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The E.3.3 mutation was generated in a Flp/FRT EMS screen for conditional mutations that cause growth and developmental defects in a genetic background that blocks apoptosis. The mutations were conditional, based on the Dark 82 allele being present on the starting chromosome, and blocking canonical apoptosis in a homozygous state. The E.3.3 mosaic eyes exhibit defects in eye development including patches of rough eye and irregular surface structure. Whole Genome Sequencing and complementation mapping revealed E.3.3 as an allele of prod . Prod is a DNA-binding protein that binds satellite repeats and is involved in chromocenter formation during mitosis. Here we present a novel allele of prod , prod E.3.3 , that disrupts the functional region of the Prod protein resulting in disruption of typical eye structure, likely due to disruption of chromatid separation during development.
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The vestibular short-latency evoked potential (VsEP) reflects the activity of irregular vestibular afferents and their target neurons in the brain stem. Attenuation of trial-averaged VsEP waveforms is widely accepted as an indicator of vestibular dysfunction, however, more quantitative analyses of VsEP waveforms could reveal underlying neural properties of VsEP waveforms. Here, we present a time-frequency analysis of the VsEP with a wavelet transform on a single-trial basis, which allows us to examine trial-by-trial variability in the strength of VsEP waves as well as their temporal coherence across trials. Using this method, we examined changes in the VsEP following 110 dB SPL noise exposure in rats. We found detectability of head jerks based on the power of wavelet transform coefficients was significantly reduced 1 day after noise exposure but recovered nearly to pre-exposure level in 3 - 7 days and completely by 28 days after exposure. Temporal coherence of VsEP waves across trials was also significantly reduced on 1 day after exposure but recovered with a similar time course. Additionally, we found a significant reduction in the number of calretinin-positive calyces in the sacculi collected 28 days after noise exposure. Furthermore, the number of calretinin-positive calyces was significantly correlated with the degree of reduction in temporal coherence and/or signal detectability of the smallest-amplitude jerks. This new analysis of the VsEP provides more quantitative descriptions of noise-induced changes as well as new insights into potential mechanisms underlying noise-induced vestibular dysfunction. Significance Statement: Our study presents a new method of VsEP quantification using wavelet transform on a single-trial basis. It also describes a novel approach to determine the stimulus threshold of the VsEP based on signal-detection theory and Rayleigh statistics. The present analysis could also be applied to analysis of auditory brain stem response (ABR). Thus, it has the potential to provide new insights into the physiological properties that underlie peripheral vestibular and auditory dysfunction.
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BACKGROUND: Blood management strategies in total hip arthroplasty (THA) are essential in reducing intraoperative blood loss, blood transfusion and associated complications. This study investigates whether using intraoperative cell-salvage (ICS) with tranexamic acid (TXA) has additional effects on blood loss and allogeneic transfusion in primary THA. Additionally, we evaluated the financial impact of using ICS on our institution. METHODS: Using an institutional database, 1171 cases of primary unilateral THA performed between May 2015 and January 2016 were identified. Subjects were separated into those who received only TXA (n = 323) and those who received TXA and ICS (n = 848). Calculated blood loss and post-operative blood transfusions were assessed using logistic regression. Drop in hematocrit was assessed using linear regression. Multivariable models adjusted for intraoperative blood transfusions, pre-operative autologous blood donation, anticoagulation medications, sex, and body mass index. Pricing data was used to calculate the costs associated with these interventions. RESULTS: The likelihood of post-operative allogeneic blood transfusion was similar for the combined group relative to the TXA group (OR = 0.63; 95% CI: 0.26, 1.54), as was the likelihood of any post-operative blood transfusion (OR = 1.13; 95% CI: 0.63, 2.01). There was no correlative relationship between use of ICS and hematocrit drop when accounting for baseline hematocrit (R2 = 0.118). Factoring in rental, service fees, and disposable equipment, the utilization of ICS added $146 to each case, resulting in a gross expenditure of over $123,000 during the study period. CONCLUSIONS: The combination of ICS with TXA for primary unilateral THA did not improve blood loss or transfusion outcomes compared to TXA alone. As there was no observed clinical benefit to combined treatment, additional costs associated with routine usage of ICS may not be justifiable. Our institution would have reduced expenditures for blood loss management products by 85% during the study period if all patients had only received TXA.
