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Coriddi M, Burke EA, Myers P, Soudant C, McCarthy CM. Autoimmune Disease and Breast Implants: Systematic Review of Outcomes. Ann Plast Surg 2023; 90:385-388. [PMID: 34117137 PMCID: PMC8660949 DOI: 10.1097/sap.0000000000002930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
ABSTRACT Given that the use of breast implants for both cosmetic and reconstructive purposes is growing in the United States, an evaluation of factors that may affect the outcome of breast implant surgery is needed. A systematic review was conducted to evaluate the question: Does a personal or family history of autoimmune disease affect outcomes in breast implant surgery? The literature search yielded 2425 records, but after removal of duplicates, abstract screening, and full-text assessment, only 2 studies met the inclusion criteria for the final review. Both studies provided level III evidence and the average Methodological Index for Non-Randomized Studies score was 16.5 (range, 15-18 of 24), indicating a fair level of evidence overall. This systematic review found no evidence to support that a diagnosis of an autoimmune disease and/or a family history of autoimmune diseases will lead to poor surgical outcomes in breast implant surgery. Further study is warranted.
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Affiliation(s)
- Michelle Coriddi
- Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY
| | - Elizabeth Anne Burke
- Division of Plastic and Reconstructive Surgery, NorthShore University HealthSystem, Chicago, IL
| | - Paige Myers
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI
| | - Celine Soudant
- Medical Library, Memorial Sloan Kettering Cancer Center, New York, NY
| | - Colleen M. McCarthy
- Plastic and Reconstructive Surgery Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY
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2
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Liu C, Debnath N, Mosoyan G, Chauhan K, Vasquez-Rios G, Soudant C, Menez S, Parikh CR, Coca SG. Systematic Review and Meta-Analysis of Plasma and Urine Biomarkers for CKD Outcomes. J Am Soc Nephrol 2022; 33:1657-1672. [PMID: 35858701 PMCID: PMC9529190 DOI: 10.1681/asn.2022010098] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 06/02/2022] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Sensitive and specific biomarkers are needed to provide better biologic insight into the risk of incident and progressive CKD. However, studies have been limited by sample size and design heterogeneity. METHODS In this assessment of the prognostic value of preclinical plasma and urine biomarkers for CKD outcomes, we searched Embase (Ovid), MEDLINE ALL (Ovid), and Scopus up to November 30, 2020, for studies exploring the association between baseline kidney biomarkers and CKD outcomes (incident CKD, CKD progression, or incident ESKD). We used random-effects meta-analysis. RESULTS After screening 26,456 abstracts and 352 full-text articles, we included 129 studies in the meta-analysis for the most frequently studied plasma biomarkers (TNFR1, FGF23, TNFR2, KIM-1, suPAR, and others) and urine biomarkers (KIM-1, NGAL, and others). For the most frequently studied plasma biomarkers, pooled RRs for CKD outcomes were 2.17 (95% confidence interval [95% CI], 1.91 to 2.47) for TNFR1 (31 studies); 1.21 (95% CI, 1.15 to 1.28) for FGF-23 (30 studies); 2.07 (95% CI, 1.82 to 2.34) for TNFR2 (23 studies); 1.51 (95% CI, 1.38 to 1.66) for KIM-1 (18 studies); and 1.42 (95% CI, 1.30 to 1.55) for suPAR (12 studies). For the most frequently studied urine biomarkers, pooled RRs were 1.10 (95% CI, 1.05 to 1.16) for KIM-1 (19 studies) and 1.12 (95% CI, 1.06 to 1.19) for NGAL (19 studies). CONCLUSIONS Studies of preclinical biomarkers for CKD outcomes have considerable heterogeneity across study cohorts and designs, limiting comparisons of prognostic performance across studies. Plasma TNFR1, FGF23, TNFR2, KIM-1, and suPAR were among the most frequently investigated in the setting of CKD outcomes.
