1
|
Reilkoff RA, Proper J, Wacker DA. The authors reply. Crit Care Med 2022; 50:e612-e613. [PMID: 35612460 DOI: 10.1097/ccm.0000000000005544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Ronald A Reilkoff
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, University of Minnesota Medical School, Minneapolis, MN
| | - Jennifer Proper
- Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN
| | - David A Wacker
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Internal Medicine, University of Minnesota Medical School, Minneapolis, MN
| |
Collapse
|
2
|
Puskarich MA, Ingraham NE, Merck LH, Driver BE, Wacker DA, Black LP, Jones AE, Fletcher CV, South AM, Murray TA, Lewandowski C, Farhat J, Benoit JL, Biros MH, Cherabuddi K, Chipman JG, Schacker TW, Guirgis FW, Voelker HT, Koopmeiners JS, Tignanelli CJ. Efficacy of Losartan in Hospitalized Patients With COVID-19-Induced Lung Injury: A Randomized Clinical Trial. JAMA Netw Open 2022; 5:e222735. [PMID: 35294537 PMCID: PMC8928006 DOI: 10.1001/jamanetworkopen.2022.2735] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 01/23/2022] [Indexed: 12/14/2022] Open
Abstract
Importance SARS-CoV-2 viral entry may disrupt angiotensin II (AII) homeostasis, contributing to COVID-19 induced lung injury. AII type 1 receptor blockade mitigates lung injury in preclinical models, although data in humans with COVID-19 remain mixed. Objective To test the efficacy of losartan to reduce lung injury in hospitalized patients with COVID-19. Design, Setting, and Participants This blinded, placebo-controlled randomized clinical trial was conducted in 13 hospitals in the United States from April 2020 to February 2021. Hospitalized patients with COVID-19 and a respiratory sequential organ failure assessment score of at least 1 and not already using a renin-angiotensin-aldosterone system (RAAS) inhibitor were eligible for participation. Data were analyzed from April 19 to August 24, 2021. Interventions Losartan 50 mg orally twice daily vs equivalent placebo for 10 days or until hospital discharge. Main Outcomes and Measures The primary outcome was the imputed arterial partial pressure of oxygen to fraction of inspired oxygen (Pao2:Fio2) ratio at 7 days. Secondary outcomes included ordinal COVID-19 severity; days without supplemental o2, ventilation, or vasopressors; and mortality. Losartan pharmacokinetics and RAAS components (AII, angiotensin-[1-7] and angiotensin-converting enzymes 1 and 2)] were measured in a subgroup of participants. Results A total of 205 participants (mean [SD] age, 55.2 [15.7] years; 123 [60.0%] men) were randomized, with 101 participants assigned to losartan and 104 participants assigned to placebo. Compared with placebo, losartan did not significantly affect Pao2:Fio2 ratio at 7 days (difference, -24.8 [95%, -55.6 to 6.1]; P = .12). Compared with placebo, losartan did not improve any secondary clinical outcomes and led to fewer vasopressor-free days than placebo (median [IQR], 9.4 [9.1-9.8] vasopressor-free days vs 8.7 [8.2-9.3] vasopressor-free days). Conclusions and Relevance This randomized clinical trial found that initiation of orally administered losartan to hospitalized patients with COVID-19 and acute lung injury did not improve Pao2:Fio2 ratio at 7 days. These data may have implications for ongoing clinical trials. Trial Registration ClinicalTrials.gov Identifier: NCT04312009.
