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Chang G, Aroge FA, Venkateshappa R, Claydon TW, Sun B. Development of an Absolute Quantification Method for hERG Using PRM with Single Isotopologue in-Sample Calibration. ACS OMEGA 2024; 9:33972-33982. [PMID: 39130540 PMCID: PMC11308013 DOI: 10.1021/acsomega.4c04541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2024] [Revised: 06/20/2024] [Accepted: 06/21/2024] [Indexed: 08/13/2024]
Abstract
The human ether-à-go-go-related gene (KCNH2)-encoded protein hERG constitutes the α subunit of the Kv11.1 channel and contributes to the I kr current, which plays an important role in the cardiac action potential. Genetically and xenobiotically triggered malfunctions of hERG can cause arrhythmia. The expression of hERG in various study systems was assessed mainly as the fold change relative to the corresponding control. Here, we developed a simple and sensitive quantitation method using targeted mass spectrometry, i.e., the parallel reaction monitoring approach, to measure the absolute quantity of hERG in copy number. Such measurements do not require controls, and the obtained values can be compared with similar results for any other protein. To effectively avoid matrix effects, we used the heavy-match-light (HML) in-sample calibration approach that requires only a single isotopologue to achieve copy-number quantitation. No significant difference was observed in the results obtained by HML and by the classic standard addition in-sample calibration approach. Using four proteotypic peptides, we quantified the average number of copies of hERG in the HEK293T heterologous expression system as 3.6 ± 0.5 × 106 copies/cell, i.e., 1 million copies/cell for the fully assembled Kv11.1 channel.
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Affiliation(s)
- Ge Chang
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A1S6, Canada
| | - Fabusuyi A. Aroge
- School
of Mechatronic Systems Engineering, Simon
Fraser University, Surrey, British Columbia V3T0A3, Canada
| | - Ravichandra Venkateshappa
- Department
of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A1S6, Canada
| | - Tom W. Claydon
- Department
of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A1S6, Canada
| | - Bingyun Sun
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A1S6, Canada
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2
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Francis CR, Bell ML, Skripnichuk MM, Kushner EJ. Arf6 is required for endocytosis and filamentous actin assembly during angiogenesis in vitro. Microcirculation 2023; 30:e12831. [PMID: 37750425 PMCID: PMC10688150 DOI: 10.1111/micc.12831] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 08/24/2023] [Accepted: 09/13/2023] [Indexed: 09/27/2023]
Abstract
OBJECTIVE Endocytosis is a process vital to angiogenesis and vascular homeostasis. In pathologies where supraphysiological growth factor signaling underlies disease etiology, such as in diabetic retinopathy and solid tumors, strategies to limit chronic growth factor signaling by way of blunting endocytic processes have been shown to have tremendous clinical value. ADP ribosylation factor 6 (Arf6) is a small GTPase that promotes the assembly of actin necessary for clathrin-mediated and clathrin-independent endocytosis. In its absence, growth factor signaling is greatly diminished, which has been shown to ameliorate pathological signaling input in diseased vasculature. However, it is less clear if there are bystander effects related to loss of Arf6 on angiogenic behaviors. Our goal was to provide an analysis of Arf6's function in angiogenic endothelium, focusing on its role in actin and endocytosis as well as sprouting morphogenesis. METHODS Primary endothelial cells were cultured in both 2D and 3D environments. Here, endothelial cells were fixed and stained for various proteins or transfected with fluorescently-tagged constructs for live-cell imaging. RESULTS We found that Arf6 localized to both filamentous actin and sites of endocytosis in two-dimensional culture. Loss of Arf6 distorted both apicobasal polarity and reduced the total cellular filamentous actin content, which may be the primary driver underlying gross sprouting dysmorphogenesis in its absence. CONCLUSIONS Our findings highlight that endothelial Arf6 is a potent mediator of both actin regulation and endocytosis and is required for proper sprout formation.
