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Choi SH, Byambaragchaa M, Kim DJ, Lee JH, Kang MH, Min KS. Specific Signal Transduction of Constitutively Activating (D576G) and Inactivating (R476H) Mutants of Agonist-Stimulated Luteinizing Hormone Receptor in Eel. Int J Mol Sci 2023; 24:ijms24119133. [PMID: 37298083 DOI: 10.3390/ijms24119133] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 05/02/2023] [Accepted: 05/20/2023] [Indexed: 06/12/2023] Open
Abstract
We investigated the mechanism of signal transduction using inactivating (R476H) and activating (D576G) mutants of luteinizing hormone receptor (LHR) of eel at the conserved regions of intracellular loops II and III, respectively, naturally occurring in mammalian LHR. The expression of D576G and R476H mutants was approximately 58% and 59%, respectively, on the cell surface compared to those of eel LHR-wild type (wt). In eel LHR-wt, cAMP production increased upon agonist stimulation. Cells expressing eel LHR-D576G, a highly conserved aspartic acid residue, exhibited a 5.8-fold increase in basal cAMP response; however, the maximal cAMP response by high-agonist stimulation was approximately 0.62-fold. Mutation of a highly conserved arginine residue in the second intracellular loop of eel LHR (LHR-R476H) completely impaired the cAMP response. The rate of loss in cell-surface expression of eel LHR-wt and D576G mutant was similar to the agonist recombinant (rec)-eel LH after 30 min. However, the mutants presented rates of loss higher than eel LHR-wt did upon rec-eCG treatment. Therefore, the activating mutant constitutively induced cAMP signaling. The inactivating mutation resulted in the loss of LHR expression on the cell surface and no cAMP signaling. These data provide valuable information regarding the structure-function relationship of LHR-LH complexes.
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Affiliation(s)
- Seung-Hee Choi
- Animal BioScience, School of Animal Life Convergence, Hankyong National University, Ansung 17579, Republic of Korea
| | - Munkhzaya Byambaragchaa
- Institute of Genetic Engineering, Hankyong National University, Ansung 17579, Republic of Korea
| | - Dae-Jung Kim
- Aquaculture Industry Division, South Sea Fisheries Research Institute, National Institute of Fisheries Science (NIFS), Yeosu 59780, Republic of Korea
| | - Jong-Hyuk Lee
- College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Myung-Hwa Kang
- Department of Food Science and Nutrition, Hoseo University, Asan 31499, Republic of Korea
| | - Kwan-Sik Min
- Animal BioScience, School of Animal Life Convergence, Hankyong National University, Ansung 17579, Republic of Korea
- Institute of Genetic Engineering, Hankyong National University, Ansung 17579, Republic of Korea
- Carbon-Neutral Resources Research Center, Hankyong National University, Ansung 17579, Republic of Korea
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Byambaragchaa M, Seong HK, Choi SH, Kim DJ, Kang MH, Min KS. Constitutively Activating Mutants of Equine LH/CGR Constitutively Induce Signal Transduction and Inactivating Mutations Impair Biological Activity and Cell-Surface Receptor Loss In Vitro. Int J Mol Sci 2021; 22:ijms221910723. [PMID: 34639064 PMCID: PMC8509413 DOI: 10.3390/ijms221910723] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 09/30/2021] [Accepted: 10/01/2021] [Indexed: 12/26/2022] Open
Abstract
The signal transduction of the equine lutropin/choriogonadotropin receptor (eLH/CGR) is unclear in naturally occurring activating/inactivating mutants of this receptor, which plays an important role in reproductive physiology. We undertook the present study to determine whether conserved structurally related mutations in eLH/CGR exhibit similar mechanisms of signal transduction. We constructed four constitutively activating mutants (M398T, L457R, D564G, and D578Y) and three inactivating mutants (D405N, R464H, and Y546F); measured cyclic adenosine monophosphate (cAMP) accumulation via homogeneous time-resolved fluorescence assays in Chinese hamster ovary cells; and investigated cell-surface receptor loss using an enzyme-linked immunosorbent assay in human embryonic kidney 293 cells. The eLH/CGR-L457R-, -D564G-, and -D578Y-expressing cells exhibited 16.9-, 16.4-, and 11.2-fold increases in basal cAMP response, respectively. The eLH/CGR-D405N- and R464H-expressing cells presented a completely impaired signal transduction, whereas the Y546F-expressing cells exhibited a small increase in cAMP response. The cell-surface receptor loss was 1.4- to 2.4-fold greater in the activating-mutant-expressing cells than in wild-type eLH/CGR-expressing cells, but was completely impaired in the D405N- and Y546F-expressing cells, despite treatment with a high concentration of agonist. In summary, the state of activation of eLH/CGR influenced agonist-induced cell-surface receptor loss, which was directly related to the signal transduction of constitutively activating mutants.
