure of the bacterial LPLAT protein LpxM, and we describe a high-throughput, label-free mass spectrometric assay to characterize acyltransferase enzymatic activity. Using our structure and assay, we identify an LPLAT thioesterase activity, and we provide experimental evidence to support an ordered-binding and "reset" mechanistic model for LpxM function. This work enables the interrogation of other bacterial acyltransferases' structure-mechanism relationships, and the assay described herein provides a foundation for quantitatively characterizing the enzymology of any number of clinically relevant LPLAT proteins.
Asunto(s)
Aciltransferasas/química , Aciltransferasas/metabolismo , Lípido A/química , Lípido A/metabolismo , Secuencia de Aminoácidos , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Sitios de Unión , Secuencia de Consenso , Activación Enzimática , Bacterias Gramnegativas , Interacciones Hidrofóbicas e Hidrofílicas , Cinética , Modelos Moleculares , Posición Específica de Matrices de Puntuación , Unión Proteica , Conformación Proteica , Relación Estructura-Actividad , Tioléster Hidrolasas/química , Tioléster Hidrolasas/metabolismoRESUMEN
The lipid A moiety of lipopolysaccharide (LPS) is the main constituent of the outer leaflet of the Gram-negative bacterial outer membrane (OM) and is essential in many Gram-negative pathogens. An exception is Acinetobacter baumannii ATCC 19606, where mutants lacking enzymes occurring early in lipid A biosynthesis (LpxA, LpxC or LpxD), and correspondingly lacking LPS, can grow. In contrast, we show here that LpxH, an enzyme that occurs downstream of LpxD in the lipid A biosynthetic pathway, is essential for growth in this strain. Multiple attempts to disrupt lpxH on the genome were unsuccessful, and when LpxH expression was controlled by an isopropyl ß-d-1-thiogalactopyranoside (IPTG) inducible promoter, cell growth under typical laboratory conditions required IPTG induction. Mass spectrometry analysis of cells shifted from LpxH-induced to uninduced (and whose growth was correspondingly slowing as LpxH was depleted) showed a large cellular accumulation of UDP-2,3-diacyl-GlcN (substrate of LpxH), a C14:0(3-OH) acyl variant of the LpxD substrate (UDP-3-O-[(R)-3-OH-C14]-GlcN), and disaccharide 1-monophosphate (DSMP). Furthermore, the viable cell counts of the LpxH depleted cultures dropped modestly, and electron microscopy revealed clear defects at the cell (inner) membrane, suggesting lipid A intermediate accumulation was toxic. Consistent with this, blocking the synthesis of these intermediates by inhibition of the upstream LpxC enzyme using CHIR-090 abrogated the requirement for IPTG induction of LpxH. Taken together, these data indicate that LpxH is essential for growth in A. baumannii ATCC19606, because, unlike earlier pathway steps like LpxA or LpxC, blockage of LpxH causes accumulation of detergent-like pathway intermediates that prevents cell growth.
Asunto(s)
Acinetobacter baumannii/crecimiento & desarrollo , Acinetobacter baumannii/metabolismo , Proteínas Bacterianas/metabolismo , Lípido A/metabolismo , Acinetobacter baumannii/genética , Regulación Bacteriana de la Expresión Génica , Lípido A/toxicidadRESUMEN
Successful isolation of well-folded and active protein often first requires the creation of many constructs. These are needed to assess the effects of truncations, insertions, mutations, and the presence and position of different affinity tags. Determining which constructs yield the highest expression and solubility requires the investigator to express and partially purify each construct, and, in the case of low-expressing proteins, to follow the protein using time-consuming Western blots. Even then, many proteins form soluble aggregates, which may only be apparent after more extensive purification via size exclusion chromatography. In this work, we have utilized a covalent bond-forming tag/domain pair, known as SpyTag/SpyCatcher, to rapidly and specifically attach a fluorescent label to proteins of interest in cellular lysates. Once labeled, tagged proteins can easily be followed via SDS-PAGE and fluorescence size exclusion chromatography (F-SEC) to assess expression levels, solubility, and monodispersity without the need for purification. These techniques enable rapid and facile analysis of proteins, which may greatly facilitate optimization of protein expression constructs.