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Affiliation(s)
| | - Makenzie L. Bell
- Department of Biological Sciences, University of Denver, Denver, CO
| | | | - Erich J. Kushner
- Department of Biological Sciences, University of Denver, Denver, CO
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3
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Nguyen NH, Brodsky JL. The cellular pathways that maintain the quality control and transport of diverse potassium channels. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2023; 1866:194908. [PMID: 36638864 PMCID: PMC9908860 DOI: 10.1016/j.bbagrm.2023.194908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/20/2022] [Accepted: 01/03/2023] [Indexed: 01/12/2023]
Abstract
Potassium channels are multi-subunit transmembrane proteins that permit the selective passage of potassium and play fundamental roles in physiological processes, such as action potentials in the nervous system and organismal salt and water homeostasis, which is mediated by the kidney. Like all ion channels, newly translated potassium channels enter the endoplasmic reticulum (ER) and undergo the error-prone process of acquiring post-translational modifications, folding into their native conformations, assembling with other subunits, and trafficking through the secretory pathway to reach their final destinations, most commonly the plasma membrane. Disruptions in these processes can result in detrimental consequences, including various human diseases. Thus, multiple quality control checkpoints evolved to guide potassium channels through the secretory pathway and clear potentially toxic, aggregation-prone misfolded species. We will summarize current knowledge on the mechanisms underlying potassium channel quality control in the secretory pathway, highlight diseases associated with channel misfolding, and suggest potential therapeutic routes.
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Affiliation(s)
- Nga H Nguyen
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA.
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4
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Shroka TM, Kufareva I, Salanga CL, Handel TM. The dual-function chemokine receptor CCR2 drives migration and chemokine scavenging through distinct mechanisms. Sci Signal 2023; 16:eabo4314. [PMID: 36719944 PMCID: PMC10091583 DOI: 10.1126/scisignal.abo4314] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
C-C chemokine receptor 2 (CCR2) is a dual-function receptor. Similar to other G protein-coupled chemokine receptors, it promotes monocyte infiltration into tissues in response to the chemokine CCL2, and, like atypical chemokine receptors (ACKRs), it scavenges chemokine from the extracellular environment. CCR2 therefore mediates CCL2-dependent signaling as a G protein-coupled receptor (GPCR) and also limits CCL2 signaling as a scavenger receptor. We investigated the mechanisms underlying CCR2 scavenging, including the involvement of intracellular proteins typically associated with GPCR signaling and internalization. Using CRISPR knockout cell lines, we showed that CCR2 scavenged by constitutively internalizing to remove CCL2 from the extracellular space and recycling back to the cell surface for further rounds of ligand sequestration. This process occurred independently of G proteins, GPCR kinases (GRKs), β-arrestins, and clathrin, which is distinct from other "professional" chemokine scavenger receptors that couple to GRKs, β-arrestins, or both. These findings set the stage for understanding the molecular regulators that determine CCR2 scavenging and may have implications for drug development targeting this therapeutically important receptor.
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Affiliation(s)
- Thomas M Shroka
- Biomedical Sciences Program, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Irina Kufareva
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Catherina L Salanga
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Tracy M Handel
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA
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Chidipi B, Chang M, Abou-Assali O, Reiser M, Tian Z, Allen-Gipson D, Noujaim SF. The Arf6/PIP5K pathway activates IKACh in cigarette smoke mediated atrial fibrillation. Cell Signal 2022; 100:110475. [PMID: 36150420 DOI: 10.1016/j.cellsig.2022.110475] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 08/29/2022] [Accepted: 09/16/2022] [Indexed: 11/29/2022]
Abstract
Cigarette smoking (CS) is a major cause of cardiovascular diseases. Smokers are at a significantly higher risk for developing atrial fibrillation (AF), a dangerous and abnormal heart rhythm. In the US, 15.5% of adults are current smokers, and it is becoming clear that CS is an independent risk factor for AF, but a detailed mechanistic understanding of how CS contributes to the molecular patho-electrophysiology of AF remains elusive. We investigated if CS related AF is in part mediated through a mechanism that depends on the cardiac acetylcholine activated inward rectifier potassium current (IKACh). We tested the hypothesis that CS increases IKACh via phosphatidylinositol 4-phosphate 5-kinase alpha (PIP5K) and ADP ribosylation factor 6 (Arf6) signaling, leading to AF perpetuation. In vivo inducibility of AF was assessed in mice exposed to CS for 8 weeks. AF duration was increased in CS exposed mice, and TertiapinQ, an IKACh blocker prevented AF development in CS exposed mice. In HEK293 cells stably transfected with Kir3.1 and Kir3.4, the molecular correlates of IKACh, CS exposure increased the expression of the Kir3.1 and Kir3.4 proteins at the cell surface, activated Arf6 and increased the IKACh current. Inhibition of PIP5K, or of Kir3.1/Kir3.4 trafficking via Arf6 abrogated the CS effects on IKACh. Cigarette smoke modifies the atrial electrophysiological substrate, leading to arrhythmogenesis, in part, through IKACh activation via an Arf6/PIP5K dependent pathway.
