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Arcangeli A, Iorio J, Duranti C. Targeting the hERG1 and β1 integrin complex for cancer treatment. Expert Opin Ther Targets 2024; 28:145-157. [PMID: 38372580 DOI: 10.1080/14728222.2024.2318449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 02/09/2024] [Indexed: 02/20/2024]
Abstract
INTRODUCTION Despite great advances, novel therapeutic targets and strategies are still needed, in particular for some carcinomas in the metastatic stage (breast cancer, colorectal cancer, pancreatic ductal adenocarcinoma and the clear cell renal carcinoma). Ion channels may be considered good cancer biomarkers and targets for antineoplastic therapy. These concepts are particularly relevant considering the hERG1 potassium channel as a novel target for antineoplastic therapy. AREAS COVERED A great deal of evidence demonstrates that hERG1 is aberrantly expressed in human cancers, in particular in aggressive carcinomas. A relevant cornerstone was the discovery that, in cancer cells, the channel is present in a very peculiar conformation, strictly bound to the β1 subunit of integrin receptors. The hERG1/β1 integrin complex does not occur in the heart. Starting from this evidence, we developed a novel single chain bispecific antibody (scDb-hERG1-β1), which specifically targets the hERG1/β1 integrin complex and exerts antineoplastic effects in preclinical experiments. EXPERT OPINION Since hERG1 blockade cannot be pursued for antineoplastic therapy due to the severe cardiac toxic effects (ventricular arrhythmias) that many hERG1 blockers exert, different strategies must be identified to specifically target hERG1 in cancer. The targeting of the hERG1/β1 integrin complex through the bispecific antibody scDb-hERG1-β1 can overcome such hindrances.
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Affiliation(s)
- Annarosa Arcangeli
- Department of Experimental and Clinical Medicine, Section of Internal Medicine, University of Florence, Firenze, Italy
- CSDC (Center for the Study of complex dynamics), University of Florence, Sesto Fiorentino (FI), Italy
- MCK Therapeutics srl, Pistoia (PT), Italy
| | - Jessica Iorio
- Department of Experimental and Clinical Medicine, Section of Internal Medicine, University of Florence, Firenze, Italy
| | - Claudia Duranti
- Department of Experimental and Clinical Medicine, Section of Internal Medicine, University of Florence, Firenze, Italy
- MCK Therapeutics srl, Pistoia (PT), Italy
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Hilgemann DW, Dai G, Collins A, Lariccia V, Magi S, Deisl C, Fine M. Lipid signaling to membrane proteins: From second messengers to membrane domains and adapter-free endocytosis. J Gen Physiol 2018; 150:211-224. [PMID: 29326133 PMCID: PMC5806671 DOI: 10.1085/jgp.201711875] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Hilgemann et al. explain how lipid signaling to membrane proteins involves a hierarchy of mechanisms from lipid binding to membrane domain coalescence. Lipids influence powerfully the function of ion channels and transporters in two well-documented ways. A few lipids act as bona fide second messengers by binding to specific sites that control channel and transporter gating. Other lipids act nonspecifically by modifying the physical environment of channels and transporters, in particular the protein–membrane interface. In this short review, we first consider lipid signaling from this traditional viewpoint, highlighting innumerable Journal of General Physiology publications that have contributed to our present understanding. We then switch to our own emerging view that much important lipid signaling occurs via the formation of membrane domains that influence the function of channels and transporters within them, promote selected protein–protein interactions, and control the turnover of surface membrane.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Gucan Dai
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
| | - Anthony Collins
- Saba University School of Medicine, The Bottom, Saba, Dutch Caribbean
| | - Vincenzo Lariccia
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche," Ancona, Italy
| | - Simona Magi
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche," Ancona, Italy
| | - Christine Deisl
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Michael Fine
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
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Li X, Anishkin A, Liu H, van Rossum DB, Chintapalli SV, Sassic JK, Gallegos D, Pivaroff-Ward K, Jegla T. Bimodal regulation of an Elk subfamily K+ channel by phosphatidylinositol 4,5-bisphosphate. ACTA ACUST UNITED AC 2016; 146:357-74. [PMID: 26503718 PMCID: PMC4621751 DOI: 10.1085/jgp.201511491] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PIP2 mediates the bimodal regulation of the EAG family K+ channel ELK1 to produce an overall inhibitory effect. Phosphatidylinositol 4,5-bisphosphate (PIP2) regulates Shaker K+ channels and voltage-gated Ca2+ channels in a bimodal fashion by inhibiting voltage activation while stabilizing open channels. Bimodal regulation is conserved in hyperpolarization-activated cyclic nucleotide–gated (HCN) channels, but voltage activation is enhanced while the open channel state is destabilized. The proposed sites of PIP2 regulation in these channels include the voltage-sensor domain (VSD) and conserved regions of the proximal cytoplasmic C terminus. Relatively little is known about PIP2 regulation of Ether-á-go-go (EAG) channels, a metazoan-specific family of K+ channels that includes three gene subfamilies, Eag (Kv10), Erg (Kv11), and Elk (Kv12). We examined PIP2 regulation of the Elk subfamily potassium channel human Elk1 to determine whether bimodal regulation is conserved within the EAG K+ channel family. Open-state stabilization by PIP2 has been observed in human Erg1, but the proposed site of regulation in the distal C terminus is not conserved among EAG family channels. We show that PIP2 strongly inhibits voltage activation of Elk1 but also stabilizes the open state. This stabilization produces slow deactivation and a mode shift in voltage gating after activation. However, removal of PIP2 has the net effect of enhancing Elk1 activation. R347 in the linker between the VSD and pore (S4–S5 linker) and R479 near the S6 activation gate are required for PIP2 to inhibit voltage activation. The ability of PIP2 to stabilize the open state also requires these residues, suggesting an overlap in sites central to the opposing effects of PIP2 on channel gating. Open-state stabilization in Elk1 requires the N-terminal eag domain (PAS domain + Cap), and PIP2-dependent stabilization is enhanced by a conserved basic residue (K5) in the Cap. Our data shows that PIP2 can bimodally regulate voltage gating in EAG family channels, as has been proposed for Shaker and HCN channels. PIP2 regulation appears fundamentally different for Elk and KCNQ channels, suggesting that, although both channel types can regulate action potential threshold in neurons, they are not functionally redundant.