Collapse
Affiliation(s)
- Michael A. Puskarich
- Department of Emergency Medicine, University of Minnesota, Minneapolis
- Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minnesota
| | - Nicholas E. Ingraham
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, University of Minnesota, Minneapolis
| | - Lisa H. Merck
- Department of Emergency Medicine, University of Florida College of Medicine, Gainesville
| | - Brian E. Driver
- Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minnesota
| | - David A. Wacker
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, University of Minnesota, Minneapolis
| | - Lauren Page Black
- Department of Emergency Medicine, University of Florida College of Medicine, Jacksonville
| | - Alan E. Jones
- Department of Emergency Medicine, University of Mississippi Medical Center, Jackson
| | | | - Andrew M. South
- Section of Nephrology, Department of Pediatrics, Wake Forest School of Medicine and Brenner Children's Hospital, Winston Salem, North Carolina
- Division of Public Health Sciences, Department of Epidemiology and Prevention, Wake Forest School of Medicine, Winston Salem, North Carolina
- Department of Surgery-Hypertension and Vascular Research, Wake Forest School of Medicine, Winston Salem, North Carolina
| | - Thomas A. Murray
- Department of Biostatistics, School of Public Health, University of Minnesota, Minneapolis
| | - Christopher Lewandowski
- Department of Emergency Medicine, Henry Ford Hospital, Wayne State University, Detroit, Michigan
| | - Joseph Farhat
- Department of Surgery, North Memorial Medical Center, Minneapolis, Minnesota
| | - Justin L. Benoit
- Department of Emergency Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Michelle H. Biros
- Department of Emergency Medicine, University of Minnesota, Minneapolis
| | - Kartik Cherabuddi
- Department of Emergency Medicine, University of Florida College of Medicine, Gainesville
| | | | - Timothy W. Schacker
- Division of Infectious Disease, Department of Medicine, University of Minnesota, Minneapolis
| | - Faheem W. Guirgis
- Department of Emergency Medicine, University of Florida College of Medicine, Jacksonville
| | - Helen T. Voelker
- Department of Biostatistics, School of Public Health, University of Minnesota, Minneapolis
| | - Joseph S. Koopmeiners
- Department of Biostatistics, School of Public Health, University of Minnesota, Minneapolis
| | | |
Collapse
|
3
|
Haley AC, Wacker DA. Cinematic virtual reality for anxiety management in mechanically ventilated patients: a feasibility and pilot study. Acute Crit Care 2022; 37:230-236. [PMID: 35172527 PMCID: PMC9184980 DOI: 10.4266/acc.2021.00843] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 09/04/2021] [Indexed: 11/30/2022] Open
Abstract
Background Mechanically ventilated patients experience anxiety for many reasons. Pharmacological treatments such as benzodiazepines are commonly employed to manage anxiety; however, these therapies often cause undesired side effects. Additional therapies for anxiety management are needed. We sought to determine whether cell phone-based virtual reality therapy could feasibly be used for anxiety management in mechanically ventilated patients. Methods Mechanically ventilated subjects underwent at least one session of virtual reality therapy in which they were shown a cinematic video of an outdoor green space or blue space with 360° visual range of motion. Goal session duration was 5 minutes. The primary outcome was incidence of predefined patient safety events, including self-extubation and accidental removal of tubes or lines. Results Ten subjects underwent a total of 18 virtual reality sessions. Fifteen sessions lasted the planned 5 minutes, one session was extended at participant request, and two sessions were terminated early at participant request. There were no occurrences of the predefined safety events, and no occurrences of cybersickness. Use of a visual analog scale to measure anxiety level was feasible for this pilot study, demonstrating feasibility of this scale for future, larger scale studies. Conclusions Virtual reality therapy shows potential as a means of managing anxiety in patients undergoing mechanical ventilation, and further rigorous exploration with this protocol is feasible.