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Affiliation(s)
- Bojjibabu Chidipi
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL, United States of America..
| | - Mengmeng Chang
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL, United States of America
| | - Obada Abou-Assali
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL, United States of America
| | - Michelle Reiser
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL, United States of America
| | - Zhi Tian
- Department of Pharmaceutical Science, USF Health Taneja College of Pharmacy, University of South Florida, Tampa, FL, United States of America
| | - Diane Allen-Gipson
- Department of Pharmaceutical Science, USF Health Taneja College of Pharmacy, University of South Florida, Tampa, FL, United States of America
| | - Sami F Noujaim
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL, United States of America
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Internalization of Polymeric Bacterial Peptidoglycan Occurs through Either Actin or Dynamin Dependent Pathways. Microorganisms 2022; 10:microorganisms10030552. [PMID: 35336127 PMCID: PMC8951193 DOI: 10.3390/microorganisms10030552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 02/28/2022] [Accepted: 02/28/2022] [Indexed: 01/27/2023] Open
Abstract
Peptidoglycan (PGN), a polymeric glycan macromolecule, is a major constituent of the bacterial cell wall and a conserved pathogen-associated molecular pattern (PAMP) that triggers immune responses through cytosolic sensors. Immune cells encounter both PGN polymers and hydrolyzed muropeptides during infections, and primary human innate immune cells respond better to polymeric PGN than the minimal bioactive subunit muramyl dipeptide (MDP). While MDP is internalized through macropinocytosis and/or clathrin-mediated endocytosis, the internalization of particulate polymeric PGN is unresolved. We show here that PGN macromolecules isolated from Bacillus anthracis display a broad range of sizes, making them amenable for multiple internalization pathways. Pharmacologic inhibition indicates that PGN primarily, but not exclusively, is internalized by actin-dependent endocytosis. An alternate clathrin-independent but dynamin dependent pathway supports 20–30% of PGN uptake. In primary monocytes, this alternate pathway does not require activities of RhoA, Cdc42 or Arf6 small GTPases. Selective inhibition of PGN uptake shows that phagolysosomal trafficking, processing and downstream immune responses are drastically affected by actin depolymerization, while dynamin inhibition has a smaller effect. Overall, we show that polymeric PGN internalization occurs through two endocytic pathways with distinct potentials to trigger immune responses.
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Gao J, Qiu Y, Hou Y, Zhang L, Wang K, Chen Z, Liu Q, Lin J. Influencing factors for the decline of limb muscle strength and the association with all-cause mortality: evidence from a nationwide population-based cohort study. Aging Clin Exp Res 2022; 34:399-407. [PMID: 34313962 DOI: 10.1007/s40520-021-01940-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 07/13/2021] [Indexed: 10/20/2022]
Abstract
BACKGROUND The decline of muscle strength, a typical characteristic of sarcopenia, greatly affects aging-related health outcomes; however, prospective data on influencing factors and mortality in the Chinese population are relatively sparse. AIMS We investigated the influencing factors for the declined limb muscle strength and the association with all-cause mortality among the elderly Chinese individuals aged ≥ 65 years in a large long-term prospective cohort study. METHODS We used data from the China Health and Retirement Longitudinal Study (CHARLS). Logistic regression analyses were performed to investigate the influencing factors of declined limb muscle strength. Cox proportional hazard models were used to analyze the impact on all-cause mortality, whose performance was evaluated by train-test cross-validation. RESULTS The prevalences of declined upper and lower limb strength, which were defined by low hand grip strength (HS) and gait speed (GS), respectively, were 34.4% and 59.7%. The declined HS was significantly associated with older age (p < 0.001), female (p < 0.001), lower educational level (p < 0.001), lower BMI (p < 0.001), and combined with chronic diseases (p = 0.001). Moreover, the declined limb muscle strength was correlated with all-cause mortality (HR: 1.13, 95% CI 1.03-1.21 for HS; HR: 1.09, 95% CI 1.04-1.15 for GS), according to a multi-adjusted model with moderate predictive ability (C-index: 0.714, AUC of 7 year follow-up: 0.716). CONCLUSIONS The decline of limb muscle strength was prevalent among elderly Chinese individuals and had a strong impact on all-cause mortality. Identification of key populations and tailored interventions on their influencing factors should be implemented in further research.