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Affiliation(s)
- Xiaofan Li
- Department of Biology and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802 Department of Biology and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD 20742
| | - Hansi Liu
- Department of Biology and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802
| | - Damian B van Rossum
- Department of Biology and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802 Department of Biology and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802
| | - Sree V Chintapalli
- Arkansas Children's Nutrition Center and Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72202 Arkansas Children's Nutrition Center and Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72202
| | - Jessica K Sassic
- Department of Biology and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802
| | - David Gallegos
- Department of Biology and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802
| | - Kendra Pivaroff-Ward
- Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195
| | - Timothy Jegla
- Department of Biology and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802 Department of Biology and Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802
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WANG SEN, XU DI, WU TINGTING, GUO YAN, CHEN YANHONG, ZOU JIANGANG. β1-adrenergic regulation of rapid component of delayed rectifier K+ currents in guinea-pig cardiac myocytes. Mol Med Rep 2014; 9:1923-8. [DOI: 10.3892/mmr.2014.2035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 02/21/2014] [Indexed: 11/06/2022] Open
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Ma Q, Yu H, Lin J, Sun Y, Shen X, Ren L. Screening for cardiac HERG potassium channel interacting proteins using the yeast two-hybrid technique. Cell Biol Int 2013; 38:239-45. [PMID: 24154981 DOI: 10.1002/cbin.10196] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 09/25/2013] [Indexed: 12/12/2022]
Abstract
The human ERG protein (HERG or Kv 11.1) encoded by the human ether-a-go-go-related gene (herg) is the pore-forming subunit of the cardiac delayed rectifier potassium current (IKr) responsible for action potential (AP) repolarization. Mutations in HERG lead to long-QT syndrome, a major cause of arrhythmias. Protein-protein interactions are fundamental for ion channel trafficking, membrane localization, and functional modulation. To identify proteins involved in the regulation of the HERG channel, we conducted a yeast two-hybrid screen of a human heart cDNA library using the C-terminus or N-terminus of HERG as bait. Fifteen proteins were identified as HERG amino terminal (HERG-NT)-interacting proteins, including Caveolin-1 (a membrane scaffold protein with multiple interacting partners, including G-proteins, kinases and NOS), the zinc finger protein, FHL2 and PTPN12 (a non-receptor tyrosine phosphatase). Eight HERG carboxylic terminal (HERG-CT)-interacting proteins were also identified, including the NF-κB-interacting protein myotrophin, We have identified multiple potential interacting proteins that may regulate cardiac IKr through cytoskeletal interactions, G-protein modulation, phosphorylation and downstream second messenger and transcription cascades. These findings provide further insight into dynamic modulation of HERG under physiological conditions and arrhythmogenesis.
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Affiliation(s)
- Qingyan Ma
- Department of Cardiology, Guangdong Provincial Cardiovascular Institute, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, 510080, China
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Dai G, Peng C, Liu C, Varnum MD. Two structural components in CNGA3 support regulation of cone CNG channels by phosphoinositides. ACTA ACUST UNITED AC 2013; 141:413-30. [PMID: 23530136 PMCID: PMC3607822 DOI: 10.1085/jgp.201210944] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cyclic nucleotide-gated (CNG) channels in retinal photoreceptors play a crucial role in vertebrate phototransduction. The ligand sensitivity of photoreceptor CNG channels is adjusted during adaptation and in response to paracrine signals, but the mechanisms involved in channel regulation are only partly understood. Heteromeric cone CNGA3 (A3) + CNGB3 (B3) channels are inhibited by membrane phosphoinositides (PIP(n)), including phosphatidylinositol 3,4,5-triphosphate (PIP(3)) and phosphatidylinositol 4,5-bisphosphate (PIP(2)), demonstrating a decrease in apparent affinity for cyclic guanosine monophosphate (cGMP). Unlike homomeric A1 or A2 channels, A3-only channels paradoxically did not show a decrease in apparent affinity for cGMP after PIP(n) application. However, PIP(n) induced an ∼2.5-fold increase in cAMP efficacy for A3 channels. The PIP(n)-dependent change in cAMP efficacy was abolished by mutations in the C-terminal region (R643Q/R646Q) or by truncation distal to the cyclic nucleotide-binding domain (613X). In addition, A3-613X unmasked a threefold decrease in apparent cGMP affinity with PIP(n) application to homomeric channels, and this effect was dependent on conserved arginines within the N-terminal region of A3. Together, these results indicate that regulation of A3 subunits by phosphoinositides exhibits two separable components, which depend on structural elements within the N- and C-terminal regions, respectively. Furthermore, both N and C regulatory modules in A3 supported PIP(n) regulation of heteromeric A3+B3 channels. B3 subunits were not sufficient to confer PIP(n) sensitivity to heteromeric channels formed with PIP(n)-insensitive A subunits. Finally, channels formed by mixtures of PIP(n)-insensitive A3 subunits, having complementary mutations in N- and/or C-terminal regions, restored PIP(n) regulation, implying that intersubunit N-C interactions help control the phosphoinositide sensitivity of cone CNG channels.