Collapse
|
4
|
Puskarich MA, Cummins NW, Ingraham NE, Wacker DA, Reilkoff RA, Driver BE, Biros MH, Bellolio F, Chipman JG, Nelson AC, Beckman K, Langlois R, Bold T, Aliota MT, Schacker TW, Voelker HT, Murray TA, Koopmeiners JS, Tignanelli CJ. A multi-center phase II randomized clinical trial of losartan on symptomatic outpatients with COVID-19. EClinicalMedicine 2021; 37:100957. [PMID: 34195577 PMCID: PMC8225661 DOI: 10.1016/j.eclinm.2021.100957] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [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: 03/09/2021] [Revised: 05/17/2021] [Accepted: 05/25/2021] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The SARS-CoV-2 virus enters cells via Angiotensin-converting enzyme 2 (ACE2), disrupting the renin-angiotensin-aldosterone axis, potentially contributing to lung injury. Treatment with angiotensin receptor blockers (ARBs), such as losartan, may mitigate these effects, though induction of ACE2 could increase viral entry, replication, and worsen disease. METHODS This study represents a placebo-controlled blinded randomized clinical trial (RCT) to test the efficacy of losartan on outpatients with COVID-19 across three hospital systems with numerous community sites in Minnesota, U.S. Participants included symptomatic outpatients with COVID-19 not already taking ACE-inhibitors or ARBs, enrolled within 7 days of symptom onset. Patients were randomized to 1:1 losartan (25 mg orally twice daily unless estimated glomerular filtration rate, eGFR, was reduced, when dosing was reduced to once daily) versus placebo for 10 days, and all patients and outcome assesors were blinded. The primary outcome was all-cause hospitalization within 15 days. Secondary outcomes included functional status, dyspnea, temperature, and viral load. (clinicatrials.gov, NCT04311177, closed to new participants). FINDINGS From April to November 2020, 117 participants were randomized 58 to losartan and 59 to placebo, and all were analyzed under intent to treat principles. The primary outcome did not differ significantly between the two arms based on Barnard's test [losartan arm: 3 events (5.2% 95% CI 1.1, 14.4%) versus placebo arm: 1 event (1.7%; 95% CI 0.0, 9.1%)]; proportion difference -3.5% (95% CI -13.2, 4.8%); p = 0.32]. Viral loads were not statistically different between treatment groups at any time point. Adverse events per 10 patient days did not differ signifcantly [0.33 (95% CI 0.22-0.49) for losartan vs. 0.37 (95% CI 0.25-0.55) for placebo]. Due to a lower than expected hospitalization rate and low likelihood of a clinically important treatment effect, the trial was terminated early. INTERPRETATION In this multicenter blinded RCT for outpatients with mild symptomatic COVID-19 disease, losartan did not reduce hospitalizations, though assessment was limited by low event rate. Importantly, viral load was not statistically affected by treatment. This study does not support initiation of losartan for low-risk outpatients.
Collapse
Affiliation(s)
- Michael A. Puskarich
- Department of Emergency Medicine, University of Minnesota, Minneapolis, MN, USA
- Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, MN, USA
| | - Nathan W. Cummins
- Division of Infectious Diseases, Department of Medicine, Mayo Clinic, Rochester, MN, USA
| | - Nicholas E. Ingraham
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - David A. Wacker
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Ronald A. Reilkoff
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Brian E Driver
- Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, MN, USA
| | - Michelle H. Biros
- Department of Emergency Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Fernanda Bellolio
- Division of Infectious Diseases, Department of Medicine, Mayo Clinic, Rochester, MN, USA
| | | | - Andrew C. Nelson
- Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, USA
| | - Kenneth Beckman
- University of Minnesota Genomics Center, University of Minnesota, Minneapolis, MN, USA
| | - Ryan Langlois
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN, USA
| | - Tyler Bold
- Division of Infectious Diseases, Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Matthew T. Aliota
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Twin Cities, St. Paul, MN, USA
| | - Timothy W. Schacker
- Division of Infectious Diseases, Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Helen T. Voelker
- Department of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN, USA
| | - Thomas A Murray
- Department of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN, USA
| | - Joseph S. Koopmeiners
- Department of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN, USA
| | - Christopher J. Tignanelli
- Department of Emergency Medicine, Mayo Clinic, Rochester, MN, USA
- Department of Surgery, University of Minnesota, Minneapolis, MN, USA
| |
Collapse
|
5
|
Nwigwe IJ, Kim YJ, Wacker DA, Kim TH. Boundary Associated Long Noncoding RNA Mediates Long-Range Chromosomal Interactions. PLoS One 2015; 10:e0136104. [PMID: 26302455 PMCID: PMC4547746 DOI: 10.1371/journal.pone.0136104] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 07/29/2015] [Indexed: 11/17/2022] Open