Assuntos
Antifibrinolíticos , Artroplastia de Quadril , Ácido Tranexâmico , Perda Sanguínea Cirúrgica/prevenção & controle , Transfusão de Sangue , HumanosRESUMO
BACKGROUND/OBJECTIVES: Rates of traumatic brain injury (TBI) among older adults and treatment of this population in nursing homes are increasing. The objective of this study is to examine differences in the quality of care and outcomes of older adults with TBI in rural and urban settings by (1) comparing the rates of successful community discharge; and (2) reasons for not achieving successful discharge among patients in rural and urban environments. DESIGN: Retrospective national cohort study of skilled nursing facility (SNF) patients using Medicare inpatient claims linked with Minimum Data Set assessments. Demographic, health, and facility characteristics were compared between rural and urban settings using descriptive statistics. Logistic regression with state random effects was used to identify characteristics that predicted successful discharge. SETTING: U.S. skilled nursing facilities (n = 11,771). PARTICIPANTS: Medicare beneficiaries aged 66 and older discharged to a SNF following hospitalization for TBI between 2011 and 2015 (n = 61,021). MEASUREMENTS: Successful community discharge defined as discharge from SNF within 100 days of admission and remaining in the community for ≥30 days without dying or admission to an inpatient healthcare facility. RESULTS: Unadjusted rates of successful discharge were significantly lower for patients in rural settings compared with patients in urban settings (52.1% vs 58.5%, p < 0.01). Patients in rural settings had lower adjusted odds (odds ratio 0.84, 95% confidence interval = 0.80-0.89) of successful discharge. Reasons for not discharging successfully differed between rural and urban settings with rural patients less likely to discharge from SNF within 100 days though also less likely to be rehospitalized within 30 days of SNF discharge. CONCLUSION: Given the low overall rate of successful community discharge and worse outcomes among rural patients, further research to explore interventions to improve SNF care and discharge planning in this population is warranted.
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Lesões Encefálicas Traumáticas , Pacientes Internados/estatística & dados numéricos , Alta do Paciente/estatística & dados numéricos , Centros de Reabilitação/estatística & dados numéricos , População Rural/estatística & dados numéricos , População Urbana/estatística & dados numéricos , Idoso de 80 Anos ou mais , Lesões Encefálicas Traumáticas/epidemiologia , Lesões Encefálicas Traumáticas/reabilitação , Feminino , Humanos , Vida Independente , Revisão da Utilização de Seguros/estatística & dados numéricos , Masculino , Medicare/estatística & dados numéricos , Readmissão do Paciente/estatística & dados numéricos , Qualidade da Assistência à Saúde/normas , Estudos Retrospectivos , Instituições de Cuidados Especializados de Enfermagem/estatística & dados numéricos , Estados UnidosRESUMO
Intraoperative fracture of the proximal tibia is a rare complication of total knee arthroplasty (TKA) with few studies available reporting risk factors or prognosis. A review of our prospective joint registry was performed to determine the incidence and associated risk factors of intraoperative tibia fractures during primary TKA; 14,966 TKAs of all manufacturers were performed with 9 intraoperative tibia fractures. All fractures occurred in a single TKA design. There were 8,155 TKAs of this design performed with a fracture incidence of 0.110%. All but one fracture occurred on the medial tibial plateau, and all but one occurred during preparation of the tibia with keel punching. A control group of 75 patients (80 knees) with the same TKA design were randomly selected. Baseplates size 3 or smaller were less likely to experience an intraoperative fracture (odds ratio [OR]: 0.864, 95% confidence interval [CI]: 0.785-0.951), as were knees with a polyethylene insert thickness of 13 mm or larger (OR: 0.882, 95% CI: 0.812-0.957). Fractures were treated with a variety of different methods, but every patient had at least one screw placed and most (67%) had postoperative weight-bearing restrictions. At final follow-up, there were no cases of nonunion, component subsidence, or need for reoperation. Intraoperative tibia fractures are a rare complication of this TKA design at 0.11%. Knees with baseplates of size ≤3 and polyethylene thickness ≥13 mm were less likely to experience intraoperative fracture. These findings may be related to the depth of tibial resection, requiring the use of a thicker polyethylene insert, and a change in the keel width in implants size 4 or larger. No fracture patients required reoperation.