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Affiliation(s)
- Gucan Dai
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164, USA
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Chun YS, Oh HG, Park MK, Cho H, Chung S. Cholesterol regulates HERG K+ channel activation by increasing phospholipase C β1 expression. Channels (Austin) 2013; 7:275-87. [PMID: 23793622 DOI: 10.4161/chan.25122] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Human ether-a-go-go-related gene (HERG) K(+) channel underlies the rapidly activating delayed rectifier K(+) conductance (IKr) during normal cardiac repolarization. Also, it may regulate excitability in many neuronal cells. Recently, we showed that enrichment of cell membrane with cholesterol inhibits HERG channels by reducing the levels of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] due to the activation of phospholipase C (PLC). In this study, we further explored the effect of cholesterol enrichment on HERG channel kinetics. When membrane cholesterol level was mildly increased in human embryonic kidney (HEK) 293 cells expressing HERG channel, the inactivation and deactivation kinetics of HERG current were not affected, but the activation rate was significantly decelerated at all voltages tested. The application of PtdIns(4,5)P2 or inhibitor for PLC prevented the effect of cholesterol enrichment, while the presence of antibody against PtdIns(4,5)P2 in pipette solution mimicked the effect of cholesterol enrichment. These results indicate that the effect of cholesterol enrichment on HERG channel is due to the depletion of PtdIns(4,5)P2. We also found that cholesterol enrichment significantly increases the expression of β1 and β3 isoforms of PLC (PLCβ1, PLCβ3) in the membrane. Since the effects of cholesterol enrichment on HERG channel were prevented by inhibiting transcription or by inhibiting PLCβ1 expression, we conclude that increased PLCβ1 expression leads to the deceleration of HERG channel activation rate via downregulation of PtdIns(4,5)P2. These results confirm a crosstalk between two plasma membrane-enriched lipids, cholesterol and PtdIns(4,5)P2, in the regulation of HERG channels.
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Affiliation(s)
- Yoon Sun Chun
- Department of Physiology; Samsung Biomedical Research Institute; Sungkyunkwan University School of Medicine; Suwon, South Korea
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Cooley N, Ouyang K, McMullen JR, Kiriazis H, Sheikh F, Wu W, Mu Y, Du XJ, Chen J, Woodcock EA. No contribution of IP3-R(2) to disease phenotype in models of dilated cardiomyopathy or pressure overload hypertrophy. Circ Heart Fail 2012; 6:318-25. [PMID: 23258573 DOI: 10.1161/circheartfailure.112.972158] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND We investigated the contribution of inositol(1,4,5)-trisphosphate (Ins(1,4,5)P3 [IP3]) receptors (IP3-R) to disease progression in mouse models of dilated cardiomyopathy (DCM) and pressure overload hypertrophy. Mice expressing mammalian sterile 20-like kinase and dominant-negative phosphatidylinositol-3-kinase in heart (Mst1×dn-PI3K-2Tg; DCM-2Tg) develop severe DCM and conduction block, associated with increased expression of type 2 IP3-R (IP3-R(2)) and heightened generation of Ins(1,4,5)P3. Similar increases in Ins(1,4,5)P3 and IP3-R(2) are caused by transverse aortic constriction. METHODS AND RESULTS To evaluate the contribution of IP3-R(2) to disease progression, the DCM-2Tg mice were further crossed with mice in which the type 2 IP3-R (IP3-R(2)-/-) had been deleted (DCM-2Tg×IP3-R(2)-/-) and transverse aortic constriction was performed on IP3-R(2)-/- mice. Hearts from DCM-2Tg mice and DCM-2Tg×IP3-R(2)-/- were similar in terms of chamber dilatation, atrial enlargement, and ventricular wall thinning. Electrophysiological changes were also similar in the DCM-2Tg mice, with and without IP3-R(2). Deletion of IP3-R(2) did not alter the progression of heart failure, because DCM-2Tg mice with and without IP3-R(2) had similarly reduced contractility, increased lung congestion, and atrial thrombus, and both strains died between 10 and 12 weeks of age. Loss of IP3-R(2) did not alter the progression of hypertrophy after transverse aortic constriction. CONCLUSIONS We conclude that IP3-R(2) do not contribute to the progression of DCM or pressure overload hypertrophy, despite increased expression and heightened generation of the ligand, Ins(1,4,5)P3.