Asunto(s)
Adhesinas Bacterianas , Proteínas Portadoras , Proteínas de Escherichia coli , Expresión Génica , Proteínas Periplasmáticas , Adhesinas Bacterianas/biosíntesis , Adhesinas Bacterianas/química , Adhesinas Bacterianas/genética , Adhesinas Bacterianas/aislamiento & purificación , Proteínas Portadoras/biosíntesis , Proteínas Portadoras/química , Proteínas Portadoras/genética , Proteínas Portadoras/aislamiento & purificación , Escherichia coli/química , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Escherichia coli/biosíntesis , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/aislamiento & purificación , Proteínas Periplasmáticas/biosíntesis , Proteínas Periplasmáticas/química , Proteínas Periplasmáticas/genética , Proteínas Periplasmáticas/aislamiento & purificación , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/aislamiento & purificación , SolubilidadRESUMEN
Enzymes in lipid metabolism acquire and deliver hydrophobic substrates and products from within lipid bilayers. The structure at 2.55 Å of one isozyme of a constitutive enzyme in lipid A biosynthesis, LpxI from Caulobacter crescentus, has a novel fold. Two domains close around a completely sequestered substrate, UDP-2,3-diacylglucosamine, and open to release products either to the neighboring enzyme in a putative multienzyme complex or to the bilayer. Mutation analysis identifies Asp225 as key to Mg(2+)-catalyzed diphosphate hydrolysis. These structures provide snapshots of the enzymatic synthesis of a critical lipid A precursor.
Asunto(s)
Caulobacter crescentus/enzimología , Lípido A/biosíntesis , Modelos Moleculares , Conformación Proteica , Pirofosfatasas/química , Secuencia de Aminoácidos , Cristalización , Análisis Mutacional de ADN , Glucolípidos/metabolismo , Isoenzimas/química , Espectrometría de Masas , Datos de Secuencia Molecular , Estructura Molecular , Pliegue de Proteína , Pirofosfatasas/genética , UltracentrifugaciónRESUMEN
The outer leaflet of the outer membranes of Gram-negative bacteria is composed primarily of lipid A, the hydrophobic anchor of lipopolysaccharide. Like Escherichia coli, most Gram-negative bacteria encode one copy of each of the nine genes required for lipid A biosynthesis. An important exception exists in the case of the fourth enzyme, LpxH, a peripheral membrane protein that hydrolyzes UDP-2,3-diacylglucosamine to form 2,3-diacylglucosamine 1-phosphate and UMP by catalyzing the attack of water at the alpha-P atom. Many Gram-negative organisms, including all alpha-proteobacteria and diverse environmental isolates, lack LpxH. Here, we report a distinct UDP-2,3-diacylglucosamine pyrophosphatase, designated LpxI, which has no sequence similarity to LpxH but generates the same products by a different route. LpxI was identified because its structural gene is located between lpxA and lpxB in Caulobacter crescentus. The lpxI gene rescues the conditional lethality of lpxH-deficient E. coli. Lysates of E. coli in which C. crescentus LpxI (CcLpxI) is overexpressed display high levels of UDP-2,3-diacylglucosamine pyrophosphatase activity. CcLpxI was purified to >90% homogeneity. CcLpxI is stimulated by divalent cations and is inhibited by EDTA. Unlike E. coli LpxH, CcLpxI is not inhibited by an increase in the concentration of detergent, and its pH dependency is different. When the CcLpxI reaction is conducted in the presence of H(2)(18)O, the (18)O is incorporated exclusively into the 2,3-diacylglucosamine 1-phosphate product, as judged by mass spectrometry, demonstrating that CcLpxI catalyzes the attack of water on the beta-P atom of UDP-2,3-diacylglucosamine.
Asunto(s)
Caulobacter crescentus/metabolismo , Lípido A/biosíntesis , Pirofosfatasas/metabolismo , Caulobacter crescentus/enzimología , Detergentes/farmacología , Concentración de Iones de Hidrógeno , Hidrólisis , Redes y Vías Metabólicas , Agua/químicaRESUMEN
Escherichia coli LpxB, an inverting glycosyl transferase of the GT-B superfamily and a member of CAZy database family 19, catalyzes the fifth step of lipid A biosynthesis: UDP-2,3-diacylglucosamine + 2,3-diacylglucosamine 1-phosphate --> 2',3'-diacylglucosamine-(beta,1'-6)-2,3-diacylglucosamine 1-phosphate + UDP. LpxB is a target for the development of new antibiotics, but no member of family 19, which consists entirely of LpxB orthologues, has been characterized mechanistically or structurally. Here, we have purified E. coli and Haemophilus influenzae LpxB to near homogeneity on a 10-100 mg scale using protease-cleavable His(10)-tagged constructs. E. coli LpxB activity is dependent upon the bulk surface concentration of its substrates in a mixed micelle assay system, suggesting that catalysis occurs at the membrane interface. E. coli LpxB (M(r) approximately 43 kDa) sediments with membranes at low salt concentrations but is largely solubilized with buffers of high ionic strength. It purifies with 1.6-3.5 mol of phospholipid/mol of LpxB polypeptide. Transmission electron microscopy reveals the accumulation of aberrant intracellular membranes when LpxB is overexpressed. Mutagenesis of LpxB identified two conserved residues, D89A and R201A, for which no residual catalytic activity was detected. Our results provide a rational starting point for structural studies.