Abstract
CCCTC binding factor (CTCF) is involved in organizing chromosomes into mega base-sized, topologically associated domains (TADs) along with other factors that define sub-TAD organization. CTCF-Cohesin interactions have been shown to be critical for transcription insulation activity as it stabilizes long-range interactions to promote proper gene expression. Previous studies suggest that heterochromatin boundary activity of CTCF may be independent of Cohesin, and there may be additional mechanisms for defining topological domains. Here, we show that a boundary site we previously identified known as CTCF binding site 5 (CBS5) from the homeotic gene cluster A (HOXA) locus exhibits robust promoter activity. This promoter activity from the CBS5 boundary element generates a long noncoding RNA that we designate as boundary associated long noncoding RNA-1 (blncRNA1). Functional characterization of this RNA suggests that the transcript stabilizes long-range interactions at the HOXA locus and promotes proper expression of HOXA genes. Additionally, our functional analysis also shows that this RNA is not needed in the stabilization of CTCF-Cohesin interactions however CTCF-Cohesin interactions are critical in the transcription of blncRNA1. Thus, the CTCF-associated boundary element, CBS5, employs both Cohesin and noncoding RNA to establish and maintain topologically associated domains at the HOXA locus.
Collapse
Affiliation(s)
- Ifeoma Jane Nwigwe
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT, 06520, United States of America
| | - Yoon Jung Kim
- Center for Systems Biology and Department of Biological Sciences, The University of Texas at Dallas, Richardson, TX, 75080, United States of America
| | - David A. Wacker
- Departments of Internal and Emergency Medicine, University of Maryland School of Medicine, Baltimore, MD, 21201, United States of America
| | - Tae Hoon Kim
- Center for Systems Biology and Department of Biological Sciences, The University of Texas at Dallas, Richardson, TX, 75080, United States of America
| |
Collapse
|
6
|
Abstract
Critically ill patients with undifferentiated shock are complex and challenging cases in the ED. A systematic approach to assessment and management is essential to prevent unnecessary morbidity and mortality. The simplified, systematic approach described in this article focuses on determining the presence of problems with cardiac function (the pump), intravascular volume (the tank), or systemic vascular resistance (the pipes). With this approach, the emergency physician can detect life-threatening conditions and implement time-sensitive therapy.
Collapse
Affiliation(s)
- David A Wacker
- Emergency Medicine/Internal Medicine/Critical Care Program, University of Maryland Medical Center, 110 South Paca Street, 6th Floor, Suite 200, Baltimore, MD 21201, USA
| | - Michael E Winters
- Emergency Medicine/Internal Medicine/Critical Care Program, University of Maryland School of Medicine, 110 South Paca Street, 6th Floor, Suite 200, Baltimore, MD 21201, USA.
| |
Collapse
|
7
|
|
8
|
Wacker DA, Ruhl DD, Balagamwala EH, Hope KM, Zhang T, Kraus WL. The DNA binding and catalytic domains of poly(ADP-ribose) polymerase 1 cooperate in the regulation of chromatin structure and transcription. Mol Cell Biol 2007; 27:7475-85. [PMID: 17785446 PMCID: PMC2169059 DOI: 10.1128/mcb.01314-07] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We explored the mechanisms of chromatin compaction and transcriptional regulation by poly(ADP-ribose) polymerase 1 (PARP-1), a nucleosome-binding protein with an NAD(+)-dependent enzymatic activity. By using atomic force microscopy and a complementary set of biochemical assays with reconstituted chromatin, we showed that PARP-1 promotes the localized compaction of chromatin into supranucleosomal structures in a manner independent of the amino-terminal tails of core histones. In addition, we defined the domains of PARP-1 required for nucleosome binding, chromatin compaction, and transcriptional repression. Our results indicate that the DNA binding domain (DBD) of PARP-1 is necessary and sufficient for binding to nucleosomes, yet the DBD alone is unable to promote chromatin compaction and only partially represses RNA polymerase II-dependent transcription in an in vitro assay with chromatin templates (approximately 50% of the repression observed with wild-type PARP-1). Furthermore, our results show that the catalytic domain of PARP-1, which does not bind nucleosomes on its own, cooperates with the DBD to promote chromatin compaction and efficient transcriptional repression in a manner independent of its enzymatic activity. Collectively, our results have revealed a novel function for the catalytic domain in chromatin compaction. In addition, they show that the DBD and catalytic domain cooperate to regulate chromatin structure and chromatin-dependent transcription, providing mechanistic insights into how these domains contribute to the chromatin-dependent functions of PARP-1.