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Affiliation(s)
- Caroline Liu
- Department of Medical Education, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Neha Debnath
- Department of Medicine, Icahn School of Medicine at Mount Sinai (Morningside/West), New York, New York
| | - Gohar Mosoyan
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Kinsuk Chauhan
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - George Vasquez-Rios
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Celine Soudant
- Division of Technology, Memorial Sloan Kettering Cancer Center Medical Library, New York, New York
| | - Steve Menez
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Chirag R. Parikh
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Steven G. Coca
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
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Coughlin AC, Ahsanuddin S, Inglesby D, Fox C, Xu H, Margulies I, Sayegh F, Soudant C, Sacks HS, Kaufman A, Taub PJ. "When to Nuss? patient age as a risk factor for complications of minimally invasive repair of pectus excavatum: a systematic review and meta-analysis". Pediatr Surg Int 2022; 38:365-375. [PMID: 35006367 DOI: 10.1007/s00383-021-05049-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/20/2021] [Indexed: 11/28/2022]
Abstract
PURPOSE The optimal age for minimally invasive repair of pectus excavatum (MIRPE) is unclear; this study investigates the differences in complication rates among different age groups undergoing repair. METHODS PubMed and Embase databases were searched from inception to October 2020. To assess age as a risk factor for complications, odds ratios from relevant studies were analyzed using the Mantel-Haenszel method with a random-effects model for younger vs older patients. Specific complication rates were compared between the two cohorts using a chi-squared test. RESULTS Of the 4448 studies retrieved, 25 studies stratified complication data by age groups. From these studies, ten studies compared groups at ages < 18 and ≥ 18 and four studies compared ages < 20 and ≥ 20, and one study compared ages < 19 and ≥ 19. These fifteen studies reported on 5978 patients, with 1188 complications, for a complication rate of 19.87%. Older patients were more likely to have complications in a pooled analysis of studies comparing older vs younger patients (OR = 1.66, 95% CI = 1.28-2.14, heterogeneity I2 = 49%). Specifically, older patients were significantly more likely to experience pneumothorax, pleural effusion, wound infection, bar displacement, and reoperations. CONCLUSION Increased age is a risk factor for complications of MIRPE. This supports repair of pectus excavatum prior to late adolescence.
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Affiliation(s)
- Arielle C Coughlin
- Division of Surgery, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
| | - Sofia Ahsanuddin
- Division of Surgery, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
| | - Dani Inglesby
- Division of Surgery, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
| | - Conner Fox
- Division of Surgery, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
| | - Hope Xu
- Division of Surgery, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
| | - Ilana Margulies
- Division of Surgery, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
| | - Farah Sayegh
- Division of Surgery, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
| | - Celine Soudant
- Levy Library, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Henry S Sacks
- Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Andrew Kaufman
- Department of Thoracic Surgery, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Peter J Taub
- Division of Surgery, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA.
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Agrawal M, Sabino J, Frias-Gomes C, Hillenbrand CM, Soudant C, Axelrad JE, Shah SC, Ribeiro-Mourão F, Lambin T, Peter I, Colombel JF, Narula N, Torres J. Early life exposures and the risk of inflammatory bowel disease: Systematic review and meta-analyses. EClinicalMedicine 2021; 36:100884. [PMID: 34308303 PMCID: PMC8257976 DOI: 10.1016/j.eclinm.2021.100884] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 04/12/2021] [Accepted: 04/16/2021] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Early life exposures impact immune system development and therefore the risk of immune-mediated diseases, including inflammatory bowel disease (IBD). We systematically reviewed the impact of pre-, peri‑, and postnatal exposures up to the age of five years on subsequent IBD diagnosis. METHODS We identified case-control and cohort studies reporting on the association between early life environmental factors and Crohn's disease (CD), ulcerative colitis (UC), or IBD overall. Databases were search from their inception until May 24th, 2019 until July 14th, 2020. We conducted meta-analyses for quantitative review of relevant risk factors that were comparable across studies and qualitative synthesis of the literature for a wide range of early life exposures, including maternal health and exposures during pregnancy, perinatal factors, birth month and related-factors, breastfeeding, hygiene-related factors and social factors, immigration, antibiotics, offspring health, including infections, and passive smoking. PROSPERO registration: CRD42019134980. FINDINGS Prenatal exposure to antibiotics (OR 1.8; 95% CI 1.2-2.5) and tobacco smoke (OR 1.5; 95% CI 1.2-1.9), and early life otitis media (OR 2.1; 95% CI 1.2-3.6) were associated with IBD. There was a trend towards an association between exposure to antibiotics in infancy and IBD (OR: 1.7, 95% CI 0.97, 2.9), supported by positive data on population-based data. Breastfeeding was protective against IBD. Other early life risk factors had no association with IBD, but data were limited and heterogenous. INTERPRETATION Early life is an important period of susceptibility for IBD development later in life. Tobacco smoke, infections and antibiotics were associated positively, and breastfeeding was associated negatively with IBD. Our findings offer an opportunity to develop primary prevention strategies. FUNDING This study did not receive any funding.
