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Mott TM, Wulffraat GC, Eddins AJ, Mehl RA, Senning EN. Fluorescence labeling strategies for the study of ion channel and receptor cell surface expression: A comprehensive toolkit for extracellular labeling of TRPV1. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.09.593209. [PMID: 39005265 PMCID: PMC11244879 DOI: 10.1101/2024.05.09.593209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Regulation of ion channel expression on the plasma membrane is a major determinant of neuronal excitability, and identifying the underlying mechanisms of this expression is critical to our understanding of neurons. A critical aspect of measuring changes in ion channel expression is uniquely identifying ion channels located on the cell surface. To accomplish this goal we demonstrate two orthogonal strategies to label extracellular sites of the ion channel TRPV1 that minimally perturb the function of the channel: 1) We use the amber codon suppression technique to introduce a non-canonical amino acid (ncAA) with tetrazine click chemistry compatible with a trans-cyclooctene coupled fluorescent dye. 2) By inserting the circularly permutated HaloTag (cpHaloTag) in an extracellular loop of TRPV1, we incorporate a click-chemistry site for a chloroalkane-linked fluorescent dye of our choosing. Optimization of ncAA insertion sites was accomplished by screening residue positions between the S1 and S2 transmembrane domains with elevated missense variants in the human population, and we identified T468 as a rapid labeling site (~5 minutes) based on functional as well as biochemical assays in HEK293T/17 cells. After several rounds of adapting the linker lengths and backbone placement of cpHaloTag on the extracellular side of TRPV1, our efforts led to a channel construct that robustly expressed as a fully functional TRPV1exCellHalo fusion with intact wild-type gating properties. The TRPV1exCellHalo construct was used in a single molecule experiment to track TRPV1 on the cell surface and validate studies that show decreased mobility of the channel upon activation. The success of these extracellular label TRPV1 (exCellTRPV1) constructs as tools to track surface expression of the channel will shed significant light on the mechanisms regulating expression and provide a general scheme to introduce similar modifications to other cell surface receptors.
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Tsui JC, Aleman TS, Tapino PJ, Kim BJ. Detailed Phenotype Supports Pathogenicity of Hypomorphic Variant in ABCC6-Associated Pattern Dystrophy. Case Rep Ophthalmol 2024; 15:497-506. [PMID: 39015234 PMCID: PMC11250126 DOI: 10.1159/000538045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 02/25/2024] [Indexed: 07/18/2024] Open
Abstract
Introduction We report a case of pseudoxanthoma elasticum (PXE) with an atypical phenotype likely related to a hypomorphic variant in ABCC6. Case Presentation A 66-year-old Caucasian female with a history of a maculopathy interpreted as either age-related macular degeneration or a pattern dystrophy underwent a detailed ophthalmic evaluation. Visual acuities were 20/25, OD, and 20/20, OS. Spectral domain optical coherence and fluorescein angiography demonstrated outer retinal disruptions and breaks in retinal pigment epithelium (RPE)/Bruch's membrane bilaterally, consistent with angioid streaks. A large area of hypo- and hyperautofluorescence extending from the central retina into the peripapillary retina was documented with short-wavelength excitation autofluorescence. The area of hypoautofluorescence, which was much larger on near-infrared excitation, spared the temporal retina. Two-color dark-adapted perimetries documented severe rod sensitivity losses and less severe cone sensitivity abnormalities co-localizing with the RPE abnormalities. No obvious skin findings were observed, and initial dermatologic biopsy was negative. Gene screening identified a pathogenic ABCC6 gene variant c.1552C>T and a previously reported variant of uncertain significance c.1171A>G. A second dermatologic biopsy demonstrated positive findings consistent with PXE. Conclusion Although this patient had minimal skin findings, this patient had characteristic structural and functional abnormalities of a pattern dystrophy with angioid streaks and histologic evidence of PXE, suggesting compound heterozygous variants involving the hypomorphic ABCC6 c.1171A>G variant. These findings support the pathogenic role of both variants.