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Artroplastia do Joelho , Prótese do Joelho , Fraturas Periprotéticas , Fraturas da Tíbia , Artroplastia do Joelho/efeitos adversos , Humanos , Articulação do Joelho/diagnóstico por imagem , Articulação do Joelho/cirurgia , Prótese do Joelho/efeitos adversos , Fraturas Periprotéticas/diagnóstico por imagem , Fraturas Periprotéticas/etiologia , Fraturas Periprotéticas/cirurgia , Estudos Prospectivos , Estudos Retrospectivos , Tíbia/cirurgia , Fraturas da Tíbia/diagnóstico por imagem , Fraturas da Tíbia/etiologia , Fraturas da Tíbia/cirurgiaRESUMO
During cruciate retaining (CR) total knee arthroplasty (TKA), the posterior cruciate ligament (PCL) may avulse at its insertion. The incidence of PCL avulsion fracture has not been previously studied. The aim of this study is to report on the incidence and clinical significance of intraoperative PCL avulsion during primary CR TKA and to identify potential risk factors. Our institutional joint registry was retrospectively reviewed for PCL avulsion occurring during CR TKA implanted between April 2008 and April 2016. Patient demographics, preoperative range of motion (ROM), complications, and revision rate were examined. A control group of 132 patients was used for comparison to identify potential risk factors. Forty-four of 2,457 patients (1.7%) suffered a PCL avulsion fracture during primary CR TKA. No intraoperative repair was performed and no postoperative weight bearing or ROM restrictions were implemented. There was no significant difference in BMI (p = 0.258), mean preoperative ROM (p = 0.763), or femoral and tibial component sizes (p = 0.3069, p = 0.1306) between groups. Logistic regression found female gender (p = 0.0254) to be the only statistically significant risk factor for PCL avulsion. The incidence of intraoperative PCL avulsion fracture during CR TKA is low (1.7%) and does not appear to affect postoperative ROM, subjective stability, or incidence of revision. Female gender was identified as the only patient factor that increased the risk of PCL avulsion fracture.
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Artroplastia do Joelho/efeitos adversos , Complicações Intraoperatórias/epidemiologia , Traumatismos do Joelho/epidemiologia , Ligamento Cruzado Posterior/lesões , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Fêmur/cirurgia , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Ligamento Cruzado Posterior/cirurgia , Amplitude de Movimento Articular , Estudos Retrospectivos , Fatores de Risco , Tíbia/cirurgia , Suporte de CargaRESUMO
BACKGROUND: Postoperative pain after total knee arthroplasty (TKA) may impact long-term results and incidence of complications. Femoral nerve block (FNB) provides excellent pain relief after TKA, although associated risks include weakness, delayed participation in therapy, and nerve injury. Liposomal bupivacaine (LB) is a potentially longer acting local anesthetic that may reduce postoperative pain. METHODS: We performed a prospective, randomized, double-blind study of 373 TKA patients randomized to receive either an FNB (control group), or an intraoperative periarticular injection (PAI) with LB and a placebo saline FNB (experimental group). Patients were evaluated with visual analog scores for pain, range of motion, performance of straight leg raise (SLR), walking distance, and Short Form-12 up to 1 year postoperatively. RESULTS: Twelve and 24 hours postoperatively, the control group had significantly lower pain scores (mean 3.24 vs 3.87; P = .02) and higher range of motion (84.54° vs 78°; P < .001). The patients receiving LB PAI were significantly more likely to perform a straight leg raise 12 hours postoperatively (73% vs 50%; P = .0003). Patients in the LB (experimental) group scored better in the physical function component of the Short Form-12 (-23 vs -27, P = .01) 3 months postoperatively. CONCLUSION: While pain scores were slightly lower in the control group in the first 24 hours after TKA compared with LB PAI, the magnitude of the difference was small, and excellent pain relief was provided by both interventions. Use of LB PAI in TKA is a reasonable alternative to FNB, which avoids the additional weakness and other risk associated with FNB procedures.
