1
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Mehrabipour M, Nakhaei-Rad S, Dvorsky R, Lang A, Verhülsdonk P, Ahmadian MR, Piekorz RP. SIRT4 as a novel interactor and candidate suppressor of C-RAF kinase in MAPK signaling. Life Sci Alliance 2024; 7:e202302507. [PMID: 38499327 PMCID: PMC10948936 DOI: 10.26508/lsa.202302507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 03/06/2024] [Accepted: 03/07/2024] [Indexed: 03/20/2024] Open
Abstract
Cellular responses leading to development, proliferation, and differentiation depend on RAF/MEK/ERK signaling, which integrates and amplifies signals from various stimuli for downstream cellular responses. C-RAF activation has been reported in many types of tumor cell proliferation and developmental disorders, necessitating the discovery of potential C-RAF protein regulators. Here, we identify a novel and specific protein interaction between C-RAF among the RAF kinase paralogs, and SIRT4 among the mitochondrial sirtuin family members SIRT3, SIRT4, and SIRT5. Structurally, C-RAF binds to SIRT4 through the N-terminal cysteine-rich domain, whereas SIRT4 predominantly requires the C-terminus for full interaction with C-RAF. Interestingly, SIRT4 specifically interacts with C-RAF in a pre-signaling inactive (serine 259-phosphorylated) state. Consistent with this finding, the expression of SIRT4 in HEK293 cells results in an up-regulation of pS259-C-RAF levels and a concomitant reduction in MAPK signaling as evidenced by strongly decreased phospho-ERK signals. Thus, we propose an additional extra-mitochondrial function of SIRT4 as a cytosolic tumor suppressor of C-RAF-MAPK signaling, besides its metabolic tumor suppressor role of glutamate dehydrogenase and glutamate levels in mitochondria.
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Affiliation(s)
- Mehrnaz Mehrabipour
- Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - Saeideh Nakhaei-Rad
- Stem Cell Biology, and Regenerative Medicine Research Group, Institute of Biotechnology, Ferdowsi University of Mashhad, Mashhad, Iran
| | - Radovan Dvorsky
- Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - Alexander Lang
- Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - Patrick Verhülsdonk
- Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - Mohammad R Ahmadian
- Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - Roland P Piekorz
- Institute of Biochemistry and Molecular Biology II, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
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2
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Hsieh CH, Chou CC, Fang YC, Hsu PH, Chiu YH, Yang CS, Jow GM, Tang CY, Jeng CJ. 14-3-3 proteins regulate cullin 7-mediated Eag1 degradation. Cell Biosci 2023; 13:18. [PMID: 36717938 PMCID: PMC9885684 DOI: 10.1186/s13578-023-00969-w] [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: 10/25/2022] [Accepted: 01/23/2023] [Indexed: 01/31/2023] Open
Abstract
BACKGROUND Mutations in the human gene encoding the neuron-specific Eag1 (KV10.1; KCNH1) potassium channel are linked to congenital neurodevelopmental diseases. Disease-causing mutant Eag1 channels manifest aberrant gating function and defective protein homeostasis. Both the E3 ubiquitin ligase cullin 7 (Cul7) and the small acid protein 14-3-3 serve as binding partners of Eag1. Cul7 mediates proteasomal and lysosomal degradation of Eag1 protein, whereas over-expression of 14-3-3 notably reduces Eag1 channel activity. It remains unclear whether 14-3-3 may also contribute to Eag1 protein homeostasis. RESULTS In human cell line and native rat neurons, disruptions of endogenous 14-3-3 function with the peptide inhibitor difopein or specific RNA interference up-regulated Eag1 protein level in a transcription-independent manner. Difopein hindered Eag1 protein ubiquitination at the endoplasmic reticulum and the plasma membrane, effectively promoting the stability of both immature and mature Eag1 proteins. Suppression of endogenous 14-3-3 function also reduced excitotoxicity-associated Eag1 degradation in neurons. Difopein diminished Cul7-mediated Eag1 degradation, and Cul7 knock-down abolished the effect of difopein on Eag1. Inhibition of endogenous 14-3-3 function substantially perturbed the interaction of Eag1 with Cul7. Further structural analyses suggested that the intracellular Per-Arnt-Sim (PAS) domain and cyclic nucleotide-binding homology domain (CNBHD) of Eag1 are essential for the regulatory effect of 14-3-3 proteins. Significantly, suppression of endogenous 14-3-3 function reduced Cul7-mediated degradation of disease-associated Eag1 mutant proteins. CONCLUSION Overall these results highlight a chaperone-like role of endogenous 14-3-3 proteins in regulating Eag1 protein homeostasis, as well as a therapeutic potential of 14-3-3 modulators in correcting defective protein expression of disease-causing Eag1 mutants.