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Affiliation(s)
- Jonathan C. Tsui
- Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Ophthalmology, Veterans Affairs New Jersey Healthcare System, East Orange, NJ, USA
| | - Tomas S. Aleman
- Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Center for Advanced Retinal and Ocular Therapeutics (CAROT), University of Pennsylvania, Philadelphia, PA, USA
- Division of Ophthalmology, Children’s Hospital of Philadelphia (CHOP), Philadelphia, PA, USA
| | - Paul J. Tapino
- Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Benjamin J. Kim
- Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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Liu Y, Huang Y, Zhang X, Ma X, He X, Gan C, Zou X, Wang S, Shu K, Lei T, Zhang H. CircZXDC Promotes Vascular Smooth Muscle Cell Transdifferentiation via Regulating miRNA-125a-3p/ABCC6 in Moyamoya Disease. Cells 2022; 11:cells11233792. [PMID: 36497052 PMCID: PMC9741004 DOI: 10.3390/cells11233792] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/23/2022] [Accepted: 11/24/2022] [Indexed: 11/29/2022] Open
Abstract
Moyamoya disease (MMD) is an occlusive, chronic cerebrovascular disease affected by genetic mutation and the immune response. Furthermore, vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) participate in the neointima of MMD, but the etiology and pathophysiological changes in MMD vessels remain largely unknown. Therefore, we established the circZXDC (ZXD family zinc finger C)-miR-125a-3p-ABCC6 (ATP-binding cassette subfamily C member 6) axis from public datasets and online tools based on "sponge-like" interaction mechanisms to investigate its possible role in VSMCs. The results from a series of in vitro experiments, such as dual luciferase reporter assays, cell transfection, CCK-8 assays, Transwell assays, and Western blotting, indicate a higher level of circZXDC in the MMD plasma, especially in those MMD patients with the RNF213 mutation. Moreover, circZXDC overexpression results in a VSMC phenotype switching toward a synthetic status, with increased proliferation and migration activity. CircZXDC sponges miR-125a-3p to increase ABCC6 expression, which induces ERS (endoplasmic reticulum stress), and subsequently regulates VSMC transdifferentiation from the contractive phenotype to the synthetic phenotype, contributing to the intima thickness of MMD vessels. Our findings provide insight into the pathophysiological mechanisms of MMD and indicate that the circZXDC-miR-125a-3p-ABCC6 axis plays a pivotal role in the progression of MMD. Furthermore, circZXDC might be a diagnostic biomarker and an ABCC6-specific inhibitor and has the potential to become a promising therapeutic option for MMD.
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Affiliation(s)
- Yuan Liu
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Yimin Huang
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Xincheng Zhang
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Xiaopeng Ma
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Xuejun He
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Chao Gan
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Xin Zou
- Institute of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Sheng Wang
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Kai Shu
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Ting Lei
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Huaqiu Zhang
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
- Correspondence:
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Szeri F, Niaziorimi F, Donnelly S, Fariha N, Tertyshnaia M, Patel D, Lundkvist S, van de Wetering K. The Mineralization Regulator ANKH Mediates Cellular Efflux of ATP, Not Pyrophosphate. J Bone Miner Res 2022; 37:1024-1031. [PMID: 35147247 PMCID: PMC9098669 DOI: 10.1002/jbmr.4528] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 01/28/2022] [Accepted: 02/08/2022] [Indexed: 11/05/2022]
Abstract
The plasma membrane protein ankylosis homologue (ANKH, mouse ortholog: Ank) prevents pathological mineralization of joints by controlling extracellular levels of the mineralization inhibitor pyrophosphate (PPi). It was long thought that ANKH acts by transporting PPi into the joints. We recently showed that when overproduced in HEK293 cells, ANKH mediates release of large amounts of nucleoside triphosphates (NTPs), predominantly ATP, into the culture medium. ATP is converted extracellularly into PPi and AMP by the ectoenzyme ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1). We could not rule out, however, that cells also release PPi directly via ANKH. We now addressed the question of whether PPi leaves cells via ANKH using HEK293 cells that completely lack ENPP1. Introduction of ANKH in these ENPP1-deficient HEK293 cells resulted in robust cellular ATP release without the concomitant increase in extracellular PPi found in ENPP1-proficient cells. Ank activity was previously shown to be responsible for about 75% of the PPi found in mouse bones. However, bones of Enpp1-/- mice contained <2.5% of the PPi found in bones of wild-type mice, showing that Enpp1 activity is also a prerequisite for Ank-dependent PPi incorporation into the mineralized bone matrix in vivo. Hence, ATP release precedes ENPP1-mediated PPi formation. We find that ANKH also provides about 25% of plasma PPi, whereas we have previously shown that 60% to 70% of plasma PPi is derived from the NTPs extruded by the ABC transporter, ABCC6. Both transporters that keep plasma PPi at sufficient levels to prevent pathological calcification therefore do so by extruding NTPs rather than PPi itself. © 2022 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Flora Szeri
