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Zhan X, Liu Y, Jannu AJ, Huang S, Ye B, Wei W, Pandya PH, Ye X, Pollok KE, Renbarger JL, Huang K, Zhang J. Identify potential driver genes for PAX-FOXO1 fusion-negative rhabdomyosarcoma through frequent gene co-expression network mining. Front Oncol 2023; 13:1080989. [PMID: 36793601 PMCID: PMC9924292 DOI: 10.3389/fonc.2023.1080989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 01/12/2023] [Indexed: 02/03/2023] Open
Abstract
Background Rhabdomyosarcoma (RMS) is a soft tissue sarcoma usually originated from skeletal muscle. Currently, RMS classification based on PAX-FOXO1 fusion is widely adopted. However, compared to relatively clear understanding of the tumorigenesis in the fusion-positive RMS, little is known for that in fusion-negative RMS (FN-RMS). Methods We explored the molecular mechanisms and the driver genes of FN-RMS through frequent gene co-expression network mining (fGCN), differential copy number (CN) and differential expression analyses on multiple RMS transcriptomic datasets. Results We obtained 50 fGCN modules, among which five are differentially expressed between different fusion status. A closer look showed 23% of Module 2 genes are concentrated on several cytobands of chromosome 8. Upstream regulators such as MYC, YAP1, TWIST1 were identified for the fGCN modules. Using in a separate dataset we confirmed that, comparing to FP-RMS, 59 Module 2 genes show consistent CN amplification and mRNA overexpression, among which 28 are on the identified chr8 cytobands. Such CN amplification and nearby MYC (also resides on one of the above cytobands) and other upstream regulators (YAP1, TWIST1) may work together to drive FN-RMS tumorigenesis and progression. Up to 43.1% downstream targets of Yap1 and 45.8% of the targets of Myc are differentially expressed in FN-RMS vs. normal comparisons, which also confirmed the driving force of these regulators. Discussion We discovered that copy number amplification of specific cytobands on chr8 and the upstream regulators MYC, YAP1 and TWIST1 work together to affect the downstream gene co-expression and promote FN-RMS tumorigenesis and progression. Our findings provide new insights for FN-RMS tumorigenesis and offer promising targets for precision therapy. Experimental investigation about the functions of identified potential drivers in FN-RMS are in progress.
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Affiliation(s)
- Xiaohui Zhan
- Department of Bioinformatics, School of Basic Medicine, Chongqing Medical University, Chongqing, China
| | - Yusong Liu
- College of Intelligent Systems Science and Engineering, Harbin Engineering University, Harbin, China
| | - Asha Jacob Jannu
- Department of Biostatistics and Health Data Science, Indiana University, School of Medicine, Indianapolis, IN, United States
| | | | - Bo Ye
- Department of Bioinformatics, School of Basic Medicine, Chongqing Medical University, Chongqing, China
| | - Wei Wei
- Department of Bioinformatics, School of Basic Medicine, Chongqing Medical University, Chongqing, China
| | - Pankita H Pandya
- Department of Pediatrics, Indiana University, School of Medicine, Indianapolis, IN, United States
| | - Xiufen Ye
- College of Intelligent Systems Science and Engineering, Harbin Engineering University, Harbin, China
| | - Karen E Pollok
- Department of Pediatrics, Indiana University, School of Medicine, Indianapolis, IN, United States
| | - Jamie L Renbarger
- Department of Pediatrics, Indiana University, School of Medicine, Indianapolis, IN, United States
| | - Kun Huang
- Department of Biostatistics and Health Data Science, Indiana University, School of Medicine, Indianapolis, IN, United States
| | - Jie Zhang
- Department of Medical and Molecular Genetics, Indiana University, School of Medicine, Indianapolis, IN, United States
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Shi J, Chen N, Wang Z, Wang F, Tan Y, Tan S, Tong J, An H, Guo X, Zuo L, Wang X, Yang F, Luo X. Cholinergic receptor nicotinic beta 3 subunit polymorphisms and smoking in male Chinese patients with schizophrenia. EC PSYCHOLOGY AND PSYCHIATRY 2021; 10:11-23. [PMID: 34368810 PMCID: PMC8341072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