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Anestésicos Locais/administração & dosagem , Artroplastia do Joelho/efeitos adversos , Bupivacaína/administração & dosagem , Bloqueio Nervoso , Dor Pós-Operatória/prevenção & controle , Idoso , Anestesia por Condução , Anestesia Local , Método Duplo-Cego , Feminino , Nervo Femoral , Humanos , Injeções Intra-Articulares , Cuidados Intraoperatórios , Masculino , Pessoa de Meia-Idade , Manejo da Dor/métodos , Medição da Dor , Dor Pós-Operatória/etiologia , Período Pós-Operatório , Estudos Prospectivos , Amplitude de Movimento ArticularRESUMO
BACKGROUND: There has been a recent interest in custom-made partial knee arthroplasties to provide patient-specific instrumentation and better fit of the prosthesis. While unicondylar knee arthroplasties (UKAs) have demonstrated good outcomes and durable results in many studies, there is little evidence on outcomes of these custom-made implants. METHODS: We performed a retrospective review of all custom-made UKAs performed at our institution by one surgeon from 2008 to 2015. We analyzed preoperative demographics, clinical follow-up evaluations, and radiographs and performed an analysis of risk factors including age, gender, height, weight, body mass index, and tibial insert thickness. The incidence of revision surgery, radiographic failures indicating component loosening, and symptomatic clinically failed implants was calculated at an average of 54.0 months of follow-up. RESULTS: We analyzed 115 consecutive custom-made medial UKAs from a single surgeon at our institution and found 29 (25.2%) UKAs had failed at an average of 33.1 months after surgery. Reasons for failure included aseptic femoral loosening (10), aseptic tibial loosening (8), loosening of both components (4), infection (3), progression of osteoarthritis (2), pain (1), and dislodged polyethylene insert (1). We found a significant relationship between implant failure and body mass index; no other study variables were statistically significant. CONCLUSION: We found a relatively high rate of aseptic loosening and particularly femoral component loosening in the short- to intermediate-term follow-up period. While further study of larger numbers of custom-made UKA from multiple institutions may help verify these findings, we recommend careful consideration of the use of this implant.
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Artroplastia do Joelho/efeitos adversos , Prótese do Joelho/efeitos adversos , Reoperação/estatística & dados numéricos , Adulto , Idoso , Idoso de 80 Anos ou mais , Índice de Massa Corporal , Feminino , Fêmur/patologia , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Osteoartrite/complicações , Polietileno , Falha de Prótese , Radiografia , Estudos Retrospectivos , Fatores de Risco , Fatores de Tempo , Resultado do TratamentoRESUMO
BACKGROUND: Volunteer patients (also known as patient partners (PPs)) play a vital role in undergraduate healthcare curricula. They frequently take part in objective structured clinical examinations (OSCE) and rate aspects of students' performance. However, the inclusion and weighting of PP marks varies, while attitudes and opinions regarding how (and if) they should contribute towards the pass/fail outcome are uncertain. METHODS: A prospective observational study was conducted to explore beliefs of PPs regarding inclusion of their scores in a high stakes undergraduate OSCE in a single UK medical school. All PPs delivering components of the local MBChB curriculum were asked to participate in the questionnaire study. Quantitative and qualitative data were analysed using descriptive statistics and framework analysis respectively. RESULTS: Fifty out of 160 (31% response rate) PPs completed the questionnaire; 70% had participated in a final year OSCE. Thirty (60%) felt their marks should be incorporated into a student's overall score, while 28% were uncertain. The main reasons for inclusion were recognition of the patient perspective (31%) and their ability to assess attitudes and professionalism (27%), while reasons against inclusion included lack of PP qualification/training (18%) and concerns relating to consistency (14%). The majority of PPs were uncertain what proportion of the total mark they should contribute, although many felt that 5-10% of the total score was reasonable. Most respondents (70%) felt that globally low PP scores should not result in an automatic fail and many (62%) acknowledged that prior to mark inclusion, further training was required. CONCLUSION: These data show that most respondents considered it reasonable to "formalise their expertise" by contributing marks in the overall assessment of students in a high stakes OSCE, although what proportion they believe this should represent was variable. Some expressed concerns that using marks towards progress decisions may alter PP response patterns. It would therefore seem reasonable to compare outcomes (i.e. pass/fail status) using historical data both incorporating and not incorporating PP marks to evaluate the effects of doing so. Further attention to existing PP training programmes is also required in order to provide clear instruction on how to globally rate students to ensure validity and consistency.