- Department of Dermatology and Cutaneous Biology, Jefferson Institute of Molecular Medicine and PXE International Center of Excellence in Research and Clinical Care, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA.,Research Centre for Natural Sciences, Institute of Enzymology, Budapest, Hungary.,Department of Biochemistry, Semmelweis University, Budapest, Hungary
| | - Fatemeh Niaziorimi
- Department of Dermatology and Cutaneous Biology, Jefferson Institute of Molecular Medicine and PXE International Center of Excellence in Research and Clinical Care, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Sylvia Donnelly
- Department of Dermatology and Cutaneous Biology, Jefferson Institute of Molecular Medicine and PXE International Center of Excellence in Research and Clinical Care, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Nishat Fariha
- Department of Dermatology and Cutaneous Biology, Jefferson Institute of Molecular Medicine and PXE International Center of Excellence in Research and Clinical Care, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Mariia Tertyshnaia
- Department of Dermatology and Cutaneous Biology, Jefferson Institute of Molecular Medicine and PXE International Center of Excellence in Research and Clinical Care, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Drithi Patel
- Department of Dermatology and Cutaneous Biology, Jefferson Institute of Molecular Medicine and PXE International Center of Excellence in Research and Clinical Care, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Stefan Lundkvist
- Department of Dermatology and Cutaneous Biology, Jefferson Institute of Molecular Medicine and PXE International Center of Excellence in Research and Clinical Care, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Koen van de Wetering
- Department of Dermatology and Cutaneous Biology, Jefferson Institute of Molecular Medicine and PXE International Center of Excellence in Research and Clinical Care, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
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Hamdoun A, Hellmich UA, Szakacs G, Kuchler K. The incredible diversity of structures and functions of ABC transporters. FEBS Lett 2021; 595:671-674. [PMID: 33754351 DOI: 10.1002/1873-3468.14061] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Amro Hamdoun
- Scripps Institution of Oceanography, UC San Diego, CA, USA
| | - Ute A Hellmich
- Institute of Organic Chemistry and Macromolecular Chemistry, Cluster of Excellence 'Balance of the Microverse', Friedrich-Schiller-University Jena, Germany
| | - Gergely Szakacs
- Institute of Enzymology, Research Centre of Natural Sciences, Eötvös Loránd Research Network, Budapest, Hungary.,Institute of Cancer Research, Medical University of Vienna, Austria
| | - Karl Kuchler
- Max F. Perutz Laboratories, Department of Medical Biochemistry, Medical University Vienna, Austria
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RAB10 Interacts with ABCB4 and Regulates Its Intracellular Traffic. Int J Mol Sci 2021; 22:ijms22137087. [PMID: 34209301 PMCID: PMC8268348 DOI: 10.3390/ijms22137087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 06/28/2021] [Accepted: 06/29/2021] [Indexed: 12/11/2022] Open
Abstract
ABCB4 (ATP-binding cassette subfamily B member 4) is an ABC transporter expressed at the canalicular membrane of hepatocytes where it ensures phosphatidylcholine secretion into bile. Genetic variations of ABCB4 are associated with several rare cholestatic diseases. The available treatments are not efficient for a significant proportion of patients with ABCB4-related diseases and liver transplantation is often required. The development of novel therapies requires a deep understanding of the molecular mechanisms regulating ABCB4 expression, intracellular traffic, and function. Using an immunoprecipitation approach combined with mass spectrometry analyses, we have identified the small GTPase RAB10 as a novel molecular partner of ABCB4. Our results indicate that the overexpression of wild type RAB10 or its dominant-active mutant significantly increases the amount of ABCB4 at the plasma membrane expression and its phosphatidylcholine floppase function. Contrariwise, RAB10 silencing induces the intracellular retention of ABCB4 and then indirectly diminishes its secretory function. Taken together, our findings suggest that RAB10 regulates the plasma membrane targeting of ABCB4 and consequently its capacity to mediate phosphatidylcholine secretion.