OBJECTIVE The aim of this study was to examine if cholinergic receptor nicotinic beta 3 subunit (CHRNB3) was a common genetic basis for both nicotine dependence and schizophrenia. METHODS Two CHRNB3 promoter single nucleotide polymorphisms (SNPs) were genotyped in 773 patients with schizophrenia and 302 healthy volunteers. Associations between smoking, schizophrenia, smoking+schizophrenia and CHRNB3 were analyzed. The mRNA expression of CHRNB3 in human brains was examined, and the expression correlations between CHRNB3 and dopaminergic and GABAergic receptor genes were evaluated. RESULTS The association between CHRNB3 and smoking was significant in the total sample, less significant in the smoking with schizophrenia, and suggestive in the smoking without schizophrenia. CHRNB3 had significant mRNA expression that was correlated with dopaminergic or GABAergic receptor expression in human brains. The two CHRNB3 SNPs had significant cis-acting regulatory effects on CHRNB3 mRNA expression. CONCLUSIONS Risk for smoking behavior was associated with CHRNB3. CHRNB3 mRNA is abundant in human brain and could play important role in the pathogenesis of smoking behavior.
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Affiliation(s)
- Jing Shi
- Beijing Hui Long Guan Hospital/Peking University HuiLongGuan Clinical Medical School, Beijing, 100096, China
| | - Nan Chen
- Beijing Hui Long Guan Hospital/Peking University HuiLongGuan Clinical Medical School, Beijing, 100096, China
| | - Zhiren Wang
- Beijing Hui Long Guan Hospital/Peking University HuiLongGuan Clinical Medical School, Beijing, 100096, China
| | - Fan Wang
- Beijing Hui Long Guan Hospital/Peking University HuiLongGuan Clinical Medical School, Beijing, 100096, China
| | - Yunlong Tan
- Beijing Hui Long Guan Hospital/Peking University HuiLongGuan Clinical Medical School, Beijing, 100096, China
| | - Shuping Tan
- Beijing Hui Long Guan Hospital/Peking University HuiLongGuan Clinical Medical School, Beijing, 100096, China
| | - Jinghui Tong
- Beijing Hui Long Guan Hospital/Peking University HuiLongGuan Clinical Medical School, Beijing, 100096, China
| | - Huimei An
- Beijing Hui Long Guan Hospital/Peking University HuiLongGuan Clinical Medical School, Beijing, 100096, China
| | - Xiaoyun Guo
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Lingjun Zuo
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Xiaoping Wang
- Department of Neurology, Shanghai TongRen Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200336, China
| | - Fude Yang
- Beijing Hui Long Guan Hospital/Peking University HuiLongGuan Clinical Medical School, Beijing, 100096, China
| | - Xingguang Luo
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06520, USA
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Liu W, Li MD. Insights Into Nicotinic Receptor Signaling in Nicotine Addiction: Implications for Prevention and Treatment. Curr Neuropharmacol 2018; 16:350-370. [PMID: 28762314 PMCID: PMC6018190 DOI: 10.2174/1570159x15666170801103009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 06/18/2017] [Accepted: 07/28/2017] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Nicotinic acetylcholine receptors (nAChRs) belong to the Cys-loop ligandgated ion-channel (LGIC) superfamily, which also includes the GABA, glycine, and serotonin receptors. Many nAChR subunits have been identified and shown to be involved in signal transduction on binding to them of either the neurotransmitter acetylcholine or exogenous ligands such as nicotine. The nAChRs are pentameric assemblies of homologous subunits surrounding a central pore that gates cation flux, and they are expressed at neuromuscular junctions throughout the nervous system. METHODS AND RESULTS Because different nAChR subunits assemble into a variety of pharmacologically distinct receptor subtypes, and different nAChRs are implicated in various physiological functions and pathophysiological conditions, nAChRs represent potential molecular targets for drug addiction and medical therapeutic research. This review intends to provide insights into recent advances in nAChR signaling, considering the subtypes and subunits of nAChRs and their roles in nicotinic cholinergic systems, including structure, diversity, functional allosteric modulation, targeted knockout mutations, and rare variations of specific subunits, and the potency and functional effects of mutations by focusing on their effects on nicotine addiction (NA) and smoking cessation (SC). Furthermore, we review the possible mechanisms of action of nAChRs in NA and SC based on our current knowledge. CONCLUSION Understanding these cellular and molecular mechanisms will lead to better translational and therapeutic operations and outcomes for the prevention and treatment of NA and other drug addictions, as well as chronic diseases, such as Alzheimer's and Parkinson's. Finally, we put forward some suggestions and recommendations for therapy and treatment of NA and other chronic diseases.