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Zheng W, Li T, Wei J, Zhang Y, Zuo Q, Lin Y. Identification of miR-145 as a regulator of the cardiomyocyte inflammatory response and oxidative stress under hyperglycemia. Exp Ther Med 2021; 21:467. [PMID: 33763154 PMCID: PMC7983182 DOI: 10.3892/etm.2021.9898] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 10/23/2020] [Indexed: 12/14/2022] Open
Abstract
The current study aimed to explore the effects of microRNA (miR)-145 on the inflammatory response and oxidative stress (OS) in high glucose (HG)-induced cardiomyocytes, as well as the specific mechanism underlying this action. H9c2 cells were treated with 33 mmol/l glucose (HG group) or cotreated with 24.5 mmol/l mannitol and 5.5 mmol/l glucose (hypertonic group), and the expression levels of miR-145 and ADP ribosylation factor 6 (ARF6) were detected. The cells were transfected with pcDNA3.1-ARF6, miR-145 mimics or corresponding negative controls prior to the assessment of cell survival rate. Levels of lactate dehydrogenase (LDH), reactive oxygen species (ROS) and malondialdehyde (MDA), as well as the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), and the levels of IL-6, TNF-α and monocyte chemoattractant protein-1 (MCP-1) were subsequently determined. The apoptotic rate of H9c2 cells was examined by flow cytometry. The interaction between miR-145-ARF6 was predicted and confirmed by luciferase reporter assays. In the HG group, miR-145 expression was significantly decreased and ARF6 expression significantly increased compared with controls. Furthermore, the levels of inflammatory factors (IL-6, TNF-α and MCP-1), LDH, ROS and MDA were significantly elevated in the HG group compared with controls. Significantly decreased SOD, CAT and GPx activities and significantly increased numbers of apoptotic cells were observed in the HG group compared with controls. The cells transfected with miR-145 mimics exhibited significantly decreased LDH, ROS and MDA levels, significantly increased antioxidant enzyme activities and significantly decreased apoptotic rates compared with controls, while the opposite results were observed in cells transfected with pcDNA3.1-ARF6. Moreover, co-transfection with miR-145 mimics and pcDNA3.1-ARF6 exacerbated the inflammatory response and OS injury in HG-induced cardiomyocytes compared with cells transfected with miR-145 mimics alone. Furthermore, miR-145 negatively targeted ARF6. miR-145 attenuated the HG-induced inflammatory response and OS injury in cardiomyocytes by negatively regulating ARF6, which may contribute to providing a theoretical basis for the treatment of diabetic cardiomyopathy.