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Affiliation(s)
- Nicola Cooley
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
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Kruse M, Hammond GRV, Hille B. Regulation of voltage-gated potassium channels by PI(4,5)P2. ACTA ACUST UNITED AC 2012; 140:189-205. [PMID: 22851677 PMCID: PMC3409096 DOI: 10.1085/jgp.201210806] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) regulates activities of numerous ion channels including inwardly rectifying potassium (Kir) channels, KCNQ, TRP, and voltage-gated calcium channels. Several studies suggest that voltage-gated potassium (KV) channels might be regulated by PI(4,5)P2. Wide expression of KV channels in different cells suggests that such regulation could have broad physiological consequences. To study regulation of KV channels by PI(4,5)P2, we have coexpressed several of them in tsA-201 cells with a G protein–coupled receptor (M1R), a voltage-sensitive lipid 5-phosphatase (Dr-VSP), or an engineered fusion protein carrying both lipid 4-phosphatase and 5-phosphatase activity (pseudojanin). These tools deplete PI(4,5)P2 with application of muscarinic agonists, depolarization, or rapamycin, respectively. PI(4,5)P2 at the plasma membrane was monitored by Förster resonance energy transfer (FRET) from PH probes of PLCδ1 simultaneously with whole-cell recordings. Activation of Dr-VSP or recruitment of pseudojanin inhibited KV7.1, KV7.2/7.3, and Kir2.1 channel current by 90–95%. Activation of M1R inhibited KV7.2/7.3 current similarly. With these tools, we tested for potential PI(4,5)P2 regulation of activity of KV1.1/KVβ1.1, KV1.3, KV1.4, and KV1.5/KVβ1.3, KV2.1, KV3.4, KV4.2, KV4.3 (with different KChIPs and DPP6-s), and hERG/KCNE2. Interestingly, we found a substantial removal of inactivation for KV1.1/KVβ1.1 and KV3.4, resulting in up-regulation of current density upon activation of M1R but no changes in activity upon activating only VSP or pseudojanin. The other channels tested except possibly hERG showed no alteration in activity in any of the assays we used. In conclusion, a depletion of PI(4,5)P2 at the plasma membrane by enzymes does not seem to influence activity of most tested KV channels, whereas it does strongly inhibit members of the KV7 and Kir families.
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Affiliation(s)
- Martin Kruse
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
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Wondergem R, Graves BM, Li C, Williams DL. Lipopolysaccharide prolongs action potential duration in HL-1 mouse cardiomyocytes. Am J Physiol Cell Physiol 2012; 303:C825-33. [PMID: 22895260 DOI: 10.1152/ajpcell.00173.2012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sepsis has deleterious effects on cardiac function including reduced contractility. We have shown previously that lipopolysaccharides (LPS) directly affect HL-1 cardiac myocytes by inhibiting Ca(2+) regulation and by impairing pacemaker "funny" current, I(f). We now explore further cellular mechanisms whereby LPS inhibits excitability in HL-1 cells. LPS (1 μg/ml) derived from Salmonella enteritidis decreased rate of firing of spontaneous action potentials in HL-1 cells, and it increased their pacemaker potential durations and decreased their rates of depolarization, all measured by whole cell current clamp. LPS also increased action potential durations and decreased their amplitude in cells paced at 1 Hz with 0.1 nA, and 20 min were necessary for maximal effect. LPS decreased the amplitude of a rapidly inactivating inward current attributed to Na(+) and of an outward current attributed to K(+); both were measured by whole cell voltage clamp. The K(+) currents displayed a resurgent outward tail current, which is characteristic of the rapid delayed-rectifier K(+) current, I(Kr). LPS accordingly reduced outward currents measured with pipette Cs(+) substituted for K(+) to isolate I(Kr). E-4031 (1 μM) markedly inhibited I(Kr) in HL-1 cells and also increased action potential duration; however, the direct effects of E-4031 occurred minutes faster than the slow effects of LPS. We conclude that LPS increases action potential duration in HL-1 mouse cardiomyocytes by inhibition of I(Kr) and decreases their rate of firing by inhibition of I(Na.) This protracted time course points toward an intermediary metabolic event, which either decreases available mouse ether-a-go-go (mERG) and Na(+) channels or potentiates their inactivation.
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Affiliation(s)
- Robert Wondergem
- Department of Biomedical Science, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee 37614-1708, USA.
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Vandenberg JI, Perry MD, Perrin MJ, Mann SA, Ke Y, Hill AP. hERG K+ Channels: Structure, Function, and Clinical Significance. Physiol Rev 2012; 92:1393-478. [DOI: 10.1152/physrev.00036.2011] [Citation(s) in RCA: 463] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The human ether-a-go-go related gene (hERG) encodes the pore-forming subunit of the rapid component of the delayed rectifier K+ channel, Kv11.1, which are expressed in the heart, various brain regions, smooth muscle cells, endocrine cells, and a wide range of tumor cell lines. However, it is the role that Kv11.1 channels play in the heart that has been best characterized, for two main reasons. First, it is the gene product involved in chromosome 7-associated long QT syndrome (LQTS), an inherited disorder associated with a markedly increased risk of ventricular arrhythmias and sudden cardiac death. Second, blockade of Kv11.1, by a wide range of prescription medications, causes drug-induced QT prolongation with an increase in risk of sudden cardiac arrest. In the first part of this review, the properties of Kv11.1 channels, including biogenesis, trafficking, gating, and pharmacology are discussed, while the second part focuses on the pathophysiology of Kv11.1 channels.
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Affiliation(s)
- Jamie I. Vandenberg
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Matthew D. Perry
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Mark J. Perrin
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Stefan A. Mann
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Ying Ke
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Adam P. Hill
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
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Pahlavan S, Oberhofer M, Sauer B, Ruppenthal S, Tian Q, Scholz A, Kaestner L, Lipp P. Gαq and Gα11 contribute to the maintenance of cellular electrophysiology and Ca2+ handling in ventricular cardiomyocytes. Cardiovasc Res 2012; 95:48-58. [DOI: 10.1093/cvr/cvs162] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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Abstract
Phosphoinositides (PIs), a family of phosphorylated derivatives of the membrane lipid phosphatidylinositol, are established regulators of multiple cellular functions. An increasing amount of evidence has highlighted potential links between PI-mediated signaling pathways and the etiology of many human diseases, including cardiovascular pathologies. This chapter will provide a detailed overview of the peculiar functions of the major cardiovascular PIs in the pathogenesis of atherosclerosis, heart failure, and arrhythmias.