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Affiliation(s)
- Wuyi Liu
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University School of Medicine, Hangzhou, China.,School of Biological Sciences and Food Engineering, Fuyang Normal University, Fuyang, Anuhi 236041, China
| | - Ming D Li
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University School of Medicine, Hangzhou, China.,Research Center for Air Pollution and Health, Zhejiang University, Hangzhou, China.,Institute of NeuroImmune Pharmacology, Seton Hall University, South Orange, NJ, United States
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Lucero LM, Weltzin MM, Eaton JB, Cooper JF, Lindstrom JM, Lukas RJ, Whiteaker P. Differential α4(+)/(-)β2 Agonist-binding Site Contributions to α4β2 Nicotinic Acetylcholine Receptor Function within and between Isoforms. J Biol Chem 2015; 291:2444-59. [PMID: 26644472 DOI: 10.1074/jbc.m115.684373] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Indexed: 11/06/2022] Open
Abstract
Two α4β2 nicotinic acetylcholine receptor (α4β2-nAChR) isoforms exist with (α4)2(β2)3 and (α4)3(β2)2 subunit stoichiometries and high versus low agonist sensitivities (HS and LS), respectively. Both isoforms contain a pair of α4(+)/(-)β2 agonist-binding sites. The LS isoform also contains a unique α4(+)/(-)α4 site with lower agonist affinity than the α4(+)/(-)β2 sites. However, the relative roles of the conserved α4(+)/(-)β2 agonist-binding sites in and between the isoforms have not been studied. We used a fully linked subunit concatemeric nAChR approach to express pure populations of HS or LS isoform α4β2*-nAChR. This approach also allowed us to mutate individual subunit interfaces, or combinations thereof, on each isoform background. We used this approach to systematically mutate a triplet of β2 subunit (-)-face E-loop residues to their non-conserved α4 subunit counterparts or vice versa (β2HQT and α4VFL, respectively). Mutant-nAChR constructs (and unmodified controls) were expressed in Xenopus oocytes. Acetylcholine concentration-response curves and maximum function were measured using two-electrode voltage clamp electrophysiology. Surface expression was measured with (125)I-mAb 295 binding and was used to define function/nAChR. If the α4(+)/(-)β2 sites contribute equally to function, making identical β2HQT substitutions at either site should produce similar functional outcomes. Instead, highly differential outcomes within the HS isoform, and between the two isoforms, were observed. In contrast, α4VFL mutation effects were very similar in all positions of both isoforms. Our results indicate that the identity of subunits neighboring the otherwise equivalent α4(+)/(-)β2 agonist sites modifies their contributions to nAChR activation and that E-loop residues are an important contributor to this neighbor effect.