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Affiliation(s)
- Wan Zheng
- Department of Cardiovascular Internal Medicine, The First Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570102, P.R. China
| | - Tianfa Li
- Department of Cardiovascular Internal Medicine, The First Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570102, P.R. China
| | - Junping Wei
- Department of Cardiovascular Internal Medicine, The First Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570102, P.R. China
| | - Yuanyuan Zhang
- Department of Cardiovascular Internal Medicine, The First Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570102, P.R. China
| | - Qi Zuo
- Department of Cardiovascular Internal Medicine, The First Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570102, P.R. China
| | - Yun Lin
- Department of Cardiovascular Internal Medicine, The First Affiliated Hospital of Hainan Medical University, Haikou, Hainan 570102, P.R. China
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Estadella I, Pedrós-Gámez O, Colomer-Molera M, Bosch M, Sorkin A, Felipe A. Endocytosis: A Turnover Mechanism Controlling Ion Channel Function. Cells 2020; 9:E1833. [PMID: 32759790 PMCID: PMC7463639 DOI: 10.3390/cells9081833] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/30/2020] [Accepted: 08/02/2020] [Indexed: 01/08/2023] Open
Abstract
Ion channels (IChs) are transmembrane proteins that selectively drive ions across membranes. The function of IChs partially relies on their abundance and proper location in the cell, fine-tuned by the delicate balance between secretory, endocytic, and degradative pathways. The disruption of this balance is associated with several diseases, such as Liddle's and long QT syndromes. Because of the vital role of these proteins in human health and disease, knowledge of ICh turnover is essential. Clathrin-dependent and -independent mechanisms have been the primary mechanisms identified with ICh endocytosis and degradation. Several molecular determinants recognized by the cellular internalization machinery have been discovered. Moreover, specific conditions can trigger the endocytosis of many IChs, such as the activation of certain receptors, hypokalemia, and some drugs. Ligand-dependent receptor activation primarily results in the posttranslational modification of IChs and the recruitment of important mediators, such as β-arrestins and ubiquitin ligases. However, endocytosis is not a final fate. Once internalized into endosomes, IChs are either sorted to lysosomes for degradation or recycled back to the plasma membrane. Rab proteins are crucial participants during these turnover steps. In this review, we describe the major ICh endocytic pathways, the signaling inputs triggering ICh internalization, and the key mediators of this essential cellular process.
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Affiliation(s)
- Irene Estadella
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
| | - Oriol Pedrós-Gámez
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
| | - Magalí Colomer-Molera
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
| | - Manel Bosch
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
- Centres Científics i Tecnològics de la Universitat de Barcelona (CCiTUB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Alexander Sorkin
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA;
| | - Antonio Felipe
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
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Parks XX, Ronzier E, O-Uchi J, Lopes CM. Fluvastatin inhibits Rab5-mediated IKs internalization caused by chronic Ca 2+-dependent PKC activation. J Mol Cell Cardiol 2019; 129:314-325. [PMID: 30898664 DOI: 10.1016/j.yjmcc.2019.03.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 02/26/2019] [Accepted: 03/16/2019] [Indexed: 10/27/2022]
Abstract
Statins, in addition to their cholesterol lowering effects, can prevent isoprenylation of Rab GTPase proteins, a key protein family for the regulation of protein trafficking. Rab-GTPases have been shown to be involved in the control of membrane expression level of ion channels, including one of the major cardiac repolarizing channels, IKs. Decreased IKs function has been observed in a number of disease states and associated with increased propensity for arrhythmias, but the mechanism underlying IKs decrease remains elusive. Ca2+-dependent PKC isoforms (cPKC) are chronically activated in variety of human diseases and have been suggested to acutely regulate IKs function. We hypothesize that chronic cPKC stimulation leads to Rab-mediated decrease in IKs membrane expression, and that can be prevented by statins. In this study we show that chronic cPKC stimulation caused a dramatic Rab5 GTPase-dependent decrease in plasma membrane localization of the IKs pore forming subunit KCNQ1, reducing IKs function. Our data indicates fluvastatin inhibition of Rab5 restores channel localization and function after cPKC-mediated channel internalization. Our results indicate a novel statin anti-arrhythmic effect that would be expected to inhibit pathological electrical remodeling in a number of disease states associated with high cPKC activation. Because Rab-GTPases are important regulators of membrane trafficking they may underlie other statin pleiotropic effects.
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Affiliation(s)
- Xiaorong Xu Parks
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, United States of America
| | - Elsa Ronzier
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, United States of America
| | - Jin O-Uchi
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, United States of America; Lillehei Heart Institute, University of Minnesota, 2231 6th Street SE, Minneapolis, MN 55455, United States of America
| | - Coeli M Lopes
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, United States of America.