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Affiliation(s)
- Chang-Heng Hsieh
- grid.260539.b0000 0001 2059 7017Institute of Anatomy and Cell Biology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, 112 Taiwan
| | - Chia-Cheng Chou
- grid.36020.370000 0000 8889 3720National Laboratory Animal Center, National Applied Research Laboratories, Taipei, Taiwan
| | - Ya-Ching Fang
- grid.260539.b0000 0001 2059 7017Institute of Anatomy and Cell Biology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, 112 Taiwan ,grid.19188.390000 0004 0546 0241Department of Physiology, College of Medicine, National Taiwan University, Taipei, 100 Taiwan
| | - Po-Hao Hsu
- grid.260539.b0000 0001 2059 7017Institute of Anatomy and Cell Biology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, 112 Taiwan ,grid.19188.390000 0004 0546 0241Department of Physiology, College of Medicine, National Taiwan University, Taipei, 100 Taiwan
| | - Yi-Hung Chiu
- grid.260539.b0000 0001 2059 7017Institute of Anatomy and Cell Biology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, 112 Taiwan
| | - Chi-Sheng Yang
- grid.260539.b0000 0001 2059 7017Institute of Anatomy and Cell Biology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, 112 Taiwan
| | - Guey-Mei Jow
- grid.256105.50000 0004 1937 1063School of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan
| | - Chih-Yung Tang
- grid.19188.390000 0004 0546 0241Department of Physiology, College of Medicine, National Taiwan University, Taipei, 100 Taiwan
| | - Chung-Jiuan Jeng
- grid.260539.b0000 0001 2059 7017Institute of Anatomy and Cell Biology, College of Medicine, National Yang Ming Chiao Tung University, Taipei, 112 Taiwan ,grid.260539.b0000 0001 2059 7017Brain Research Center, National Yang Ming Chiao Tung University, Taipei, Taiwan
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Lankford C, Houtman J, Baker SA. Identification of HCN1 as a 14-3-3 client. PLoS One 2022; 17:e0268335. [PMID: 35679272 PMCID: PMC9182292 DOI: 10.1371/journal.pone.0268335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 04/28/2022] [Indexed: 11/19/2022] Open
Abstract
Hyperpolarization activated cyclic nucleotide-gated channel 1 (HCN1) is expressed throughout the nervous system and is critical for regulating neuronal excitability, with mutations being associated with multiple forms of epilepsy. Adaptive modulation of HCN1 has been observed, as has pathogenic dysregulation. While the mechanisms underlying this modulation remain incompletely understood, regulation of HCN1 has been shown to include phosphorylation. A candidate phosphorylation-dependent regulator of HCN1 channels is 14-3-3. We used bioinformatics to identify three potential 14-3-3 binding sites in HCN1. We confirmed that 14-3-3 could pull down HCN1 from multiple tissue sources and used HEK293 cells to detail the interaction. Two sites in the intrinsically disordered C-terminus of HCN1 were necessary and sufficient for a phosphorylation-dependent interaction with 14-3-3. The same region of HCN1 containing the 14-3-3 binding peptides is required for phosphorylation-independent protein degradation. We propose a model in which phosphorylation of mouse S810 and S867 (human S789 and S846) recruits 14-3-3 to inhibit a yet unidentified factor signaling for protein degradation, thus increasing the half-life of HCN1.