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Affiliation(s)
- Linda M Lucero
- From the Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013 and
| | - Maegan M Weltzin
- From the Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013 and
| | - J Brek Eaton
- From the Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013 and
| | - John F Cooper
- the Department of Neuroscience, University of Pennsylvania Medical School, Philadelphia, Pennsylvania 19104
| | - Jon M Lindstrom
- the Department of Neuroscience, University of Pennsylvania Medical School, Philadelphia, Pennsylvania 19104
| | - Ronald J Lukas
- From the Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013 and
| | - Paul Whiteaker
- From the Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013 and
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Wang J, Kuryatov A, Lindstrom J. Expression of cloned α6* nicotinic acetylcholine receptors. Neuropharmacology 2014; 96:194-204. [PMID: 25446669 DOI: 10.1016/j.neuropharm.2014.10.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 09/19/2014] [Accepted: 10/07/2014] [Indexed: 10/24/2022]
Abstract
Nicotinic acetylcholine receptors (AChRs) are ACh-gated ion channels formed from five homologous subunits in subtypes defined by their subunit composition and stoichiometry. Some subtypes readily produce functional AChRs in Xenopus oocytes and transfected cell lines. α6β2β3* AChRs (subtypes formed from these subunits and perhaps others) are not easily expressed. This may be because the types of neurons in which they are expressed (typically dopaminergic neurons) have unique chaperones for assembling α6β2β3* AChRs, especially in the presence of the other AChR subtypes. Because these relatively minor brain AChR subtypes are of major importance in addiction to nicotine, it is important for drug development as well as investigation of their functional properties to be able to efficiently express human α6β2β3* AChRs. We review the issues and progress in expressing α6* AChRs. This article is part of the Special Issue entitled 'The Nicotinic Acetylcholine Receptor: From Molecular Biology to Cognition'.
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Affiliation(s)
- Jingyi Wang
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Alexander Kuryatov
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Jon Lindstrom
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
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Thompson AJ, Lummis SCR. A single channel mutation alters agonist efficacy at 5-HT3A and 5-HT3AB receptors. Br J Pharmacol 2014; 170:391-402. [PMID: 23822584 PMCID: PMC3834762 DOI: 10.1111/bph.12287] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 05/27/2013] [Accepted: 06/14/2013] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE 5-HT3 receptors are composed of 5-HT3A subunits (homomeric receptors), or combinations of 5-HT3A and other 5-HT3 receptor subunits (heteromeric receptors, the best studied of which are 5-HT3AB receptors). Here we explore the effects of partial agonists at 5-HT3A and 5-HT3AB receptors, and the importance of a channel-lining residue in determining the efficacy of activation. EXPERIMENTAL APPROACH Wild type and mutant 5-HT3A and 5-HT3AB receptors were expressed in Xenopus oocytes and examined using two-electrode voltage-clamp, or expressed in HEK293 cells and examined using [3H]granisetron binding. KEY RESULTS Dopamine, quipazine and VUF10166 were partial agonists at wild type 5-HT3A and 5-HT3AB receptors, with quipazine and VUF10166 causing a long-lived (>20 min) inhibition of subsequent agonist responses. At 5-HT3A receptors, mCPBG was a partial agonist, but was a superagonist at 5-HT3AB receptors, as it produced a response 2.6× greater than that of 5-HT. A T6'S substitution in the 5-HT3A subunit decreased EC50 and increased Rmax of dopamine and quipazine at both homomeric and heteromeric receptors. The greatest changes were seen with VUF10166 at 5-HT3AT6'SB receptors, where it became a full agonist (EC50 = 7 nM) with an EC50 58-fold less than 5-HT (EC50 = 0.4 μM) and no longer caused inhibition of subsequent agonist responses. CONCLUSIONS AND IMPLICATIONS These results indicate that a mutation in the pore lining domain in both 5-HT3A and 5-HT3AB receptors alters the relative efficacy of a series of agonists, changing some (e.g. quipazine) from apparent antagonists to potent and efficacious agonists.
