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Maldonado-Hernández R, Quesada O, González-Feliciano JA, Baerga-Ortiz A, Lasalde-Dominicci JA. Identification of the native Torpedo californica nicotinic acetylcholine receptor's glycan composition after a multi-step sequential purification method using MALDI-ToF MS. Proteomics 2024; 24:e2300151. [PMID: 37904306 DOI: 10.1002/pmic.202300151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 09/18/2023] [Accepted: 10/09/2023] [Indexed: 11/01/2023]
Abstract
The Cys-loop pentameric ligand-gated ion channels comprise a dynamic group of proteins that have been extensively studied for decades, yielding a wealth of findings at both the structural and functional levels. The nicotinic acetylcholine receptor (nAChR) is no exception, as it is part of this large protein family involved in proper organismal function. Our efforts have successfully produced a highly pure nAChR in detergent complex (nAChR-DC), enabling more robust studies to be conducted on it, including beginning to experiment with high-throughput crystallization. Our homogeneous product has been identified and extensively characterized with 100% identity using Nano Lc MS/MS and MALDI ToF/ToF for each nAChR subunit. Additionally, the N-linked glycans in the Torpedo californica-nAChR (Tc-nAChR) subunits have been identified. To study this, the Tc-nAChR subunits were digested with PNGase F and the released glycans were analyzed by MALDI-ToF. The MS results showed the presence of high-mannose N-glycan in all native Tc-nAChR subunits. Specifically, the oligommanose population Man8-9GlcNac2 with peaks at m/z 1742 and 1904 ([M + Na]+ ions) were observed.
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Affiliation(s)
- Rafael Maldonado-Hernández
- Department of Biology, Ponce Campus, University of Puerto Rico, Ponce, Puerto Rico, USA
- Molecular Sciences Research Center, University of Puerto Rico, San Juan, Puerto Rico, USA
| | - Orestes Quesada
- Molecular Sciences Research Center, University of Puerto Rico, San Juan, Puerto Rico, USA
- Department of Physical Sciences, Río Piedras Campus, University of Puerto Rico, San Juan, Puerto Rico, USA
| | | | - Abel Baerga-Ortiz
- Molecular Sciences Research Center, University of Puerto Rico, San Juan, Puerto Rico, USA
- Clinical Bioreagent Center, University of Puerto Rico, San Juan, Puerto Rico, USA
- Department of Biochemistry, Medical Sciences Campus, University of Puerto Rico, San Juan, Puerto Rico, USA
| | - José A Lasalde-Dominicci
- Molecular Sciences Research Center, University of Puerto Rico, San Juan, Puerto Rico, USA
- Clinical Bioreagent Center, University of Puerto Rico, San Juan, Puerto Rico, USA
- Department of Biology, Río Piedras Campus, University of Puerto Rico, San Juan, Puerto Rico, USA
- Institute of Neurobiology, University of Puerto Rico Medical Science Campus, San Juan, Puerto Rico, USA
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Pursuing High-Resolution Structures of Nicotinic Acetylcholine Receptors: Lessons Learned from Five Decades. Molecules 2021; 26:molecules26195753. [PMID: 34641297 PMCID: PMC8510392 DOI: 10.3390/molecules26195753] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 09/19/2021] [Accepted: 09/20/2021] [Indexed: 01/04/2023] Open
Abstract
Since their discovery, nicotinic acetylcholine receptors (nAChRs) have been extensively studied to understand their function, as well as the consequence of alterations leading to disease states. Importantly, these receptors represent pharmacological targets to treat a number of neurological and neurodegenerative disorders. Nevertheless, their therapeutic value has been limited by the absence of high-resolution structures that allow for the design of more specific and effective drugs. This article offers a comprehensive review of five decades of research pursuing high-resolution structures of nAChRs. We provide a historical perspective, from initial structural studies to the most recent X-ray and cryogenic electron microscopy (Cryo-EM) nAChR structures. We also discuss the most relevant structural features that emerged from these studies, as well as perspectives in the field.