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Affiliation(s)
- Manasi Agrawal
- The Henry D. Janowitz Division of Gastroenterology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - João Sabino
- Gastroenterology Division, University Hospital of Leuven, Leuven, Belgium
| | - Catarina Frias-Gomes
- Division of Gastroenterology, Hospital Beatriz Ângelo, Loures 2674-514, Portugal
| | - Christen M. Hillenbrand
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Celine Soudant
- Levy Library, The Mount Sinai Medical Center, New York, NY, United States
- Medical Library, Memorial Sloan Kettering Cancer Center, New York, NY, United States
| | - Jordan E. Axelrad
- Division of Gastroenterology, New York University Grossman School of Medicine, New York, NY, United States
| | - Shailja C. Shah
- Division of Gastroenterology, Hepatology, and Nutrition, Vanderbilt University Medical Center, Nashville, TN, United States
- Section of Gastroenterology, Veterans Affairs Tennessee Valley Healthcare System, Nashville campus, Nashville, TN, United States
| | - Francisco Ribeiro-Mourão
- Pediatrics Department, Unidade Local de Saúde do Alto Minho, Viana do Castelo, Portugal
- Pediatrics Department, Centro Materno Infantil do Norte – Centro Hospitalar e Universitário do Porto, Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar, University of Porto, Porto, Portugal
| | - Thomas Lambin
- Department of Gastroenterology, Claude Huriez Hospital, University of Lille, Lille, France
| | - Inga Peter
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Jean-Frederic Colombel
- The Henry D. Janowitz Division of Gastroenterology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Neeraj Narula
- Department of Medicine (Division of Gastroenterology) and Farncombe Family Digestive, Health Research Institute, McMaster University, Hamilton, ON, Canada
| | - Joana Torres
- The Henry D. Janowitz Division of Gastroenterology, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Division of Gastroenterology, Hospital Beatriz Ângelo, Loures 2674-514, Portugal
- Faculdade de Medicina, Universidade de Lisboa, Portugal
- Corresponding author.
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Yeshokumar AK, Coughlin A, Fastman J, Psaila K, Harmon M, Randell T, Schorr EM, Han H, Hoang H, Soudant C, Jette N. Seizures in autoimmune encephalitis-A systematic review and quantitative synthesis. Epilepsia 2021; 62:397-407. [PMID: 33475161 DOI: 10.1111/epi.16807] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 12/15/2020] [Accepted: 12/15/2020] [Indexed: 12/20/2022]
Abstract
OBJECTIVE This study aimed to evaluate the proportion of patients with seizures and electroencephalography (EEG) abnormalities in autoimmune encephalitis (AE) and its most common subtypes. METHODS This systematic review followed Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) standards and was registered with the International Prospective Register of Systematic Reviews (PROSPERO). We searched Medline All, Embase, and PsychINFO in Ovid from inception to June 2019 for articles pertaining to AE and seizure. Included studies reported seizure and/or EEG data in cohorts of ≥10 AE patients. Patient demographics, antibody type, seizure incidence, and EEG findings were extracted. Review of studies and data extraction were performed in duplicate. In addition to descriptive analysis, quantitative synthesis stratified by autoantibody subtype was performed with logistic regression and chi-square analyses. RESULTS Our search yielded 3856 abstracts: 1616 were selected for full-text review and 118 studies met eligibility criteria. Of 3722 antibody-positive AE patients, 2601 (69.9%) had clinical seizures during the course of their illness. Of the 2025 patients with antibody-positive AE and available EEG data, 1718 (84.8%) had some EEG abnormality (eg, epileptiform discharges, slowing, and so on). Anti- N-methyl-d-aspartate (NMDA) receptor encephalitis (anti-NMDARE) was the most commonly reported type of AE (1985/3722, 53.3%). Of the anti-NMDARE patients with available seizure or EEG data, 71.8% (n = 1425/1985) had clinical seizures during their illness, and 89.7% (n = 1172/1306) had EEG abnormalities. For all AE patients and in the anti-NMDARE subpopulation, seizures were more common in younger patients (p < .05). SIGNIFICANCE This systematic review provides an estimate of the proportion of AE patients with seizures, confirming the magnitude of seizure burden in this population. Prospective studies are needed to understand population-based prevalence of seizures, identify factors associated with seizures, and evaluate particular EEG findings as biomarkers of seizures and outcomes in AE.