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Affiliation(s)
- Colten Lankford
- Department of Biochemistry and Molecular Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Jon Houtman
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa, United States of America
| | - Sheila A. Baker
- Department of Biochemistry and Molecular Biology, University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
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4
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Toplak Ž, Hendrickx LA, Abdelaziz R, Shi X, Peigneur S, Tomašič T, Tytgat J, Peterlin-Mašič L, Pardo LA. Overcoming challenges of HERG potassium channel liability through rational design: Eag1 inhibitors for cancer treatment. Med Res Rev 2021; 42:183-226. [PMID: 33945158 DOI: 10.1002/med.21808] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 02/18/2021] [Accepted: 03/31/2021] [Indexed: 12/11/2022]
Abstract
Two decades of research have proven the relevance of ion channel expression for tumor progression in virtually every indication, and it has become clear that inhibition of specific ion channels will eventually become part of the oncology therapeutic arsenal. However, ion channels play relevant roles in all aspects of physiology, and specificity for the tumor tissue remains a challenge to avoid undesired effects. Eag1 (KV 10.1) is a voltage-gated potassium channel whose expression is very restricted in healthy tissues outside of the brain, while it is overexpressed in 70% of human tumors. Inhibition of Eag1 reduces tumor growth, but the search for potent inhibitors for tumor therapy suffers from the structural similarities with the cardiac HERG channel, a major off-target. Existing inhibitors show low specificity between the two channels, and screenings for Eag1 binders are prone to enrichment in compounds that also bind HERG. Rational drug design requires knowledge of the structure of the target and the understanding of structure-function relationships. Recent studies have shown subtle structural differences between Eag1 and HERG channels with profound functional impact. Thus, although both targets' structure is likely too similar to identify leads that exclusively bind to one of the channels, the structural information combined with the new knowledge of the functional relevance of particular residues or areas suggests the possibility of selective targeting of Eag1 in cancer therapies. Further development of selective Eag1 inhibitors can lead to first-in-class compounds for the treatment of different cancers.
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Affiliation(s)
- Žan Toplak
- Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
| | - Louise A Hendrickx
- Department of Toxicology and Pharmacology, University of Leuven, Leuven, Belgium
| | - Reham Abdelaziz
- AG Oncophysiology, Max-Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Xiaoyi Shi
- AG Oncophysiology, Max-Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Steve Peigneur
- Department of Toxicology and Pharmacology, University of Leuven, Leuven, Belgium
| | - Tihomir Tomašič
- Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
| | - Jan Tytgat
- Department of Toxicology and Pharmacology, University of Leuven, Leuven, Belgium
| | | | - Luis A Pardo
- AG Oncophysiology, Max-Planck Institute for Experimental Medicine, Göttingen, Germany
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5
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Chen S, Feng X, Chen X, Zhuang Z, Xiao J, Fu H, Klein JD, Wang XH, Hoover RS, Eaton DC, Cai H. 14-3-3γ, a novel regulator of the large-conductance Ca 2+-activated K + channel. Am J Physiol Renal Physiol 2020; 319:F52-F62. [PMID: 32463725 DOI: 10.1152/ajprenal.00584.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
14-3-3γ is a small protein regulating its target proteins through binding to phosphorylated serine/threonine residues. Sequence analysis of large-conductance Ca2+-activated K+ (BK) channels revealed a putative 14-3-3 binding site in the COOH-terminal region. Our previous data showed that 14-3-3γ is widely expressed in the mouse kidney. Therefore, we hypothesized that 14-3-3γ has a novel role in the regulation of BK channel activity and protein expression. We used electrophysiology, Western blot analysis, and coimmunoprecipitation to examine the effects of 14-3-3γ on BK channels both in vitro and in vivo. We demonstrated the interaction of 14-3-3γ with BK α-subunits (BKα) by coimmunoprecipitation. In human embryonic kidney-293 cells stably expressing BKα, overexpression of 14-3-3γ significantly decreased BK channel activity and channel open probability. 14-3-3γ inhibited both total and cell surface BKα protein expression while enhancing ERK1/2 phosphorylation in Cos-7 cells cotransfected with flag-14-3-3γ and myc-BK. Knockdown of 14-3-3γ by siRNA transfection markedly increased BKα expression. Blockade of the ERK1/2 pathway by incubation with the MEK-specific inhibitor U0126 partially abolished 14-3-3γ-mediated inhibition of BK protein expression. Similarly, pretreatment of the lysosomal inhibitor bafilomycin A1 reversed the inhibitory effects of 14-3-3γ on BK protein expression. Furthermore, overexpression of 14-3-3γ significantly increased BK protein ubiquitination in embryonic kidney-293 cells stably expressing BKα. Additionally, 3 days of dietary K+ challenge reduced 14-3-3γ expression and ERK1/2 phosphorylation while enhancing renal BK protein expression and K+ excretion. These data suggest that 14-3-3γ modulates BK channel activity and protein expression through an ERK1/2-mediated ubiquitin-lysosomal pathway.