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11
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Kanner SA, Jain A, Colecraft HM. Development of a High-Throughput Flow Cytometry Assay to Monitor Defective Trafficking and Rescue of Long QT2 Mutant hERG Channels. Front Physiol 2018; 9:397. [PMID: 29725305 PMCID: PMC5917007 DOI: 10.3389/fphys.2018.00397] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 04/04/2018] [Indexed: 11/24/2022] Open
Abstract
Long QT Syndrome (LQTS) is an acquired or inherited disorder characterized by prolonged QT interval, exertion-triggered arrhythmias, and sudden cardiac death. One of the most prevalent hereditary LQTS subtypes, LQT2, results from loss-of-function mutations in the hERG channel, which conducts IKr, the rapid component of the delayed rectifier K+ current, critical for cardiac repolarization. The majority of LQT2 mutations result in Class 2 deficits characterized by impaired maturation and trafficking of hERG channels. Here, we have developed a high-throughput flow cytometric assay to analyze the surface and total expression of wild-type (WT) and mutant hERG channels with single-cell resolution. To test our method, we focused on 16 LQT2 mutations in the hERG Per-Arnt-Sim (PAS) domain that were previously studied via a widely used biochemical approach that compares levels of 135-kDa immature and 155-kDa fully glycosylated hERG protein to infer surface expression. We confirmed that LQT2 mutants expressed in HEK293 cells displayed a decreased surface density compared to WT hERG, and were differentially rescued by low temperature. However, we also uncovered some notable differences from the findings obtained via the biochemical approach. In particular, three mutations (N33T, R56Q, and A57P) with apparent WT-like hERG glycosylation patterns displayed up to 50% decreased surface expression. Furthermore, despite WT-like levels of complex glycosylation, these mutants have impaired forward trafficking, and exhibit varying half-lives at the cell surface. The results highlight utility of the surface labeling/flow cytometry approach to quantitatively assess trafficking deficiencies associated with LQT2 mutations, to discern underlying mechanisms, and to report on interventions that rescue deficits in hERG surface expression.
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Affiliation(s)
- Scott A Kanner
- Doctoral Program in Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York, NY, United States
| | - Ananya Jain
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, NY, United States
| | - Henry M Colecraft
- Doctoral Program in Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York, NY, United States.,Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, NY, United States.,Department of Pharmacology, Columbia University College of Physicians and Surgeons, New York, NY, United States
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12
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Hover S, Foster B, Barr JN, Mankouri J. Viral dependence on cellular ion channels - an emerging anti-viral target? J Gen Virol 2017; 98:345-351. [PMID: 28113044 DOI: 10.1099/jgv.0.000712] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The broad range of cellular functions governed by ion channels represents an attractive target for viral manipulation. Indeed, modulation of host cell ion channel activity by viral proteins is being increasingly identified as an important virus-host interaction. Recent examples have demonstrated that virion entry, virus egress and the maintenance of a cellular environment conducive to virus persistence are, in part, dependent on virus manipulation of ion channel activity. Most excitingly, evidence has emerged that targeting ion channels pharmacologically can impede virus life cycles. Here, we discuss current examples of virus-ion channel interactions and the potential of targeting ion channel function as a new, pharmacologically safe and broad-ranging anti-viral therapeutic strategy.
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Affiliation(s)
- Samantha Hover
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Becky Foster
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - John N Barr
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Jamel Mankouri
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
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Foo B, Williamson B, Young JC, Lukacs G, Shrier A. hERG quality control and the long QT syndrome. J Physiol 2016; 594:2469-81. [PMID: 26718903 DOI: 10.1113/jp270531] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 12/07/2015] [Indexed: 11/08/2022] Open
Abstract
Long-QT syndrome type-2 (LQT2) is characterized by reduced functional expression of the human ether-à-go-go related (hERG) gene product, resulting in impaired cardiac repolarization and predisposition to fatal arrhythmia. Previous studies have implicated abnormal trafficking of misfolded hERG as the primary mechanism of LQT2, with misfolding being caused by mutations in the hERG gene (inherited) or drug treatment (acquired). More generally, environmental and metabolic stresses present a constant challenge to the folding of proteins, including hERG, and must be countered by robust protein quality control (QC) systems. Disposal of partially unfolded yet functional plasma membrane (PM) proteins by protein QC contributes to the loss-of-function phenotype in various conformational diseases including cystic fibrosis (CF) and long-QT syndrome type-2 (LQT2). The prevalent view has been that the loss of PM expression of hERG is attributed to biosynthetic block by endoplasmic reticulum (ER) QC pathways. However, there is a growing appreciation for protein QC pathways acting at post-ER cellular compartments, which may contribute to conformational disease pathogenesis. This article will provide a background on the structure and cellular trafficking of hERG as well as inherited and acquired LQT2. We will review previous work on hERG ER QC and introduce the more novel view that there is a significant peripheral QC at the PM and peripheral cellular compartments. Particular attention is drawn to the unique role of the peripheral QC system in acquired LQT2. Understanding the QC process and players may provide targets for therapeutic intervention in dealing with LQT2.