Collapse
Affiliation(s)
- David A Wacker
- Department of Molecular Biology and Genetics, Cornell University, 465 Biotechnology Building, Ithaca, NY 14853, USA
| | | | | | | | | | | |
Collapse
|
9
|
Wacker DA, Frizzell KM, Zhang T, Kraus WL. Regulation of chromatin structure and chromatin-dependent transcription by poly(ADP-ribose) polymerase-1: possible targets for drug-based therapies. Subcell Biochem 2007; 41:45-69. [PMID: 17484123 DOI: 10.1007/1-4020-5466-1_3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Poly(ADP-ribose) Polymerase-1 (PARP-1) is the prototypical and most abundantly expressed member of a family of PARPs that catalyze the polymerization of ADP-ribose (ADPR) units from donor NAD' molecules on target proteins. PARP-1 plays roles in a variety of genomic processes, including the regulation of chromatin structure and transcription in response to specific cellular signals. PARP-1 also plays important roles in many stress-induced disease states. In this chapter, we review the molecular and cellular aspects of PARP-1's chromatin-modulating activities, as well as the impact that these chromatin-modulating activities have on the regulation of gene expression. In addition, we highlight the potential therapeutic use of drugs that target PARP-1's enzymatic activity for the treatment of human diseases
Collapse
Affiliation(s)
- David A Wacker
- Department of Molecular Biology and Genetics, Cornell University, 465 Biotechnology Building, Ithaca, NY 14853, USA
| | | | | | | |
Collapse
|
10
|
Brower-Toland B, Wacker DA, Fulbright RM, Lis JT, Kraus WL, Wang MD. Specific contributions of histone tails and their acetylation to the mechanical stability of nucleosomes. J Mol Biol 2004; 346:135-46. [PMID: 15663933 DOI: 10.1016/j.jmb.2004.11.056] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 11/21/2004] [Accepted: 11/22/2004] [Indexed: 12/22/2022]
Abstract
The distinct contributions of histone tails and their acetylation to nucleosomal stability were examined by mechanical disruption of individual nucleosomes in a single chromatin fiber using an optical trap. Enzymatic removal of H2A/H2B tails primarily decreased the strength of histone-DNA interactions located approximately +/-36bp from the dyad axis of symmetry (off-dyad strong interactions), whereas removal of the H3/H4 tails played a greater role in regulating the total amount of DNA bound. Similarly, nucleosomes composed of histones acetylated to different degrees by the histone acetyltransferase p300 exhibited significant decreases in the off-dyad strong interactions and the total amount of DNA bound. Acetylation of H2A/H2B appears to play a particularly critical role in weakening the off-dyad strong interactions. Collectively, our results suggest that the destabilizing effects of tail acetylation may be due to elimination of specific key interactions in the nucleosome.