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Affiliation(s)
- Munkhzaya Byambaragchaa
- Institute of Genetic Engineering, Hankyong National University, Ansung 17579, Korea; (M.B.); (H.-K.S.)
| | - Hoon-Ki Seong
- Institute of Genetic Engineering, Hankyong National University, Ansung 17579, Korea; (M.B.); (H.-K.S.)
| | - Seung-Hee Choi
- Animal Biotechnology, Graduate School of Future Convergence Technology, Hankyong National University, Ansung 17579, Korea;
| | - Dae-Jung Kim
- Jeju Fisheries Research Institute, National Institute of Fisheries Science (NIFS), Jeju 63610, Korea;
| | - Myung-Hwa Kang
- Department of Food Science and Nutrition, Hoseo University, Asan 31499, Korea;
| | - Kwan-Sik Min
- Institute of Genetic Engineering, Hankyong National University, Ansung 17579, Korea; (M.B.); (H.-K.S.)
- Animal Biotechnology, Graduate School of Future Convergence Technology, Hankyong National University, Ansung 17579, Korea;
- Correspondence: ; Tel.: +82-31-670-5421; Fax: +82-31-670-5417
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Byambaragchaa M, Kim JS, Park HK, Kim DJ, Hong SM, Kang MH, Min KS. Constitutive Activation and Inactivation of Mutations Inducing Cell Surface Loss of Receptor and Impairing of Signal Transduction of Agonist-Stimulated Eel Follicle-Stimulating Hormone Receptor. Int J Mol Sci 2020; 21:E7075. [PMID: 32992880 DOI: 10.3390/ijms21197075] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Revised: 09/23/2020] [Accepted: 09/23/2020] [Indexed: 12/17/2022] Open
Abstract
In the present study, we investigated the signal transduction of mutants of the eel follicle-stimulating hormone receptor (eelFSHR). Specifically, we examined the constitutively activating mutant D540G in the third intracellular loop, and four inactivating mutants (A193V, N195I, R546C, and A548V). To directly assess functional effects, we conducted site-directed mutagenesis to generate mutant receptors. We measured cyclic adenosine monophosphate (cAMP) accumulation via homogeneous time-resolved fluorescence assays in Chinese hamster ovary (CHO-K1) cells and investigated cell surface receptor loss using an enzyme-linked immunosorbent assay in human embryonic kidney (HEK) 293 cells. The cells expressing eelFSHR-D540G exhibited a 23-fold increase in the basal cAMP response without agonist treatment. The cells expressing A193V, N195I, and A548V mutants had completely impaired signal transduction, whereas those expressing the R546C mutant exhibited little increase in cAMP responsiveness and a small increase in signal transduction. Cell surface receptor loss in the cells expressing inactivating mutants A193V, R546C, and A548V was clearly slower than in the cell expressing the wild-type eelFSHR. However, cell surface receptor loss in the cells expressing inactivating mutant N195I decreased in a similar manner to that of the cells expressing the wild-type eelFSHR or the activating mutant D540G, despite the completely impaired cAMP response. These results provide important information regarding the structure–function relationships of G protein-coupled receptors during signal transduction.
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Dong J, Subbotina E, Williams N, Sampson BA, Tang Y, Coetzee WA. Functional reclassification of variants of uncertain significance in the HCN4 gene identified in sudden unexpected death. Pacing Clin Electrophysiol 2019; 42:275-282. [PMID: 30578647 DOI: 10.1111/pace.13593] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [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: 09/21/2018] [Revised: 12/07/2018] [Accepted: 12/18/2018] [Indexed: 11/28/2022]
Abstract
The HCN4 gene encodes a subunit of the hyperpolarization-activated cyclic nucleotide-gated channel, type 4 that is essential for the proper generation of pacemaker potentials in the sinoatrial node. The HCN4 gene is often present in targeted genetic testing panels for various cardiac conduction system disorders and there are several reports of HCN4 variants associated with conduction disorders. Here, we report the in vitro functional characterization of four rare variants of uncertain significance (VUS) in HCN4, identified through testing a cohort of 296 sudden unexpected natural deaths. The variants are all missense alterations, leading to single amino acid changes: p.E66Q in the N-terminus, p.D546N in the C-linker domain, and both p.S935Y and p.R1044Q in the C-terminus distal to the CNBD. We also identified a likely benign variant, p. P1063T, which has a high minor allele frequency in the gnomAD, which is utilized here as a negative control. Three of the HCN4 VUS (p.E66Q, p.S935Y, and p.R1044Q) had electrophysiological characteristics similar to the wild-type channel, suggesting that these variants are benign. In contrast, the p.D546N variant in the C-linker domain exhibited a larger current density, slower activation, and was unresponsive to cyclic adenosine monophosphate (cAMP) compared to wild-type. With functional assays, we reclassified three rare HCN4 VUS to likely benign variants, eliminating the necessity for costly and time-consuming further study. Our studies also provide a new lead to investigate how a VUS located in the C-linker connecting the pore to the cAMP binding domain may affect the channel open state probability and cAMP response.