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Affiliation(s)
- Brian Foo
- Department of Physiology, McGill University, Montréal, Québec, Canada, H3G 1Y6
| | - Brittany Williamson
- Department of Biochemistry, McGill University, Montréal, Québec, Canada, H3G 1Y6
| | - Jason C Young
- Department of Biochemistry, McGill University, Montréal, Québec, Canada, H3G 1Y6
| | - Gergely Lukacs
- Department of Physiology, McGill University, Montréal, Québec, Canada, H3G 1Y6
| | - Alvin Shrier
- Department of Physiology, McGill University, Montréal, Québec, Canada, H3G 1Y6
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Guarnieri D, Muscetti O, Falanga A, Fusco S, Belli V, Perillo E, Battista E, Panzetta V, Galdiero S, Netti PA. Surface decoration with gH625-membranotropic peptides as a method to escape the endo-lysosomal compartment and reduce nanoparticle toxicity. NANOTECHNOLOGY 2015; 26:415101. [PMID: 26403519 DOI: 10.1088/0957-4484/26/41/415101] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The membranotropic peptide gH625 is able to transport different cargos (i.e., liposomes, quantum dots, polymeric nanoparticles) within and across cells in a very efficient manner. However, a clear understanding of the detailed uptake mechanism remains elusive. In this work, we investigate the journey of gH625-functionalized polystyrene nanoparticles in mouse-brain endothelial cells from their interaction with the cell membrane to their intracellular final destination. The aim is to elucidate how gH625 affects the behavior of the nanoparticles and their cytotoxic effect. The results indicate that the mechanism of translocation of gH625 dictates the fate of the nanoparticles, with a relevant impact on the nanotoxicological profile of positively charged nanoparticles.
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Affiliation(s)
- D Guarnieri
- Center for Advanced Biomaterials for health Care (CABHC), Istituto Italiano di Tecnologia, Largo Barsanti, Napoli, Italy and Interdisciplinary Research Centre on Biomaterials (CRIB), Napoli, Italy
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15
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Zhang KP, Yang BF, Li BX. Translational toxicology and rescue strategies of the hERG channel dysfunction: biochemical and molecular mechanistic aspects. Acta Pharmacol Sin 2014; 35:1473-84. [PMID: 25418379 PMCID: PMC4261120 DOI: 10.1038/aps.2014.101] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 08/20/2014] [Indexed: 01/08/2023] Open
Abstract
The human ether-à-go-go related gene (hERG) potassium channel is an obligatory anti-target for drug development on account of its essential role in cardiac repolarization and its close association with arrhythmia. Diverse drugs have been removed from the market owing to their inhibitory activity on the hERG channel and their contribution to acquired long QT syndrome (LQTS). Moreover, mutations that cause hERG channel dysfunction may induce congenital LQTS. Recently, an increasing number of biochemical and molecular mechanisms underlying hERG-associated LQTS have been reported. In fact, numerous potential biochemical and molecular rescue strategies are hidden within the biogenesis and regulating network. So far, rescue strategies of hERG channel dysfunction and LQTS mainly include activators, blockers, and molecules that interfere with specific links and other mechanisms. The aim of this review is to discuss the rescue strategies based on hERG channel toxicology from the biochemical and molecular perspectives.
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Affiliation(s)
- Kai-ping Zhang
- Department of Pharmacology, Harbin Medical University, Harbin, China
- The State-Province Key Laboratories of Biomedicine-Pharmaceutics of China (Key Laboratory of Cardiovascular Research, Ministry of Education), China
| | - Bao-feng Yang
- Department of Pharmacology, Harbin Medical University, Harbin, China
- The State-Province Key Laboratories of Biomedicine-Pharmaceutics of China (Key Laboratory of Cardiovascular Research, Ministry of Education), China
| | - Bao-xin Li
- Department of Pharmacology, Harbin Medical University, Harbin, China
- The State-Province Key Laboratories of Biomedicine-Pharmaceutics of China (Key Laboratory of Cardiovascular Research, Ministry of Education), China
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