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Affiliation(s)
- A J Thompson
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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Limapichat W, Dougherty DA, Lester HA. Subtype-specific mechanisms for functional interaction between α6β4* nicotinic acetylcholine receptors and P2X receptors. Mol Pharmacol 2014; 86:263-74. [PMID: 24966348 PMCID: PMC4152909 DOI: 10.1124/mol.114.093179] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 06/24/2014] [Indexed: 11/22/2022] Open
Abstract
P2X receptors and nicotinic acetylcholine receptors (nAChRs) display functional and physical interactions in many cell types and heterologous expression systems, but interactions between α6β4-containing (α6β4*) nAChRs and P2X2 receptors and/or P2X3 receptors have not been fully characterized. We measured several types of crosstalk in oocytes coexpressing α6β4 nAChRs and P2X2, P2X3, or P2X2/3 receptors. A novel form of crosstalk occurs between α6β4 nAChRs and P2X2 receptors. P2X2 receptors were forced into a prolonged desensitized state upon activation by ATP through a mechanism that does not depend on the intracellular C terminus of the P2X2 receptors. Coexpression of α6β4 nAChRs with P2X3 receptors shifts the ATP dose-response relation to the right, even in the absence of acetylcholine (ACh). Moreover, currents become nonadditive when ACh and ATP are coapplied, as previously reported for other Cys-loop receptors interacting with P2X receptors, and this crosstalk is dependent on the presence of the P2X3 C-terminal domain. P2X2 receptors also functionally interact with α6β4β3 but through a different mechanism from α6β4. The interaction with P2X3 receptors is less pronounced for the α6β4β3 nAChR than the α6β4 nAChR. We also measured a functional interaction between the α6β4 nAChRs and the heteromeric P2X2/3 receptor. Experiments with the nAChR channel blocker mecamylamine on P2X2-α6β4 oocytes point to the loss of P2X2 channel activity during the crosstalk, whereas the ion channel pores of the P2X receptors were fully functional and unaltered by the receptor interaction for P2X2-α6β4β3, P2X2/3-α6β4, and P2X2/3-α6β4β3. These results may be relevant to dorsal root ganglion cells and to other neurons that coexpress these receptor subunits.
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Affiliation(s)
- Walrati Limapichat
- Divisions of Chemistry and Chemical Engineering (W.L., D.A.D.) and Biology and Biological Engineering (H.A.L.), California Institute of Technology, Pasadena, California
| | - Dennis A Dougherty
- Divisions of Chemistry and Chemical Engineering (W.L., D.A.D.) and Biology and Biological Engineering (H.A.L.), California Institute of Technology, Pasadena, California
| | - Henry A Lester
- Divisions of Chemistry and Chemical Engineering (W.L., D.A.D.) and Biology and Biological Engineering (H.A.L.), California Institute of Technology, Pasadena, California
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Dash B, Li MD, Lukas RJ. Roles for N-terminal extracellular domains of nicotinic acetylcholine receptor (nAChR) β3 subunits in enhanced functional expression of mouse α6β2β3- and α6β4β3-nAChRs. J Biol Chem 2014; 289:28338-51. [PMID: 25028511 DOI: 10.1074/jbc.m114.566018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Functional heterologous expression of naturally expressed mouse α6*-nicotinic acetylcholine receptors (mα6*-nAChRs; where "*" indicates the presence of additional subunits) has been difficult. Here we expressed and characterized wild-type (WT), gain-of-function, chimeric, or gain-of-function chimeric nAChR subunits, sometimes as hybrid nAChRs containing both human (h) and mouse (m) subunits, in Xenopus oocytes. Hybrid mα6mβ4hβ3- (∼ 5-8-fold) or WT mα6mβ4mβ3-nAChRs (∼ 2-fold) yielded higher function than mα6mβ4-nAChRs. Function was not detected when mα6 and mβ2 subunits were expressed together or in the additional presence of hβ3 or mβ3 subunits. However, function emerged upon expression of mα6mβ2mβ3(V9'S)-nAChRs containing β3 subunits having gain-of-function V9'S (valine to serine at the 9'-position) mutations in transmembrane domain II and was further elevated 9-fold when hβ3(V9'S) subunits were substituted for mβ3(V9'S) subunits. Studies involving WT or gain-of-function chimeric mouse/human β3 subunits narrowed the search for domains that influence functional expression of mα6*-nAChRs. Using hβ3 subunits as templates for site-directed mutagenesis studies, substitution with mβ3 subunit residues in extracellular N-terminal domain loops "C" (Glu(221) and Phe(223)), "E" (Ser(144) and Ser(148)), and "β2-β3" (Gln(94) and Glu(101)) increased function of mα6mβ2*- (∼ 2-3-fold) or mα6mβ4* (∼ 2-4-fold)-nAChRs. EC50 values for nicotine acting at mα6mβ4*-nAChR were unaffected by β3 subunit residue substitutions in loop C or E. Thus, amino acid residues located in primary (loop C) or complementary (loops β2-β3 and E) interfaces of β3 subunits are some of the molecular impediments for functional expression of mα6mβ2β3- or mα6mβ4β3-nAChRs.