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Affiliation(s)
- Alessandra Ghigo
- Department of Genetics, Biology and Biochemistry, University of Torino, Molecular Biotechnology Center, Italy
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Zheng F, Li H, Liang K, Du Y, Guo D, Huang S. Imatinib has the potential to exert its antileukemia effects by down-regulating hERG1 K+ channels in chronic myelogenous leukemia. Med Oncol 2011; 29:2127-35. [PMID: 22161019 DOI: 10.1007/s12032-011-0102-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 10/27/2011] [Indexed: 11/25/2022]
Abstract
Imatinib is a powerful protein tyrosine kinase (PTK) inhibitor that specifically targets BCR-ABL, KIT, and PDGFR kinases, has become the current first-line therapy for all newly diagnosed chronic myeloid leukemia (CML). Beside PTKs, PTK inhibitors alter the activity of a large number of voltage-dependent ion channels. hERG1 K(+) channels are highly expressed in leukemia cells and appear of exceptional importance in favoring leukemogenesis. The present study explored a possible regulatory effect of imatinib upon hERG1 K(+) channels as a means to uncover new molecular events involved in the antileukemic activity of this PTK inhibitor in CML. The results demonstrated that hERG1 was highly detected in K562 cells and primary CML cells, and down-regulated by imatinib at mRNA and protein levels. Furthermore, imatinib markedly reduced hERG currents in HEK293T-hERG cells, this effect was accompanied by inhibition of CML cell proliferation and apoptosis, as well as suppression of vascular endothelial growth factor (VEGF) secretion. Moreover, these antileukemia effects of imatinib were potentiated by E-4031, a specific hERG1 inhibitor. Together, these results provide evidence of a novel potential molecular mechanism of antileukemic activities by imatinib which, independent of targeting tyrosine kinase, highlight hERG1 K(+) channels as a therapeutic target for CML treatment.
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Affiliation(s)
- Fang Zheng
- Center for Stem Cell Research and Application, Institute of Hematology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Road 1277, Wuhan 430022, People's Republic of China
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Flynn GE, Zagotta WN. Molecular mechanism underlying phosphatidylinositol 4,5-bisphosphate-induced inhibition of SpIH channels. J Biol Chem 2011; 286:15535-42. [PMID: 21383006 PMCID: PMC3083228 DOI: 10.1074/jbc.m110.214650] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Many ion channels have been shown to be regulated by the membrane signaling phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2). Here, we demonstrate that the binding of PIP2 to SpIH, a sea urchin hyperpolarization-activated cyclic nucleotide-gated ion channel (HCN), has a dual effect: potentiation and inhibition. The potentiation is observed as a shift in the voltage dependence of activation to more depolarized voltages. The inhibition is observed as a reduction in the currents elicited by the partial agonist cGMP. These two effects were separable and arose from PIP2 binding to two different regions. Deletion of the C-terminal region of SpIH removed PIP2-induced inhibition but not the PIP2-induced shift in voltage dependence. Mutating key positively charged amino acids in the C-terminal region adjacent to the membrane selectively disrupted PIP2-induced inhibition, suggesting a direct interaction between PIP2 in the membrane and amino acids in the C-terminal region that stabilizes the closed state relative to the open state in HCN channels.
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Affiliation(s)
- Galen E Flynn
- Department of Physiology and Biophysics, Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195-7290, USA
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16
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Rodriguez N, Amarouch MY, Montnach J, Piron J, Labro AJ, Charpentier F, Mérot J, Baró I, Loussouarn G. Phosphatidylinositol-4,5-bisphosphate (PIP(2)) stabilizes the open pore conformation of the Kv11.1 (hERG) channel. Biophys J 2010; 99:1110-8. [PMID: 20712994 DOI: 10.1016/j.bpj.2010.06.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Revised: 05/28/2010] [Accepted: 06/01/2010] [Indexed: 01/30/2023] Open
Abstract
Phosphatidylinositol-4,5-bisphosphate (PIP(2)) is a phospholipid that has been shown to modulate several ion channels, including some voltage-gated channels like Kv11.1 (hERG). From a biophysical perspective, the mechanisms underlying this regulation are not well characterized. From a physiological perspective, it is critical to establish whether the PIP(2) effect is within the physiological concentration range. Using the giant-patch configuration of the patch-clamp technique on COS-7 cells expressing hERG, we confirmed the activating effect of PIP(2). PIP(2) increased the hERG maximal current and concomitantly slowed deactivation. Regarding the molecular mechanism, these increased amplitude and slowed deactivation suggest that PIP(2) stabilizes the channel open state, as it does in KCNE1-KCNQ1. We used kinetic models of hERG to simulate the effects of the phosphoinositide. Simulations strengthened the hypothesis that PIP(2) is more likely stabilizing the channel open state than affecting the voltage sensors. From the physiological aspect, we established that the sensitivity of hERG to PIP(2) comes close to that of KCNE1-KCNQ1 channels, which lies in the range of physiological PIP(2) variations.