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Competência Clínica/normas , Educação de Graduação em Medicina/normas , Participação do Paciente/estatística & dados numéricos , Aprendizagem Baseada em Problemas/normas , Estudantes de Medicina , Idoso , Idoso de 80 Anos ou mais , Avaliação Educacional/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Faculdades de Medicina , Inquéritos e Questionários , Reino Unido , VoluntáriosRESUMO
The nuclear receptor retinoid acid receptor-related orphan receptor γt (RORγt) is a master regulator of the Th17/IL-17 pathway that plays crucial roles in the pathogenesis of autoimmunity. RORγt has recently emerged as a highly promising target for treatment of a number of autoimmune diseases. Through high-throughput screening, we previously identified several classes of inverse agonists for RORγt. Here, we report the crystal structures for the ligand-binding domain of RORγt in both apo and ligand-bound states. We show that apo RORγt adopts an active conformation capable of recruiting coactivator peptides and present a detailed analysis of the structural determinants that stabilize helix 12 (H12) of RORγt in the active state in the absence of a ligand. The structures of ligand-bound RORγt reveal that binding of the inverse agonists disrupts critical interactions that stabilize H12. This destabilizing effect is supported by ab initio calculations and experimentally by a normalized crystallographic B-factor analysis. Of note, the H12 destabilization in the active state shifts the conformational equilibrium of RORγt toward an inactive state, which underlies the molecular mechanism of action for the inverse agonists reported here. Our findings highlight that nuclear receptor structure and function are dictated by a dynamic conformational equilibrium and that subtle changes in ligand structures can shift this equilibrium in opposite directions, leading to a functional switch from agonists to inverse agonists.
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Anti-Inflamatórios não Esteroides/farmacologia , Agonismo Inverso de Drogas , Modelos Moleculares , Membro 3 do Grupo F da Subfamília 1 de Receptores Nucleares/antagonistas & inibidores , Anti-Inflamatórios não Esteroides/química , Anti-Inflamatórios não Esteroides/metabolismo , Apoproteínas/antagonistas & inibidores , Apoproteínas/química , Apoproteínas/genética , Apoproteínas/metabolismo , Sítios de Ligação , Ligação Competitiva , Células Cultivadas , Genes Reporter/efeitos dos fármacos , Células HEK293 , Humanos , Interleucina-17/antagonistas & inibidores , Interleucina-17/metabolismo , Ligantes , Conformação Molecular , Membro 3 do Grupo F da Subfamília 1 de Receptores Nucleares/química , Membro 3 do Grupo F da Subfamília 1 de Receptores Nucleares/genética , Membro 3 do Grupo F da Subfamília 1 de Receptores Nucleares/metabolismo , Fragmentos de Peptídeos/antagonistas & inibidores , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Fenilalanina/análogos & derivados , Fenilalanina/química , Fenilalanina/metabolismo , Fenilalanina/farmacologia , Compostos de Fenilureia/química , Compostos de Fenilureia/metabolismo , Compostos de Fenilureia/farmacologia , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas , Redobramento de Proteína , Estabilidade Proteica , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/metabolismo , Células Th17/efeitos dos fármacos , Células Th17/metabolismoRESUMO
Integrin-dependent adhesions are mechanosensitive structures in which talin mediates a linkage to actin filaments either directly or indirectly by recruiting vinculin. Here, we report the development and validation of a talin tension sensor. We find that talin in focal adhesions is under tension, which is higher in peripheral than central adhesions. Tension on talin is increased by vinculin and depends mainly on actin-binding site 2 (ABS2) within the middle of the rod domain, rather than ABS3 at the far C terminus. Unlike vinculin, talin is under lower tension on soft substrates. The difference between central and peripheral adhesions requires ABS3 but not vinculin or ABS2. However, differential stiffness sensing by talin requires ABS2 but not vinculin or ABS3. These results indicate that central versus peripheral adhesions must be organized and regulated differently, and that ABS2 and ABS3 have distinct functions in spatial variations and stiffness sensing. Overall, these results shed new light on talin function and constrain models for cellular mechanosensing.