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Affiliation(s)
- Bhagirathi Dash
- From the Department of Psychiatry and Neurobehavioral Sciences, School of Medicine, University of Virginia, Charlottesville, Virginia 22911 and
| | - Ming D Li
- From the Department of Psychiatry and Neurobehavioral Sciences, School of Medicine, University of Virginia, Charlottesville, Virginia 22911 and
| | - Ronald J Lukas
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013
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Two rare variations, D478N and D478E, that occur at the same amino acid residue in nicotinic acetylcholine receptor (nAChR) α2 subunit influence nAChR function. Neuropharmacology 2014; 85:471-81. [PMID: 24950454 DOI: 10.1016/j.neuropharm.2014.05.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 05/09/2014] [Accepted: 05/12/2014] [Indexed: 11/22/2022]
Abstract
There occur two rare variations, Asp(D)478Asn(N) and Asp(D)478Glu(E), in the putative cytoplasmic amphipathic α-helices of human nicotinic acetylcholine receptor (nAChR) α2 subunit as a result of mutation in the 1st (G → A: rs141072985) and 3rd (C → A: rs56344740) nucleotide of its 478th triplet codon (GAC). We assessed the effects of these two variations on the function of α2β2- and α2β4-nAChRs as they could alter the electronegativity and/or the structure of the cytoplasmic 'portals' (framed by subunit amphipathic α-helices) necessary for obligate ion permeation from extracellular space to cytoplasm. We injected decreasing ratio of subunit cRNAs (α:β; 10:1, 1:1 and 1:10) into Xenopus oocytes to express putative low-sensitivity (LS; 10:1), intermediate-sensitivity (IS; 1:1) and high sensitivity (HS; 1:10) isoforms of wild type and variant α2β2- and α2β4-nAChRs. Two-electrode voltage clamp analyses indicate that the agonist (ACh or nicotine) induced peak current responses (Imax) of α2β2-nAChR isoforms and those of α2β4-nAChR isoforms are increased (1.3-4.7-fold) as a result of D478E variation. The α2 subunit D478N variation only increases the Imax of IS (∼2-fold) or HS (1.4-2.1-fold) α2β2-nAChRs. Concentration-response curves constructed indicate no effect on agonist sensitivities of LS and HS isoforms of α2β2- or α2β4-nAChRs as a result of either variation in α2 subunit. Between the two variant nAChRs, α2(D478E)*-nAChR isoforms generally yield higher Imax than those of respective α2(D478N)*-nAChR isoforms. These effects could be attributed to alteration in cytoplasmic 'portals' and/or ion permeation through it owing to change in amino acid electronegativity (D → N) and side chain length (D → E) in nAChR α2 subunit.