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Affiliation(s)
- Nicolas Rodriguez
- Institut National de la Santé et de la Recherche Médicale, Nantes, France
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17
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Logothetis DE, Petrou VI, Adney SK, Mahajan R. Channelopathies linked to plasma membrane phosphoinositides. Pflugers Arch 2010; 460:321-41. [PMID: 20396900 PMCID: PMC4040125 DOI: 10.1007/s00424-010-0828-y] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 03/11/2010] [Accepted: 03/13/2010] [Indexed: 02/07/2023]
Abstract
The plasma membrane phosphoinositide phosphatidylinositol 4,5-bisphosphate (PIP2) controls the activity of most ion channels tested thus far through direct electrostatic interactions. Mutations in channel proteins that change their apparent affinity to PIP2 can lead to channelopathies. Given the fundamental role that membrane phosphoinositides play in regulating channel activity, it is surprising that only a small number of channelopathies have been linked to phosphoinositides. This review proposes that for channels whose activity is PIP2-dependent and for which mutations can lead to channelopathies, the possibility that the mutations alter channel-PIP2 interactions ought to be tested. Similarly, diseases that are linked to disorders of the phosphoinositide pathway result in altered PIP2 levels. In such cases, it is proposed that the possibility for a concomitant dysregulation of channel activity also ought to be tested. The ever-growing list of ion channels whose activity depends on interactions with PIP2 promises to provide a mechanism by which defects on either the channel protein or the phosphoinositide levels can lead to disease.
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Affiliation(s)
- Diomedes E Logothetis
- Department of Physiology and Biophysics, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA.
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18
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Role of ERG1 isoforms in modulation of ERG1 channel trafficking and function. Pflugers Arch 2010; 460:803-12. [DOI: 10.1007/s00424-010-0855-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 06/13/2010] [Accepted: 06/14/2010] [Indexed: 01/31/2023]
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19
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Abstract
Phosphoinositides play an important role in both abiotic and biotic signalling in plants. The signalling cascade may include the production of second messengers by hydrolysis of PtdIns(4,5)P2. However, increasingly, PtdIns(4,5)P2 itself is shown to mediate signalling by regulating target proteins. The present mini-review summarizes the experimentally demonstrated effects of PtdIns(4,5)P2 on plant K+ channels and examines their structure for candidate sites of direct PtdIns(4,5)P2–protein interaction.
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20
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Physical and Functional Interaction between Integrins and hERG1 Channels in Cancer Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 674:55-67. [DOI: 10.1007/978-1-4419-6066-5_6] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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21
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Ramström C, Chapman H, Viitanen T, Afrasiabi E, Fox H, Kivelä J, Soini S, Korhonen L, Lindholm D, Pasternack M, Törnquist K. Regulation of HERG (KCNH2) potassium channel surface expression by diacylglycerol. Cell Mol Life Sci 2010; 67:157-69. [PMID: 19859662 PMCID: PMC11115617 DOI: 10.1007/s00018-009-0176-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 09/30/2009] [Accepted: 10/06/2009] [Indexed: 01/08/2023]
Abstract
The HERG (KCNH2) channel is a voltage-sensitive potassium channel mainly expressed in cardiac tissue, but has also been identified in other tissues like neuronal and smooth muscle tissue, and in various tumours and tumour cell lines. The function of HERG has been extensively studied, but it is still not clear what mechanisms regulate the surface expression of the channel. In the present report, using human embryonic kidney cells stably expressing HERG, we show that diacylglycerol potently inhibits the HERG current. This is mediated by a protein kinase C-evoked endocytosis of the channel protein, and is dependent on the dynein-dynamin complex. The HERG protein was found to be located only in early endosomes and not lysosomes. Thus, diacylglycerol is an important lipid participating in the regulation of HERG surface expression and function.
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Affiliation(s)
- Cia Ramström
- Department of Biology, Åbo Akademi University, 20520 Turku, Finland
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki, 00290 Helsinki, Finland
| | - Hugh Chapman
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki, 00290 Helsinki, Finland
| | - Tero Viitanen
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki, 00290 Helsinki, Finland
| | - Emad Afrasiabi
- Department of Biology, Åbo Akademi University, 20520 Turku, Finland
| | - Heli Fox
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki, 00290 Helsinki, Finland
| | - Johanna Kivelä
- Department of Pharmacology and Clinical Pharmacology, University of Turku, 20520 Turku, Finland
| | - Sanna Soini
- Department of Pharmacology and Clinical Pharmacology, University of Turku, 20520 Turku, Finland
| | - Laura Korhonen
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki, 00290 Helsinki, Finland
| | - Dan Lindholm
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki, 00290 Helsinki, Finland
| | - Michael Pasternack
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki, 00290 Helsinki, Finland
| | - Kid Törnquist
- Department of Biology, Åbo Akademi University, 20520 Turku, Finland
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki, 00290 Helsinki, Finland
- Department of Biology, Åbo Akademi University, BioCity, Tykistökatu 6, 20520 Turku, Finland
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22
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Erg K+ currents modulate excitability in mouse mitral/tufted neurons. Pflugers Arch 2009; 459:55-70. [DOI: 10.1007/s00424-009-0709-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 06/13/2009] [Accepted: 07/30/2009] [Indexed: 10/20/2022]
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23
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Wang S, Xu DJ, Cai JB, Huang YZ, Zou JG, Cao KJ. Rapid component I(Kr) of cardiac delayed rectifier potassium currents in guinea-pig is inhibited by alpha(1)-adrenoreceptor activation via protein kinase A and protein kinase C-dependent pathways. Eur J Pharmacol 2009; 608:1-6. [PMID: 19233158 DOI: 10.1016/j.ejphar.2009.02.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2008] [Revised: 02/06/2009] [Accepted: 02/12/2009] [Indexed: 11/29/2022]
Abstract
Ventricular tachyarrhythmias are often precipitated by physical or emotional stress, indicating a link between increased adrenergic stimulation and cardiac ion channel activity. Human ether-a-go-go related gene (hERG) potassium channels conduct the rapid component of delayed rectifier potassium current, I(kr), a crucial component for action potential repolarization. To evaluate the correlation between increased alpha(1)-adrenergic activity and the rapid component of cardiac I(kr), whole-cell patch-clamp recording was performed in isolated guinea-pig ventricular myocytes. Stimulation of alpha(1)-adrenoceptors using phenylephrine (0.1 nM-100 microM) reduced I(kr) current in a dose-dependent manner at 37 degrees C. Phenylephrine (0.1 microM) reduced I(kr) current to 66.83+/-3.16%. Chelerythrine (1 microM), a specific inhibitor of protein kinase C (PKC) completely inhibited the changes in I(kr) trigged by 0.1 microM phenylephrine. KT5720 (2.5 microM), a specific inhibitor of protein kinase A (PKA) partially inhibited the current decrease induced by 0.1 microM phenylephrine. Both chelerythrine and KT5720 drastically reduced the phenylephrine-induced effects, indicating possible involvement of PKC and PKA in the alpha(1)-adrenergic inhibition of I(kr). Our data suggest a link between I(kr) and the alpha(1)-adrenoceptor, involving activation of PKC and PKA in arrhythmogenesis.