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Affiliation(s)
- Anusha K Yeshokumar
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Arielle Coughlin
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jarrett Fastman
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Kendall Psaila
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Michael Harmon
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Taylor Randell
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Emily M Schorr
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Helen Han
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Hai Hoang
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Celine Soudant
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Nathalie Jette
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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Das A, Roy B, Bandyopadhyay D, Dasgupta S, Chakraborty S, Soudant C, Gulati M, Ray KK, Lavie CJ. Non-statin interventions in the prevention of cardiovascular events: Sex-based meta-analysis. Prog Cardiovasc Dis 2020; 63:228-232. [PMID: 32224114 DOI: 10.1016/j.pcad.2020.03.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Accepted: 03/22/2020] [Indexed: 10/24/2022]
Abstract
OBJECTIVE To explore the sex-specific association of non-statin classes of drugs in reducing cardiovascular outcomes. METHODS Published data search up to November 2019 reporting primary outcomes that approximate with major vascular events (MVEs) after treatment with non-statin group of drugs was performed. The primary outcome was the sex-specific association with MVEs. Random-effects meta-analysis was performed to estimate relative risk (RR) of the individual classes of therapies. RESULTS Seven Randomized Clinical Trials (RCTs) including 122,164 patients were included in our analysis. Four studies compared the Triglyceride (TG)-lowering group of drugs with placebo and 3 studies compared low-density lipoprotein cholesterol (LDL-c) lowering drugs with placebo. Overall, with non-statin drugs, there was no difference in the risk reduction of cardiovascular (CV) events between men (RR 0.86; 95% CI 0.79-0.94, p-value <0.001) and women (RR 0.88; 95% CI 0.83-0.93, p-value 0.91). However, TG targeting interventions showed no cardiovascular outcome benefits in men (RR 0.85; 95% CI 0.71-1.02, p-value <0.001) while no significant benefit was seen in women (RR 0.87; 95% CI 0.77-0.98, p value = 0.85). No such difference existed in non-statin LDL-c lowering group of drugs in between men (RR 0.88; 95% CI 0.81-0.94, p value = 0.18) and women (RR 0.88; 95% CI 0.82-0.94, p value = 0.46). However, lowering of TG was only associated with a higher risk reduction of CV events (RR 0.86; 95% CI 0.77-0.95, p value = 0.03) in the entire study population. CONCLUSION Non-statin group of drugs was effective in reducing adverse CV outcomes for both sexes. Lowering TG was associated with higher risk reduction in CV events in general.
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Affiliation(s)
- Avash Das
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA..