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Dash B, Li MD. Analysis of rare variations reveals roles of amino acid residues in the N-terminal extracellular domain of nicotinic acetylcholine receptor (nAChR) alpha6 subunit in the functional expression of human alpha6*-nAChRs. Mol Brain 2014; 7:35. [PMID: 24886653 PMCID: PMC4022547 DOI: 10.1186/1756-6606-7-35] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 04/22/2014] [Indexed: 12/17/2022] Open
Abstract
Background Functional heterologous expression of naturally-expressed and apparently functional mammalian α6*-nicotinic acetylcholine receptors (nAChRs; where ‘*’ indicates presence of additional subunits) has been difficult. Here we wanted to investigate the role of N-terminal domain (NTD) residues of human (h) nAChR α6 subunit in the functional expression of hα6*-nAChRs. To this end, instead of adopting random mutagenesis as a tool, we used 15 NTD rare variations (i.e., Ser43Pro, Asn46Lys, Asp57Asn, Arg87Cys, Asp92Glu, Arg96His, Glu101Lys, Ala112Val, Ser156Arg, Asn171Lys, Ala184Asp, Asp199Tyr, Asn203Thr, Ile226Thr and Ser233Cys) in nAChR hα6 subunit to probe for their effect on the functional expression of hα6*-nAChRs. Results N-terminal α-helix (Asp57); complementary face/inner β-fold (Arg87 or Asp92) and principal face/outer β-fold (Ser156 or Asn171) residues in the hα6 subunit are crucial for functional expression of the hα6*-nAChRs as variations in these residues reduce or abrogate the function of hα6hβ2*-, hα6hβ4- and hα6hβ4hβ3-nAChRs. While variations at residues Ser43 or Asn46 (both in N-terminal α-helix) in hα6 subunit reduce hα6hβ2*-nAChRs function those at residues Arg96 (β2-β3 loop), Asp199 (loop F) or Ser233 (β10-strand) increase hα6hβ2*-nAChR function. Similarly substitution of NTD α-helix (Asn46), loop F (Asp199), loop A (Ala112), loop B (Ala184), or loop C (Ile226) residues in hα6 subunit increase the function of hα6hβ4-nAChRs. All other variations in hα6 subunit do not affect the function of hα6hβ2*- and hα6hβ4*-nAChRs. Incorporation of nAChR hβ3 subunits always increase the function of wild-type or variant hα6hβ4-nAChRs except for those of hα6(D57N, S156R, R87C or N171K)hβ4-nAChRs. It appears Asp57Lys, Ser156Arg or Asn171Lys variations in hα6 subunit drive the hα6hβ4hβ3-nAChRs into a nonfunctional state as at spontaneously open hα6(D57N, S156R or N171K)hβ4hβ3V9’S-nAChRs (V9’S; transmembrane II 9’ valine-to-serine mutation) agonists act as antagonists. Agonist sensitivity of hα6hβ4- and/or hα6hβ4hβ3-nAChRs is nominally increased due to Arg96His, Ala184Asp, Asp199Tyr or Ser233Cys variation in hα6 subunit. Conclusions Hence investigating functional consequences of natural variations in nAChR hα6 subunit we have discovered additional bases for cell surface functional expression of various subtypes of hα6*-nAChRs. Variations (Asp57Asn, Arg87Cys, Asp92Glu, Ser156Arg or Asn171Lys) in hα6 subunit that compromise hα6*-nAChR function are expected to contribute to individual differences in responses to smoked nicotine.
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Affiliation(s)
| | - Ming D Li
- Department of Psychiatry and Neurobehavioral Sciences, School of Medicine, University of Virginia, Charlottesville, VA, USA.
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Feldstein Ewing SW, Karoly H, Hutchison KE. Commentary on Culverhouse et al. (2014): How genomics can bring us towards health equity. Addiction 2014; 109:823-4. [PMID: 24720827 PMCID: PMC4136635 DOI: 10.1111/add.12529] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Sarah W. Feldstein Ewing
- University of New Mexico, Department of Psychiatry, 1 University of New Mexico, MSC09 5030, Albuquerque, NM 87131 USA
| | - Hollis Karoly
- The University of Colorado at Boulder, Department of Psychology and Neuroscience, Muenzinger D244, 345 UCB, Boulder, CO 80309-0345 USA
| | - Kent E. Hutchison
- The University of Colorado at Boulder, Department of Psychology and Neuroscience, Muenzinger D244, 345 UCB, Boulder, CO 80309-0345 USA
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12
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Dash B, Lukas RJ, Li MD. A signal peptide missense mutation associated with nicotine dependence alters α2*-nicotinic acetylcholine receptor function. Neuropharmacology 2014; 79:715-25. [PMID: 24467848 DOI: 10.1016/j.neuropharm.2014.01.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 01/10/2014] [Accepted: 01/13/2014] [Indexed: 10/25/2022]