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Affiliation(s)
- Shan Chen
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiuyan Feng
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Department of Pathology and Translational Pathobiology, Louisiana State University Health Sciences Center, Shreveport, Louisiana
| | - Xinxin Chen
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Zhizhi Zhuang
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Jia Xiao
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Haian Fu
- Department of Pharmacology, Emory University, School of Medicine, Atlanta, Georgia
| | - Janet D Klein
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Xiaonan H Wang
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Robert S Hoover
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Section of Nephrology, Atlanta Veterans Administration Medical Center, Decatur, Georgia.,Physiology, Emory University, School of Medicine, Atlanta, Georgia
| | - Douglas C Eaton
- Physiology, Emory University, School of Medicine, Atlanta, Georgia
| | - Hui Cai
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Section of Nephrology, Atlanta Veterans Administration Medical Center, Decatur, Georgia.,Physiology, Emory University, School of Medicine, Atlanta, Georgia
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6
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Cázares-Ordoñez V, Pardo L. Kv10.1 potassium channel: from the brain to the tumors. Biochem Cell Biol 2017; 95:531-536. [DOI: 10.1139/bcb-2017-0062] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The KCNH1 gene encodes the Kv10.1 (Eag1) ion channel, a member of the EAG (ether-à-go-go) family of voltage-gated potassium channels. Recent studies have demonstrated that KCHN1 mutations are implicated in Temple–Baraitser and Zimmermann–Laband syndromes and other forms of developmental deficits that all present with mental retardation and epilepsy, suggesting that Kv10.1 might be important for cognitive development in humans. Although the Kv10.1 channel is mainly expressed in the mammalian brain, its ectopic expression occurs in 70% of human cancers. Cancer cells and tumors expressing Kv10.1 acquire selective advantages that favor cancer progression through molecular mechanisms that involve several cellular pathways, indicating that protein–protein interactions may be important for Kv10.1 influence in cell proliferation and tumorigenesis. Several studies on transcriptional and post-transcriptional regulation of Kv10.1 expression have shown interesting mechanistic insights about Kv10.1 role in oncogenesis, increasing the importance of identifying the cellular factors that regulate Kv10.1 expression in tumors.
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Affiliation(s)
- V. Cázares-Ordoñez
- Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
- Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
| | - L.A. Pardo
- Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
- Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
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7
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Eag1 K + Channel: Endogenous Regulation and Functions in Nervous System. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:7371010. [PMID: 28367272 PMCID: PMC5358448 DOI: 10.1155/2017/7371010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 12/27/2016] [Accepted: 01/31/2017] [Indexed: 02/04/2023]
Abstract
Ether-à-go-go1 (Eag1, Kv10.1, KCNH1) K+ channel is a member of the voltage-gated K+ channel family mainly distributed in the central nervous system and cancer cells. Like other types of voltage-gated K+ channels, the EAG1 channels are regulated by a variety of endogenous signals including reactive oxygen species, rendering the EAG1 to be in the redox-regulated ion channel family. The role of EAG1 channels in tumor development and its therapeutic significance have been well established. Meanwhile, the importance of hEAG1 channels in the nervous system is now increasingly appreciated. The present review will focus on the recent progress on the channel regulation by endogenous signals and the potential functions of EAG1 channels in normal neuronal signaling as well as neurological diseases.