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Mecanotransdução Celular , Talina/fisiologia , Citoesqueleto de Actina/metabolismo , Animais , Sítios de Ligação , Transferência Ressonante de Energia de Fluorescência , Adesões Focais , Camundongos , Modelos Biológicos , Células NIH 3T3 , Talina/metabolismo , Vinculina/metabolismo , Vinculina/fisiologiaRESUMO
Perioperative nurses at our institution voiced concerns about the amount of traffic in the ORs. We formed a workgroup consisting of perioperative nurses, educators, and leaders and initiated a quality improvement (QI) project to identify the amount of OR traffic that occurs during a procedure. The workgroup developed a check sheet to record door swings, staff classifications, reasons for opening the door, and the number of people in the OR at 15-minute intervals. Baseline results showed that average door swings ranged from 33 per hour in general surgery to 54 per hour in cardiac surgery. Nurses accounted for the most traffic, citing retrieving supplies as the main reason. Interventions focused on decreasing nurse traffic for retrieval of supplies in general surgery. Follow-up observations showed that average door swings increased to 41 per hour in general surgery, but nurse traffic decreased. Monitoring and limiting traffic could positively affect patient safety and outcomes.
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Salas Cirúrgicas/organização & administração , Conscientização , Salas Cirúrgicas/normas , Enfermagem Perioperatória , Melhoria de Qualidade , Desenvolvimento de PessoalRESUMO
The structure-based design, synthesis, and biological evaluation of a new pyrazole series of irreversible KAT II inhibitors are described herein. The modification of the inhibitor scaffold of 1 and 2 from a dihydroquinolinone core to a tetrahydropyrazolopyridinone core led to discovery of a new series of potent KAT II inhibitors with excellent physicochemical properties. Compound 20 is the most potent and lipophilically efficient of these new pyrazole analogs, with a k(inact)/K(i) value of 112,000 M(-1)s(-1) and lipophilic efficiency (LipE) of 8.53. The X-ray crystal structure of 20 with KAT II demonstrates key features that contribute to this remarkable potency and binding efficiency.
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Desenho de Fármacos , Inibidores Enzimáticos/farmacologia , Pirazóis/farmacologia , Transaminases/antagonistas & inibidores , Domínio Catalítico/efeitos dos fármacos , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Humanos , Interações Hidrofóbicas e Hidrofílicas/efeitos dos fármacos , Modelos Moleculares , Estrutura Molecular , Pirazóis/síntese química , Pirazóis/química , Relação Estrutura-Atividade , Transaminases/metabolismoRESUMO
Several protein engineering approaches were combined to optimize the selectivity and activity of Vibrio fluvialis aminotransferase (Vfat) for the synthesis of (3S,5R)-ethyl 3-amino-5-methyloctanoate; a key intermediate in the synthesis of imagabalin, an advanced candidate for the treatment of generalized anxiety disorder. Starting from wild-type Vfat, which had extremely low activity catalyzing the desired reaction, we engineered an improved enzyme with a 60-fold increase in initial reaction velocity for transamination of (R)-ethyl 5-methyl 3-oxooctanoate to (3S,5R)-ethyl 3-amino-5-methyloctanoate. To achieve this, <450 variants were screened, which allowed accurate assessment of enzyme performance using a low-throughput ultra performance liquid chromatography assay. During the course of this work, crystal structures of Vfat wild type and an improved variant (Vfat variant r414) were solved and they are reported here for the first time. This work also provides insight into the critical residues for substrate specificity for the transamination of (R)-ethyl 5-methyl 3-oxooctanoate and structurally related ß-ketoesters.
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Aminoácidos/metabolismo , Caprilatos/metabolismo , Engenharia de Proteínas/métodos , Transaminases/genética , Transaminases/metabolismo , Vibrio/enzimologia , Cinética , Modelos Moleculares , Mutação , Conformação Proteica , Homologia de Sequência de Aminoácidos , Especificidade por Substrato , Transaminases/químicaRESUMO
A series of aryl hydroxamates recently have been disclosed as irreversible inhibitors of kynurenine amino transferase II (KAT II), an enzyme that may play a role in schizophrenia and other psychiatric and neurological disorders. The utilization of structure-activity relationships (SAR) in conjunction with X-ray crystallography led to the discovery of hydroxamate 4, a disubstituted analogue that has a significant potency enhancement due to a novel interaction with KAT II. The use of k inact/K i to assess potency was critical for understanding the SAR in this series and for identifying compounds with improved pharmacodynamic profiles.