| | - Bhaskar Roy
- Department of Neurology, Division of Neuromuscular Medicine, Yale School of Medicine, New Haven, CT, USA
| | | | - Subhajit Dasgupta
- Department of Cardiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | | | - Celine Soudant
- Gustave L. and Janet W. Levy Library, Mount Sinai Health System, One Gustave L. Levy Place, New York, NY, USA
| | - Martha Gulati
- Division of Cardiology, University of Arizona, Phoenix, AZ, USA
| | - Kausik K Ray
- Imperial Centre for Cardiovascular Disease Prevention, Department of Primary Care and Public Health, Imperial College London, London, UK
| | - Carl J Lavie
- Cardiac Rehabilitation and Preventive Cardiology, John Ochsner Heart and Vascular Institute, Ochsner Clinical School - The University of Queensland School of Medicine, New Orleans, LA, USA
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Bhatia K, Modi VA, Narasimhan B, Joshi AA, Sud K, Wu L, Uberoi G, Aggarwal D, Soudant C, Haider S, Fox A. ASSESSING THE SAFETY AND CLINICAL OUTCOMES OF BETA-BLOCKERS IN PATIENTS WITH HEART FAILURE AND REDUCED EJECTION FRACTION WITH CONCOMITANT COCAINE USE: A META-ANALYSIS. J Am Coll Cardiol 2020. [DOI: 10.1016/s0735-1097(20)31550-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Abstract
Ultrastructural observations of the phloem of coconut palms affected by "hartrot" disease in Suriname have revealed the presence of the plant-infecting flagellate Phytomonas in mature sieve tubes. The occurrence of these flagellates during the earliest symptoms of the disease and the correlated increase and spread of the flagellates in the phloem as the disease progresses suggest that the organisms may be pathogenic to the palms.
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Law CJ, Almqvist J, Bernstein A, Goetz RM, Huang Y, Soudant C, Laaksonen A, Hovmöller S, Wang DN. Salt-bridge dynamics control substrate-induced conformational change in the membrane transporter GlpT. J Mol Biol 2008; 378:828-39. [PMID: 18395745 DOI: 10.1016/j.jmb.2008.03.029] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Revised: 03/05/2008] [Accepted: 03/13/2008] [Indexed: 10/22/2022]
Abstract
Active transport of substrates across cytoplasmic membranes is of great physiological, medical and pharmaceutical importance. The glycerol-3-phosphate (G3P) transporter (GlpT) of the E. coli inner membrane is a secondary active antiporter from the ubiquitous major facilitator superfamily that couples the import of G3P to the efflux of inorganic phosphate (P(i)) down its concentration gradient. Integrating information from a novel combination of structural, molecular dynamics simulations and biochemical studies, we identify the residues involved directly in binding of substrate to the inward-facing conformation of GlpT, thus defining the structural basis for the substrate-specificity of this transporter. The substrate binding mechanism involves protonation of a histidine residue at the binding site. Furthermore, our data suggest that the formation and breaking of inter- and intradomain salt bridges control the conformational change of the transporter that accompanies substrate translocation across the membrane. The mechanism we propose may be a paradigm for organophosphate:phosphate antiporters.
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Affiliation(s)
- Christopher J Law
- The Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, Department of Cell Biology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
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10
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Abstract
Secondary active transport of substrate across the cell membrane is crucial to many cellular and physiological processes. The crystal structure of one member of the secondary active transporter family, the sn-glycerol-3-phosphate (G3P) transporter (GlpT) of the inner membrane of Escherichia coli, suggests a mechanism for substrate translocation across the membrane that involves a rocker-switch-type movement of the protein. This rocker-switch mechanism makes two specific predictions with respect to kinetic behavior: the transport rate increases with the temperature, whereas the binding affinity of the transporter to a substrate is temperature-independent. In this work, we directly tested these two predictions by transport kinetics and substrate-binding experiments, integrating the data on this single system into a coherent set of observations. The transport kinetics of the physiologically relevant G3P-phosphate antiport reaction were characterized at different temperatures using both E. coli whole cells and GlpT reconstituted into proteoliposomes. Substrate-binding affinity of the transporter was measured using tryptophan fluorescence quenching in detergent solution. Indeed, the substrate transport velocity of GlpT increased dramatically with temperature. In contrast, neither the apparent Michaelis constant (Km) nor the apparent substrate-binding dissociation constant (Kd) showed temperature dependence. Moreover, GlpT-catalyzed G3P translocation exhibited a completely linear Arrhenius function with an activation energy of 35.2 kJ mol-1 for the transporter reconstituted into proteoliposomes, suggesting that the substrate-loaded transporter is delicately poised between the inward- and outward-facing conformations. When these results are taken together, they are in agreement with a rocker-switch mechanism for GlpT.
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Affiliation(s)
| | | | | | | | - Da-Neng Wang
- * To whom correspondence should be addressed. Telephone: (212) 263-8634. Fax: (212) 263-8951. E-mail:
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