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8
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Whicher JR, MacKinnon R. Structure of the voltage-gated K⁺ channel Eag1 reveals an alternative voltage sensing mechanism. Science 2016; 353:664-9. [PMID: 27516594 DOI: 10.1126/science.aaf8070] [Citation(s) in RCA: 234] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 06/22/2016] [Indexed: 12/17/2022]
Abstract
Voltage-gated potassium (K(v)) channels are gated by the movement of the transmembrane voltage sensor, which is coupled, through the helical S4-S5 linker, to the potassium pore. We determined the single-particle cryo-electron microscopy structure of mammalian K(v)10.1, or Eag1, bound to the channel inhibitor calmodulin, at 3.78 angstrom resolution. Unlike previous K(v) structures, the S4-S5 linker of Eag1 is a five-residue loop and the transmembrane segments are not domain swapped, which suggest an alternative mechanism of voltage-dependent gating. Additionally, the structure and position of the S4-S5 linker allow calmodulin to bind to the intracellular domains and to close the potassium pore, independent of voltage-sensor position. The structure reveals an alternative gating mechanism for K(v) channels and provides a template to further understand the gating properties of Eag1 and related channels.
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Affiliation(s)
- Jonathan R Whicher
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA.
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9
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Hsu PH, Chiu YC, Lin TF, Jeng CJ. Ca(2+)-binding protein centrin 4 is a novel binding partner of rat Eag1 K(+) channels. FEBS Open Bio 2016; 6:349-57. [PMID: 27239447 PMCID: PMC4821352 DOI: 10.1002/2211-5463.12045] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 02/14/2016] [Accepted: 02/16/2016] [Indexed: 01/14/2023] Open
Abstract
Eag1 is neuron-specific K(+) channel abundantly expressed in the brain and retina. Subcellular localization and physiological analyses in neurons reveal that Eag1 may participate in Ca(2+)-signaling processes in the synapse. Here, we searched for rat Eag1 (rEag1)-binding proteins that may contribute to Ca(2+) regulation of the K(+) channel. Yeast two-hybrid screening identified centrin 4, a member of the centrin family of Ca(2+)-binding proteins. GST pull-down and immunoprecipitation assays in brain and retina lysates confirm the interaction of centrin with rEag1 in neurons. Centrin 4 binds to rEag1 in the absence of Ca(2+). Raising Ca(2+) concentration enhances the association efficiency of centrin 4 and rEag1, and is required for the suppression of rEag1 currents by centrin 4. Altogether, our data suggest that centrin 4 is a novel binding partner that may contribute to Ca(2+) regulation of rEag1 in neurons.
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Affiliation(s)
- Po-Hao Hsu
- Institute of Anatomy and Cell Biology School of Medicine National Yang-Ming University Taipei Taiwan
| | - Yi-Chih Chiu
- Institute of Anatomy and Cell Biology School of Medicine National Yang-Ming University Taipei Taiwan
| | - Ting-Feng Lin
- Institute of Anatomy and Cell Biology School of Medicine National Yang-Ming University Taipei Taiwan
| | - Chung-Jiuan Jeng
- Institute of Anatomy and Cell Biology School of Medicine National Yang-Ming University Taipei Taiwan; Brain Research Center National Yang-Ming University Taipei Taiwan
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10
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Kv10.1 K+ channel: from physiology to cancer. Pflugers Arch 2016; 468:751-62. [DOI: 10.1007/s00424-015-1784-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 12/11/2015] [Accepted: 12/27/2015] [Indexed: 12/18/2022]
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11
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Ramos Gomes F, Romaniello V, Sánchez A, Weber C, Narayanan P, Psol M, Pardo LA. Alternatively Spliced Isoforms of KV10.1 Potassium Channels Modulate Channel Properties and Can Activate Cyclin-dependent Kinase in Xenopus Oocytes. J Biol Chem 2015; 290:30351-65. [PMID: 26518875 PMCID: PMC4683259 DOI: 10.1074/jbc.m115.668749] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Indexed: 12/18/2022] Open
Abstract
KV10.1 is a voltage-gated potassium channel expressed selectively in the mammalian brain but also aberrantly in cancer cells. In this study we identified short splice variants of KV10.1 resulting from exon-skipping events (E65 and E70) in human brain and cancer cell lines. The presence of the variants was confirmed by Northern blot and RNase protection assays. Both variants completely lacked the transmembrane domains of the channel and produced cytoplasmic proteins without channel function. In a reconstituted system, both variants co-precipitated with the full-length channel and induced a robust down-regulation of KV10.1 current when co-expressed with the full-length form, but their effect was mechanistically different. E65 required a tetramerization domain and induced a reduction in the overall expression of full-length KV10.1, whereas E70 mainly affected its glycosylation pattern. E65 triggered the activation of cyclin-dependent kinases in Xenopus laevis oocytes, suggesting a role in cell cycle control. Our observations highlight the relevance of noncanonical functions for the oncogenicity of KV10.1, which need to be considered when ion channels are targeted for cancer therapy.