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Affiliation(s)
- Sen Wang
- Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China
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24
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Lin J, Lin S, Choy PC, Shen X, Deng C, Kuang S, Wu J, Xu W. The regulation of the cardiac potassium channel (HERG) by caveolin-1. Biochem Cell Biol 2008; 86:405-15. [PMID: 18923542 DOI: 10.1139/o08-118] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Protein-protein interaction plays a key role in the regulation of biological processes. The human potassium (HERG) channel is encoded by the ether-à-go-go-related gene (herg), and its activity may be regulated by association with other cellular proteins. To identify cellular proteins that might play a role in the regulation of the HERG channel, we screened a human heart cDNA library with the N terminus of HERG using a yeast 2-hybrid system, and identified caveolin-1 as a potential HERG partner. The interaction between these 2 proteins was confirmed by coimmunoprecipitation assay, and their overlapping subcellular localization was demonstrated by fluorescence immunocytochemistry. The physiologic implication of the protein-protein interaction was studied in whole-cell patch-clamp electrophysiology experiments. A significant increase in HERG current amplitude and a faster deactivation of tail current were observed in HEK293/HERG cells in a membrane lipid rafts disruption model and caveolin-1 knocked down cells by RNA interference. Alternatively, when caveolin-1 was overexpressed, the HERG current amplitude was significantly reduced and the tail current was deactivated more slowly. Taken together, these data indicate that HERG channels interact with caveolin-1 and are negatively regulated by this interaction. The finding from this study clearly demonstrates the regulatory role of caveolin-1 on HERG channels, and may help to understand biochemical events leading to arrhythmogenesis in the long QT syndrome in cardiac patients.
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Affiliation(s)
- Jijin Lin
- Department of Cardiology, Guangdong Provincial People's Hospital, Guangdong Provincial Cardiovascular Institute, 96 Dongchuan Road, Guangzhou 510080, China
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25
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Zhao FL, Herness S. Resynthesis of phosphatidylinositol 4,5-bisphosphate mediates adaptation of the caffeine response in rat taste receptor cells. J Physiol 2008; 587:363-77. [PMID: 19047199 DOI: 10.1113/jphysiol.2008.165167] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Caffeine, a prototypic bitter stimulus, produces several physiological actions on taste receptor cells that include inhibition of KIR and KV potassium currents and elevations of intracellular calcium. These responses display adaptation, i.e. their magnitude diminishes in the sustained presence of the stimulus. Levels of the membrane lipid phosphatidylinositol-4,5-bisphosphate (PIP2) are well known to modulate many potassium channels, activating the channel by stabilizing its open state. Here we investigate a putative relationship of KIR and KV with PIP2 levels hypothesizing that inhibition of these currents by caffeine might be allayed by PIP2 resynthesis. Using standard patch-clamp techniques, recordings of either potassium current from rat posterior taste receptor cells produced essentially parallel results when PIP2 levels were manipulated pharmacologically. Increasing PIP2 levels by blocking phosphoinositide-3 kinase with wortmannin or LY294002, or by blocking phospholipase C with U73122 all significantly increased the incidence of adaptation for both KIR and KV. Conversely, lowering PIP2 synthesis by blocking PI4K or using the PIP2 scavengers polylysine or bovine serum albumin reduced the incidence of adaptation. Adaptation could be modulated by activation of protein kinase C but not calcium calmodulin kinase. Collectively, these data support two highly novel conclusions: potassium currents in taste receptor cells are significantly modulated by PIP2 levels and PIP2 resynthesis may play a central role in the gustatory adaptation process at the primary receptor cell level.