RESUMO
Kynurenine aminotransferase (KAT) II has been identified as a potential new target for the treatment of cognitive impairment associated with schizophrenia and other psychiatric disorders. Following a high-throughput screen, cyclic hydroxamic acid PF-04859989 was identified as a potent and selective inhibitor of human and rat KAT II. An X-ray crystal structure and (13)C NMR studies of PF-04859989 bound to KAT II have demonstrated that this compound forms a covalent adduct with the enzyme cofactor, pyridoxal phosphate (PLP), in the active site. In vivo pharmacokinetic and efficacy studies in rat show that PF-04859989 is a brain-penetrant, irreversible inhibitor and is capable of reducing brain kynurenic acid by 50% at a dose of 10 mg/kg (sc). Preliminary structure-activity relationship investigations have been completed and have identified the positions on this scaffold best suited to modification for further optimization of this novel series of KAT II inhibitors.
RESUMO
Inhibition of acetyl-CoA carboxylases (ACCs), a crucial enzyme for fatty acid metabolism, has been shown to promote fatty acid oxidation and reduce body fat in animal models. Therefore, ACCs are attractive targets for structure-based inhibitor design, particularly the carboxyltransferase (CT) domain, which is the primary site for inhibitor interaction. We have cloned, expressed, and purified the CT domain of human ACC2 using baculovirus-mediated insect cell expression system. However, attempts to crystallize the human ACC2 CT domain have not been successful in our hands. Hence, we have been using the available crystal structure of yeast CT domain to design human ACC inhibitors. Unfortunately, as the selectivity of the lead series has increased against the full-length human enzyme, the potency against the yeast enzyme has decreased significantly. This loss of potency against the yeast enzyme correlated with a complete lack of binding of the human-specific compounds to crystals of the yeast CT domain. Here, we address this problem by converting nine key active site residues of the yeast CT domain to the corresponding human residues. The resulting humanized yeast ACC-CT (yCT-H9) protein exhibits biochemical and biophysical properties closer to the human CT domain and binding to human specific compounds. We report high resolution crystal structures of yCT-H9 complexed with inhibitors that show a preference for the human CT domain. These structures offer insights that explain the species selectivity of ACC inhibitors and may guide future drug design programs.
Assuntos
Acetil-CoA Carboxilase/antagonistas & inibidores , Acetil-CoA Carboxilase/química , Domínio Catalítico , Inibidores Enzimáticos/química , Proteínas de Saccharomyces cerevisiae/antagonistas & inibidores , Proteínas de Saccharomyces cerevisiae/química , Acetil-CoA Carboxilase/genética , Animais , Linhagem Celular , Cristalografia por Raios X , Desenho de Fármacos , Humanos , Saccharomyces cerevisiae , Proteínas de Saccharomyces cerevisiae/genética , Especificidade da Espécie , Spodoptera , Homologia Estrutural de Proteína , Relação Estrutura-AtividadeRESUMO
Mycobacteriophages are viruses that infect mycobacterial hosts such as Mycobacterium smegmatis and Mycobacterium tuberculosis. All mycobacteriophages characterized to date are dsDNA tailed phages, and have either siphoviral or myoviral morphotypes. However, their genetic diversity is considerable, and although sixty-two genomes have been sequenced and comparatively analyzed, these likely represent only a small portion of the diversity of the mycobacteriophage population at large. Here we report the isolation, sequencing and comparative genomic analysis of 18 new mycobacteriophages isolated from geographically distinct locations within the United States. Although no clear correlation between location and genome type can be discerned, these genomes expand our knowledge of mycobacteriophage diversity and enhance our understanding of the roles of mobile elements in viral evolution. Expansion of the number of mycobacteriophages grouped within Cluster A provides insights into the basis of immune specificity in these temperate phages, and we also describe a novel example of apparent immunity theft. The isolation and genomic analysis of bacteriophages by freshman college students provides an example of an authentic research experience for novice scientists.