Asunto(s)
Proteínas Bacterianas/metabolismo , Escherichia coli/enzimología , Haemophilus influenzae/enzimología , Proteínas de la Membrana/metabolismo , N-Acetilglucosaminiltransferasas/metabolismo , Catálisis , Cromatografía en Gel , Electroforesis en Gel de Poliacrilamida , Espectrometría de Masas , Microscopía Electrónica de Transmisión , N-Acetilglucosaminiltransferasas/química , N-Acetilglucosaminiltransferasas/aislamiento & purificación , Concentración Osmolar , Péptido Hidrolasas/metabolismo , Sales (Química)/químicaRESUMEN
Hsp90 chaperones contain an N-terminal ATP binding site that has been effectively targeted by competitive inhibitors. Despite the myriad of inhibitors, none to date have been designed to bind specifically to just one of the four mammalian Hsp90 paralogs, which are cytoplasmic Hsp90alpha and beta, endoplasmic reticulum GRP94, and mitochondrial Trap-1. Given that each of the Hsp90 paralogs is responsible for chaperoning a distinct set of client proteins, specific targeting of one Hsp90 paralog may result in higher efficacy and therapeutic control. Specific inhibitors may also help elucidate the biochemical roles of each Hsp90 paralog. Here, we present side-by-side comparisons of the structures of yeast Hsp90 and mammalian GRP94, bound to the pan-Hsp90 inhibitors geldanamycin (Gdm) and radamide. These structures reveal paralog-specific differences in the Hsp90 and GRP94 conformations in response to Gdm binding. We also report significant variation in the pose and disparate binding affinities for the Gdm-radicicol chimera radamide when bound to the two paralogs, which may be exploited in the design of paralog-specific inhibitors.
Asunto(s)
Diseño de Fármacos , Proteínas HSP70 de Choque Térmico , Proteínas HSP90 de Choque Térmico , Proteínas de la Membrana , Acetanilidas/química , Acetanilidas/metabolismo , Animales , Benzoatos/química , Benzoatos/metabolismo , Benzoquinonas/química , Benzoquinonas/metabolismo , Sitios de Unión , Cristalización , Perros , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/metabolismo , Proteínas HSP70 de Choque Térmico/química , Proteínas HSP70 de Choque Térmico/metabolismo , Proteínas HSP90 de Choque Térmico/química , Proteínas HSP90 de Choque Térmico/metabolismo , Humanos , Lactamas Macrocíclicas/química , Lactamas Macrocíclicas/metabolismo , Ligandos , Macrólidos/química , Macrólidos/metabolismo , Proteínas de la Membrana/química , Proteínas de la Membrana/metabolismo , Modelos Moleculares , Datos de Secuencia Molecular , Estructura Molecular , Estructura Terciaria de Proteína , Electricidad Estática , Difracción de Rayos XRESUMEN
17-beta-Hydroxysteroid dehydrogenase type 1 (17betaHSD1), also called estradiol dehydrogenase, catalyzes the NADPH-dependent reduction of the weak estrogen, estrone, into the more potent estrogen, 17-beta-estradiol. 17betaHSD1 is an attractive drug target in hormone-sensitive breast cancer. Past efforts to develop selective inhibitors of 17betaHSD1 have focused on design of substrate analogs. It is challenging to develop steroid analogs that are devoid of any undesired biological activity. 17betaHSD1 is a member of the short-chain dehydrogenase/reductase (SDR) superfamily that includes many hydroxysteroid dehydrogenases. Members of the SDR family bind NAD(P)(H) in a motif that is a modified Rossmann fold. We demonstrated previously that the Rossmann folds of classical dehydrogenases can be selectively inhibited by derivatives and analogs of the natural product gossypol. In this study, we have addressed the question whether the modified Rossmann fold in 17betaHSD1 is a target for identification of lead compounds for structure-based drug design. 17betaHSD1 was purified from human placenta. 17betaHSD1 is inhibited by derivatives of gossypol with dissociation constants as low as 2 microM. Inhibition is competitive with the binding of cofactor. Molecular modeling studies using the published coordinates of human 17betaHSD1 suggest that these inhibitors occupy the modified Rossmann fold at the nicotinamide end of the dinucleotide-binding site, extending towards the substrate site. A computational approach was used to design potential new inhibitors of 17betaHSD1. The results suggest not only that derivatives of gossypol represent attractive lead compounds for structure-based drug design but also suggest that appropriate incorporation of a substrate analog into the design of these Rossmann fold inhibitors may provide pan-active site inhibitors that span the cofactor and substrate site, potentially offering specificity and increased potency.