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Affiliation(s)
- Fang-Li Zhao
- College of Dentistry, Ohio State University, Columbus, OH 43210, USA
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26
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Potet F, Petersen CI, Boutaud O, Shuai W, Stepanovic SZ, Balser JR, Kupershmidt S. Genetic screening in C. elegans identifies rho-GTPase activating protein 6 as novel HERG regulator. J Mol Cell Cardiol 2008; 46:257-67. [PMID: 19038263 DOI: 10.1016/j.yjmcc.2008.10.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 09/17/2008] [Accepted: 10/10/2008] [Indexed: 10/21/2022]
Abstract
The human ether-a-go-go related gene (HERG) constitutes the pore forming subunit of I(Kr), a K(+) current involved in repolarization of the cardiac action potential. While mutations in HERG predispose patients to cardiac arrhythmias (Long QT syndrome; LQTS), altered function of HERG regulators are undoubtedly LQTS risk factors. We have combined RNA interference with behavioral screening in Caenorhabditis elegans to detect genes that influence function of the HERG homolog, UNC-103. One such gene encodes the worm ortholog of the rho-GTPase activating protein 6 (ARHGAP6). In addition to its GAP function, ARHGAP6 induces cytoskeletal rearrangements and activates phospholipase C (PLC). Here we show that I(Kr) recorded in cells co-expressing HERG and ARHGAP6 was decreased by 43% compared to HERG alone. Biochemical measurements of cell-surface associated HERG revealed that ARHGAP6 reduced membrane expression of HERG by 35%, which correlates well with the reduction in current. In an atrial myocyte cell line, suppression of endogenous ARHGAP6 by virally transduced shRNA led to a 53% enhancement of I(Kr). ARHGAP6 effects were maintained when we introduced a dominant negative rho-GTPase, or ARHGAP6 devoid of rhoGAP function, indicating ARHGAP6 regulation of HERG is independent of rho activation. However, ARHGAP6 lost effectiveness when PLC was inhibited. We further determined that ARHGAP6 effects are mediated by a consensus SH3 binding domain within the C-terminus of HERG, although stable ARHGAP6-HERG complexes were not observed. These data link a rhoGAP-activated PLC pathway to HERG membrane expression and implicate this family of proteins as candidate genes in disorders involving HERG.
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Affiliation(s)
- Franck Potet
- Department of Anesthesiology, Vanderbilt University, Nashville, TN 37232, USA
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27
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Abstract
Arrhythmias arise from a complex interaction between structural changes in the myocardium and changes in cellular electrophysiology. Electrophysiological balance requires precise control of sarcolemmal ion channels and exchangers, many of which are regulated by phospholipid, phosphatidylinositol(4,5)bisphosphate. Phosphatidylinositol(4,5)bisphosphate is the immediate precursor of inositol(1,4,5)trisphosphate, a regulator of intracellular Ca2+ signalling and, therefore, a potential contributor to arrhythmogenesis by altering Ca2+ homeostasis. The aim of the present review is to outline current evidence that this signalling pathway can be a player in the initiation or maintenance of arrhythmias.
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Affiliation(s)
- Elizabeth A Woodcock
- Molecular Cardiology Laboratory, Baker IDI Heart and Diabetes Institute, PO Box 6492, St Kilda Road Central, Melbourne, 8008 Victoria, Australia.
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28
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Lin J, Lin S, Yu X, Choy PC, Shen X, Deng C, Kuang S, Wu J. The four and a half LIM domain protein 2 interacts with and regulates the HERG channel. FEBS J 2008; 275:4531-9. [DOI: 10.1111/j.1742-4658.2008.06596.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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29
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Voltage-gated K Channels - III. Biophys J 2008. [DOI: 10.1016/s0006-3495(08)79075-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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30
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Peroz D, Rodriguez N, Choveau F, Baró I, Mérot J, Loussouarn G. Kv7.1 (KCNQ1) properties and channelopathies. J Physiol 2008; 586:1785-9. [PMID: 18174212 DOI: 10.1113/jphysiol.2007.148254] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
KCNQ1 is the pore-forming subunit of a channel complex whose expression and function have been rather well characterized in the heart. Almost 300 mutations of KCNQ1 have been identified in patients and a vast majority of the described mutations are linked to the long QT syndrome. Only a few mutations are linked to other pathologies such as atrial fibrillation and the short QT syndrome. However, a considerable amount of work remains to be done to get a clear picture of the molecular mechanisms responsible for the pathogenesis related to each mutation. The present review gives three examples of recent studies towards this goal and illustrates the diversity of the molecular mechanisms involved.
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31
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Gamper N, Shapiro MS. Regulation of ion transport proteins by membrane phosphoinositides. Nat Rev Neurosci 2007; 8:921-34. [DOI: 10.1038/nrn2257] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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32
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Acetylcholine-induced Ca2+ oscillations are modulated by a Ca2+ regulation of InsP3R2 in rat portal vein myocytes. Pflugers Arch 2007; 456:277-83. [PMID: 18026983 DOI: 10.1007/s00424-007-0379-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2007] [Revised: 10/20/2007] [Accepted: 10/25/2007] [Indexed: 12/14/2022]
Abstract
Oscillations of cytosolic Ca2+ levels are believed to have important roles in various metabolic and signalling processes in many cell types. Previously, we have demonstrated that acetylcholine (ACh) evokes Ca2+ oscillations in vascular myocytes expressing InsP3R1 and InsP3R2, whereas transient responses are activated in vascular myocytes expressing InsP3R1 alone. The molecular mechanisms underlying oscillations remain to be described in these native smooth muscle cells. Two major hypotheses are proposed to explain this crucial signalling activity: (1) Ca2+ oscillations are activated by InsP3 oscillations; and (2) Ca2+ oscillations depend on the regulation of the InsP3R by both InsP3 and Ca2+. In the present study, we used a fluorescent InsP3 biosensor and revealed that ACh induced a transient InsP3 production in all myocytes. Moreover, steady concentrations of 3F-InsP3, a poorly hydrolysable analogue of InsP3, and pharmacological activation of PLC evoked Ca2+ oscillations. Increasing cytosolic Ca2+ inhibited the ACh-induced calcium oscillations but not the transient responses and strongly reduced the 3F-InsP3-evoked Ca2+ response in oscillating cells but not in non-oscillating cells. These results suggest that, in native vascular myocytes, ACh-induced InsP3 production is transient and Ca2+ oscillations depend on a Ca2+ modulation of InsP3R2.
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