Collapse
Affiliation(s)
- Brent Brower-Toland
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853, USA
| | | | | | | | | | | |
Collapse
|
11
|
Willis CL, Wacker DA, Bartlett RD, Bleakman D, Lodge D, Chamberlin AR, Bridges RJ. Irreversible inhibition of high-affinity [3H]kainate binding by a novel photoactivatable analogue: (2'S,3'S,4'R)-2'-carboxy-4'-(2-diazo-1-oxo-3, 3,3-trifluoropropyl)-3'-pyrrolidinyl acetate. J Neurochem 1997; 68:1503-10. [PMID: 9084420 DOI: 10.1046/j.1471-4159.1997.68041503.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A photolabile trifluoromethyldiazoketone derivative of kainate (KA), (2'S,3'S,4'R)-2'-carboxy-4'-(2-diazo-1-oxo-3, 3,3-trifluoropropyl)-3'-pyrrolidinyl acetate (DZKA), was synthesized and evaluated as an irreversible inhibitor of the high-affinity KA site on rat forebrain synaptic plasma membranes (SPMs). In the absence of UV irradiation, DZKA preferentially blocked [3H]KA binding with an IC50 of 0.63 microM, a concentration that produced little or no inhibition at AMPA or NMDA sites. At 100 microM, however, DZKA inhibited [3H]AMPA and L-[3H]glutamate binding by approximately 50%. When examined electrophysiologically in HEK293 cells expressing human KA (GluR6) or AMPA (GluR1) subtypes, DZKA acted preferentially at KA receptors as a weak agonist. DZKA also exhibited little or no excitotoxic activity in mixed rat cortical cultures. Irreversible inhibition was assessed by pretreating SPMs with DZKA (50 microM) in the presence of UV irradiation, removing unbound DZKA, and then assaying the reisolated SPMs for radioligand binding. This protocol produced a selective and irreversible loss of approximately 50% of the [3H]KA sites. The binding was recoverable in SPMs pretreated with DZKA or UV alone. Coincubation with L-glutamate prevented the loss in [3H]KA binding, suggesting that the inactivation occurred at or near the ligand binding site. These results are consistent with the action of DZKA as a photoaffinity ligand for the KA site and identify the analogue as a valuable probe for future investigations of receptor structure and function.
Collapse
Affiliation(s)
- C L Willis
- Department of Pharmaceutical Sciences, School of Pharmacy and Allied Health Sciences, University of Montana, Missoula 59812, USA
| | | | | | | | | | | | | |
Collapse
|
12
|
Bain JD, Diala ES, Glabe CG, Wacker DA, Lyttle MH, Dix TA, Chamberlin AR. Site-specific incorporation of nonnatural residues during in vitro protein biosynthesis with semisynthetic aminoacyl-tRNAs. Biochemistry 1991; 30:5411-21. [PMID: 2036409 DOI: 10.1021/bi00236a013] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A method is presented for the incorporation of nonnatural amino acids into proteins during in vitro cell-free translation. A combination of chemical synthesis and run-off transcription was employed to prepare a semisynthetic, nonhypermodified tRNA(Gly) nonsense suppressor acylated with L-3-[125I]iodotyrosine. The presence of this synthetic tRNA during in vitro translation of mRNA containing a nonsense suppression site (e.g., a UAG termination codon) results in the incorporation of the nonnatural amino acid L-3-iodotyrosine into the polypeptide exclusively at the position corresponding to that site. Incorporation of the nonnatural amino acid L-3-[125I]iodotyrosine into the model polypeptide was assessed by quantitative and unambiguous determination of suppression efficiency, read-through, and site specificity of incorporation. Minor modifications of the method employed in this initial experiment also allow the rapid analysis of unlabeled acylated tRNA analogues. Under optimum conditions, the unlabeled amino acid L-3-iodotyrosine was found to be incorporated with a suppression efficiency of 65%. Other nonnatural residues, including N-methylphenylalanine, D-phenylalanine, and phenyllactic acid, were tested in the assay under these same conditions. Suppression efficiencies for this series ranged from 0 to 72% depending on the structure of the residue incorporated. Several other aspects of this methodology, such as tRNA structure and context effects, are briefly discussed.
Collapse
Affiliation(s)
- J D Bain
- Department of Biological Chemistry, University of California, Irvine 92717
| | | | | | | | | | | | | |
Collapse
|