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Szeri F, Corradi V, Niaziorimi F, Donnelly S, Conseil G, Cole SPC, Tieleman DP, van de Wetering K. Mutagenic Analysis of the Putative ABCC6 Substrate-Binding Cavity Using a New Homology Model. Int J Mol Sci 2021; 22:ijms22136910. [PMID: 34199119 PMCID: PMC8267652 DOI: 10.3390/ijms22136910] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Revised: 06/19/2021] [Accepted: 06/23/2021] [Indexed: 12/16/2022] Open
Abstract
Inactivating mutations in ABCC6 underlie the rare hereditary mineralization disorder pseudoxanthoma elasticum. ABCC6 is an ATP-binding cassette (ABC) integral membrane protein that mediates the release of ATP from hepatocytes into the bloodstream. The released ATP is extracellularly converted into pyrophosphate, a key mineralization inhibitor. Although ABCC6 is firmly linked to cellular ATP release, the molecular details of ABCC6-mediated ATP release remain elusive. Most of the currently available data support the hypothesis that ABCC6 is an ATP-dependent ATP efflux pump, an un-precedented function for an ABC transporter. This hypothesis implies the presence of an ATP-binding site in the substrate-binding cavity of ABCC6. We performed an extensive mutagenesis study using a new homology model based on recently published structures of its close homolog, bovine Abcc1, to characterize the substrate-binding cavity of ABCC6. Leukotriene C4 (LTC4), is a high-affinity substrate of ABCC1. We mutagenized fourteen amino acid residues in the rat ortholog of ABCC6, rAbcc6, that corresponded to the residues in ABCC1 found in the LTC4 binding cavity. Our functional characterization revealed that most of the amino acids in rAbcc6 corresponding to those found in the LTC4 binding pocket in bovine Abcc1 are not critical for ATP efflux. We conclude that the putative ATP binding site in the substrate-binding cavity of ABCC6/rAbcc6 is distinct from the bovine Abcc1 LTC4-binding site.
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Affiliation(s)
- Flora Szeri
- Department of Dermatology and Cutaneous Biology and PXE Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA 19107, USA; (F.S.); (F.N.); (S.D.)
- Research Centre for Natural Sciences, Institute of Enzymology, 1117 Budapest, Hungary
| | - Valentina Corradi
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, Calgary, AB T2N 1N4, Canada; (V.C.); (D.P.T.)
| | - Fatemeh Niaziorimi
- Department of Dermatology and Cutaneous Biology and PXE Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA 19107, USA; (F.S.); (F.N.); (S.D.)
| | - Sylvia Donnelly
- Department of Dermatology and Cutaneous Biology and PXE Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA 19107, USA; (F.S.); (F.N.); (S.D.)
| | - Gwenaëlle Conseil
- Department of Pathology and Molecular Medicine, Queen’s University, Kingston, ON K7L 3N6, Canada; (G.C.); (S.P.C.C.)
| | - Susan P. C. Cole
- Department of Pathology and Molecular Medicine, Queen’s University, Kingston, ON K7L 3N6, Canada; (G.C.); (S.P.C.C.)
| | - D. Peter Tieleman
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, Calgary, AB T2N 1N4, Canada; (V.C.); (D.P.T.)
| | - Koen van de Wetering
- Department of Dermatology and Cutaneous Biology and PXE Center of Excellence in Research and Clinical Care, Thomas Jefferson University, Philadelphia, PA 19107, USA; (F.S.); (F.N.); (S.D.)
- Correspondence: ; Tel.: +1-(215)-503-5701
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