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Affiliation(s)
| | - Vincenzo Romaniello
- the Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
| | - Araceli Sánchez
- the Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
| | - Claudia Weber
- From the Department of Molecular Biology of Neuronal Signals and
| | | | - Maryna Psol
- From the Department of Molecular Biology of Neuronal Signals and
| | - Luis A Pardo
- the Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
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12
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Babula JJ, Liu JY. Integrate Omics Data and Molecular Dynamics Simulations toward Better Understanding of Human 14-3-3 Interactomes and Better Drugs for Cancer Therapy. J Genet Genomics 2015; 42:531-547. [PMID: 26554908 DOI: 10.1016/j.jgg.2015.09.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 09/03/2015] [Accepted: 09/03/2015] [Indexed: 12/13/2022]
Abstract
The 14-3-3 protein family is among the most extensively studied, yet still largely mysterious protein families in mammals to date. As they are well recognized for their roles in apoptosis, cell cycle regulation, and proliferation in healthy cells, aberrant 14-3-3 expression has unsurprisingly emerged as instrumental in the development of many cancers and in prognosis. Interestingly, while the seven known 14-3-3 isoforms in humans have many similar functions across cell types, evidence of isoform-specific functions and localization has been observed in both healthy and diseased cells. The strikingly high similarity among 14-3-3 isoforms has made it difficult to delineate isoform-specific functions and for isoform-specific targeting. Here, we review our knowledge of 14-3-3 interactome(s) generated by high-throughput techniques, bioinformatics, structural genomics and chemical genomics and point out that integrating the information with molecular dynamics (MD) simulations may bring us new opportunity to the design of isoform-specific inhibitors, which can not only be used as powerful research tools for delineating distinct interactomes of individual 14-3-3 isoforms, but also can serve as potential new anti-cancer drugs that selectively target aberrant 14-3-3 isoform.
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Affiliation(s)
- JoAnne J Babula
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 980 W. Walnut Street, Indianapolis, IN 46202, USA
| | - Jing-Yuan Liu
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 980 W. Walnut Street, Indianapolis, IN 46202, USA; Department of Computer and Information Science, Indiana University Purdue University Indianapolis, 723 W. Michigan St., Indianapolis, IN 46202, USA.