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Affiliation(s)
- Jingyun Dong
- Departments of Pediatrics, NYU School of Medicine, New York, New York
| | | | - Nori Williams
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, New York, New York
| | - Barbara A Sampson
- Department of Forensic Pathology, New York City Office of Chief Medical Examiner, New York, New York
| | - Yingying Tang
- Molecular Genetics Laboratory, New York City Office of Chief Medical Examiner, New York, New York
| | - William A Coetzee
- Departments of Pediatrics, NYU School of Medicine, New York, New York.,Departments of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York.,Departments of Physiology and Neurosciences, NYU School of Medicine, New York, New York
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Lee HJ, Son Y, Lee M, Moon C, Kim SH, Shin IS, Yang M, Bae S, Kim JS. Sodium butyrate prevents radiation-induced cognitive impairment by restoring pCREB/BDNF expression. Neural Regen Res 2019; 14:1530-1535. [PMID: 31089051 PMCID: PMC6557090 DOI: 10.4103/1673-5374.255974] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Sodium butyrate is a histone deacetylase inhibitor that affects various types of brain damages. To investigate the effects of sodium butyrate on hippocampal dysfunction that occurs after whole-brain irradiation in animal models and the effect of sodium butyrate on radiation exposure-induced cognitive impairments, adult C57BL/6 mice were intraperitoneally treated with 0.6 g/kg sodium butyrate before exposure to 10 Gy cranial irradiation. Cognitive impairment in adult C57BL/6 mice was evaluated via an object recognition test 30 days after irradiation. We also detected the expression levels of neurogenic cell markers (doublecortin) and phosphorylated cAMP response element binding protein/brain-derived neurotrophic factor. Radiation-exposed mice had decreased cognitive function and hippocampal doublecortin and phosphorylated cAMP response element binding protein/brain-derived neurotrophic factor expression. Sodium butyrate pretreatment reversed these changes. These findings suggest that sodium butyrate can improve radiation-induced cognitive dysfunction through inhibiting the decrease in hippocampal phosphorylated cAMP response element binding protein/brain-derived neurotrophic factor expression. The study procedures were approved by the Institutional Animal Care and Use Committee of Korea Institute of Radiological Medical Sciences (approval No. KIRAMS16-0002) on December 30, 2016.
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Affiliation(s)
- Hae June Lee
- Division of Basic Radiation Bioscience, Korea Institute of Radiological & Medical Sciences (KIRMAS), Seoul, Republic of Korea
| | - Yeonghoon Son
- Division of Basic Radiation Bioscience, Korea Institute of Radiological & Medical Sciences (KIRMAS), Seoul; National Primate Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Cheongju, Republic of Korea
| | - Minyoung Lee
- College of Pharmacy, Kyungpook National University, Daegu, Republic of Korea
| | - Changjong Moon
- College of Veterinary Medicine, Veterinary Medical Research Institute, Chonnam National University, Gwangju, Republic of Korea
| | - Sung Ho Kim
- College of Veterinary Medicine, Veterinary Medical Research Institute, Chonnam National University, Gwangju, Republic of Korea
| | - In Sik Shin
- College of Veterinary Medicine, Veterinary Medical Research Institute, Chonnam National University, Gwangju, Republic of Korea
| | - Miyoung Yang
- School of Medicine, Wonkwang University, Jeonbuk, Republic of Korea
| | - Sangwoo Bae
- Division of Basic Radiation Bioscience, Korea Institute of Radiological & Medical Sciences (KIRMAS), Seoul, Republic of Korea
| | - Joong Sun Kim
- Research Center, Dongnam Institute of Radiological & Medical Sciences (DIRAMS), Busan, Republic of Korea
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