Abstract
A cytosine to thymidine (C → T) missense mutation in the signal peptide (SP) sequence (rs2472553) of the nicotinic acetylcholine receptor (nAChR) α2 subunit produces a threonine-to-isoleucine substitution (T22I) often associated with nicotine dependence (ND). We assessed effects on function of α2*-nAChR ('*'indicates presence of additional subunits) of this mutation, which could alter SP cleavage, RNA/protein secondary structure, and/or efficiency of transcription, translation, subunit assembly, receptor trafficking or cell surface expression. Two-electrode voltage clamp analyses indicate peak current responses to ACh or nicotine are decreased 2.8-5.8-fold for putative low sensitivity (LS; 10:1 ratio of α:β subunit cRNAs injected) α2β2- or α2β4-nAChR and increased for putative high sensitivity (HS; 1:10 α:β subunit ratio) α2β2- (5.7-15-fold) or α2β4- (1.9-2.2-fold) nAChR as a result of the mutation. Agonist potencies are decreased 1.6-4-fold for putative LS or HS α2(T22I)β2-nAChR or for either α2*-nAChR subtype formed in the presence of equal amounts of subunit cRNA, slightly decreased for LS α2(T22I)β4-nAChR, but increased 1.4-2.4-fold for HS α2(T22I)β4-nAChR relative to receptors containing wild-type α2 subunits. These effects suggest that the α2 subunit SP mutation generally favors formation of LS receptor isoforms. We hypothesize that lower sensitivity of human α2*-nAChR to nicotine could contribute to increased susceptibility to ND. To our knowledge this is the first report of a SP mutation having a functional effect in a member of cys-loop family of ligand-gated ion channels.
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Affiliation(s)
- Bhagirathi Dash
- Department of Psychiatry and Neurobehavioral Sciences, School of Medicine, University of Virginia, Charlottesville, VA 22911, USA
| | - Ronald J Lukas
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, AZ 85013, USA
| | - Ming D Li
- Department of Psychiatry and Neurobehavioral Sciences, School of Medicine, University of Virginia, Charlottesville, VA 22911, USA.
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Biophysical and pharmacological characterization of α6-containing nicotinic acetylcholine receptors expressed in HEK293 cells. Brain Res 2013; 1542:1-11. [PMID: 24157862 DOI: 10.1016/j.brainres.2013.10.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2013] [Revised: 09/16/2013] [Accepted: 10/14/2013] [Indexed: 11/23/2022]
Abstract
Nicotinic acetylcholine receptors (nAChR's) containing the α6 subunit (α6) are putative drug targets of relevance to Parkinson's disease and nicotine addiction. However, heterologous expression of α6 receptors has proven challenging which has stifled drug discovery efforts. Here, we investigate potential new avenues for achieving functional α6 receptor expression. Combinations of chimeric and mutated α6, β2 and β3 subunits were co-expressed in the human HEK293 cell line and receptor expression was assessed using Ca(2+)-imaging (FLIPR™) and whole-cell patch-clamp electrophysiology. Transient transfections of a chimeric α6/α3 subunit construct in combination with β2 and β3(V9'S) gave rise to significant acetylcholine-evoked whole-cell currents. Increasing the β3(V9'S):β2:α6/α3 cDNA ratio, resulted in a significantly higher fraction of cells with robust current levels. Using an excess of wild-type β3, significant functional expression of α6/α3β2β3 was also demonstrated. Comparing the acetylcholine concentration-response relationship of α6/α3β2β3(V9'S) to that of α6/α3β2β3 revealed the β3 point mutation to result in decreased current decay rate and increased ACh agonist potency. Ca(2+)-imaging experiments showed preservation of basic α6 receptor pharmacology. Our results establish that α6/α3β2β3(V9'S) replicate several basic features of native α6 receptors but also highlight several caveats associated with using this construct and may therefore provide guidance for future drug hunting efforts.
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Abu-Amero KK, Kondkar A, Hellani AM, Oystreck DT, Khan AO, Bosley TM. Nicotinic Receptor Mutation in a Mildly Dysmorphic Girl with Duane Retraction Syndrome. Ophthalmic Genet 2013; 36:99-104. [DOI: 10.3109/13816810.2013.835431] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Khaled K Abu-Amero
- Department of Ophthalmology, College of Medicine, King Saud University , Riyadh , Saudi Arabia
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