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13
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Slone SR, Lavalley N, McFerrin M, Wang B, Yacoubian TA. Increased 14-3-3 phosphorylation observed in Parkinson's disease reduces neuroprotective potential of 14-3-3 proteins. Neurobiol Dis 2015; 79:1-13. [PMID: 25862939 DOI: 10.1016/j.nbd.2015.02.032] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 12/31/2014] [Accepted: 02/02/2015] [Indexed: 12/21/2022] Open
Abstract
14-3-3 proteins are key regulators of cell survival. We have previously demonstrated that 14-3-3 levels are decreased in an alpha-synuclein (αsyn) mouse model of Parkinson's disease (PD), and that overexpression of certain 14-3-3 isoforms is protective in several PD models. Here we examine whether changes in 14-3-3 phosphorylation may contribute to the neurodegenerative process in PD. We examine three key 14-3-3 phosphorylation sites that normally regulate 14-3-3 function, including serine 58 (S58), serine 184 (S184), and serine/threonine 232 (S/T232), in several models of PD and in human PD brain. We observed that an increase in S232 phosphorylation is observed in rotenone-treated neuroblastoma cells, in cells overexpressing αsyn, and in human PD brains. Alterations in S58 phosphorylation were less consistent in these models, and we did not observe any phosphorylation changes at S184. Phosphorylation at S232 induced by rotenone is reduced by casein kinase inhibitors, and is not dependent on αsyn. Mutation of the S232 site affected 14-3-3θ's neuroprotective effects against rotenone and 1-methyl-4-phenylpyridinium (MPP(+)), with the S232D mutant lacking any protective effect compared to wildtype or S232A 14-3-3θ. The S232D mutant partially reduced the ability of 14-3-3θ to inhibit Bax activation in response to rotenone. Based on these findings, we propose that phosphorylation of 14-3-3s at serine 232 contributes to the neurodegenerative process in PD.
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Affiliation(s)
- Sunny Rae Slone
- Center for Neurodegeneration and Experimental Therapeutics, Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Nicholas Lavalley
- Center for Neurodegeneration and Experimental Therapeutics, Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Michael McFerrin
- Center for Neurodegeneration and Experimental Therapeutics, Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Bing Wang
- Center for Neurodegeneration and Experimental Therapeutics, Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Talene Alene Yacoubian
- Center for Neurodegeneration and Experimental Therapeutics, Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, USA.
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Chuang CC, Jow GM, Lin HM, Weng YH, Hu JH, Peng YJ, Chiu YC, Chiu MM, Jeng CJ. The punctate localization of rat Eag1 K+ channels is conferred by the proximal post-CNBHD region. BMC Neurosci 2014; 15:23. [PMID: 24495567 PMCID: PMC3926332 DOI: 10.1186/1471-2202-15-23] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2013] [Accepted: 01/31/2014] [Indexed: 01/12/2023] Open
Abstract
Background In mammals, Eag K+ channels (KV10) are exclusively expressed in the brain and comprise two isoforms: Eag1 (KV10.1) and Eag2 (KV10.2). Despite their wide presence in various regions of the brain, the functional role of Eag K+ channels remains obscure. Here we address this question by characterizing the subcellular localization of rat Eag1 (rEag1) and rat Eag2 (rEag2) in hippocampal neurons, as well as determining the structural basis underlying their different localization patterns. Results Immunofluorescence analysis of young and mature hippocampal neurons in culture revealed that endogenous rEag1 and rEag2 K+ channels were present in both the dendrosomatic and the axonal compartments. Only rEag1 channels displayed a punctate immunostaining pattern and showed significant co-localization with PSD-95. Subcellular fractionation analysis further demonstrated a distinct enrichment of rEag1 in the synaptosomal fraction. Over-expression of recombinant GFP-tagged Eag constructs in hippocampal neurons also showed a significant punctate localization of rEag1 channels. To identify the protein region dictating the Eag channel subcellular localization pattern, we generated a variety of different chimeric constructs between rEag1 and rEag2. Quantitative studies of neurons over-expressing these GFP-tagged chimeras indicated that punctate localization was conferred by a segment (A723-R807) within the proximal post-cyclic nucleotide-binding homology domain (post-CNBHD) region in the rEag1 carboxyl terminus. Conclusions Our findings suggest that Eag1 and Eag2 K+ channels may modulate membrane excitability in both the dendrosomatic and the axonal compartments and that Eag1 may additionally regulate neurotransmitter release and postsynaptic signaling. Furthermore, we present the first evidence showing that the proximal post-CNBHD region seems to govern the Eag K+ channel subcellular localization pattern.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Chung-Jiuan Jeng
- Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, No, 155, Section 2, Li-Non Street, Taipei 12212, Taiwan.
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