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Alioth-Streichenberg CM, Bodmer DM, Waser PG. Pharmacokinetics and pharmacodynamics of obidoxime in sarin-poisoned rats. Toxicol Appl Pharmacol 1991; 108:509-19. [PMID: 2020972 DOI: 10.1016/0041-008x(91)90097-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The pharmacokinetics and pharmacodynamics of the oxime obidoxime (Toxogonin, 50 mg/kg iv) were investigated in anesthetized normal rats and in sarin-poisoned (50 micrograms/kg iv) rats. The kinetics were described by a two-compartment open model. The elimination half-life ranged from 35 min in normal rats to 86 min in sarin-poisoned rats. Obidoxime excretion occurred predominantly by the renal route, amounting to 4.6% of the administered dose in normal rats and to 0.9% in sarin-poisoned rats within the first hour of administration. The significantly diminished glomerular filtration rate confirmed the retardation of obidoxime excretion in sarin poisoning. The mean arterial blood pressure (MAP) response to obidoxime, measured in normal rats, was a transient hypotension, but to sarin an immediate hypertension. In sarin-poisoned rats the therapeutic sequence of administration of obidoxime and atropine (5 mg/kg iv) seemed to be important: the administration of atropine 10 min after and of obidoxime 20 min after sarin poisoning exerted a stabilizing effect on MAP. No serum albumin binding was found for obidoxime. Competition experiments at the isolated nicotinic receptor demonstrated the anticholinergic activity of obidoxime. The affinity of obidoxime was 1000 times smaller than that of acetylcholine. It is concluded that obidoxime, due to its prolonged residence time in the organism in sarin poisoning, exerts a "curare-like" inhibition and protection of the nicotinic acetylcholine receptor and, combined with atropine, a synergistic effect on blood pressure normalization.
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Raeber AJ, Riggio G, Waser PG. Purification and isolation of choline acetyltransferase from the electric organ of Torpedo marmorata by affinity chromatography. EUROPEAN JOURNAL OF BIOCHEMISTRY 1989; 186:487-92. [PMID: 2606102 DOI: 10.1111/j.1432-1033.1989.tb15233.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Choline acetyltransferase (EC 2.3.1.6) catalyzes the synthesis of the neurotransmitter acetylcholine from acetylcoenzyme A and choline. It has been purified from the electric organ of Torpedo marmorata by a new double-affinity chromatography. Our rapid and specific purification procedure includes affinity chromatography on CoA-Sepharose and then a second affinity chromatography on the enzyme's inhibitor [2-[3-(2-ammonioethoxy)-benzoyl]ethyl]trimethylammonium bromide coupled to Sepharose via a six-carbon spacer arm. The final enzyme preparation has been purified 7300-fold to a specific activity of 73 mumol acetylcholine formed min-1 mg protein-1. The isolated enzyme gave a single band on disc polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The relative molecular mass was determined to be 68,300 +/- 2100.
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Affiliation(s)
- A J Raeber
- Department of Pharmacology, University of Zurich, Switzerland
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Bodmer DM, Sin-Ren AC, Waser PG. [14C]chloroacetylcholine as an advantageous affinity label of the acetylcholine receptor. JOURNAL OF RECEPTOR RESEARCH 1987; 7:799-807. [PMID: 3450869 DOI: 10.3109/10799898709054562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The alkylating agent [14C]chloroacetylcholine perchlorate [( 14C] ClACh) was synthesized and used for affinity labelling of the nicotinic acetylcholine receptor from Torpedo marmorata. Solubilized and affinity-purified receptor proteins were reduced and alkylated according to the bromoacetylcholine-method. Covalent binding of [14C] ClACh to the cholinergic receptor proved to be specific and saturable, and occurred exclusively to the alpha-subunit. Halogen substitution of acetylcholine by chlorine and insertion of a 14C-isotope instead of the widely used 3H resulted in favourable properties of the affinity label.
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Affiliation(s)
- D M Bodmer
- Department of Pharmacology, University of Zurich, Switzerland
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