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Chakraborty A, Paynter A, Szendrey M, Cornwell JD, Li W, Guo J, Yang T, Du Y, Wang T, Zhang S. Ubiquitination is involved in PKC-mediated degradation of cell surface Kv1.5 channels. J Biol Chem 2024; 300:107483. [PMID: 38897569 PMCID: PMC11301065 DOI: 10.1016/j.jbc.2024.107483] [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: 02/09/2024] [Revised: 05/30/2024] [Accepted: 06/12/2024] [Indexed: 06/21/2024] Open
Abstract
The voltage-gated Kv1.5 potassium channel, conducting the ultra-rapid delayed rectifier K+ current (IKur) in human cells, plays important roles in the repolarization of atrial action potentials and regulation of the vascular tone. We previously reported that activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate (PMA) induces endocytic degradation of cell-surface Kv1.5 channels, and a point mutation removing the phosphorylation site, T15A, in the N terminus of Kv1.5 abolished the PMA-effect. In the present study, using mutagenesis, patch clamp recording, Western blot analysis, and immunocytochemical staining, we demonstrate that ubiquitination is involved in the PMA-mediated degradation of mature Kv1.5 channels. Since the expression of the Kv1.4 channel is unaffected by PMA treatment, we swapped the N- and/or C-termini between Kv1.5 and Kv1.4. We found that the N-terminus alone did not but both N- and C-termini of Kv1.5 did confer PMA sensitivity to mature Kv1.4 channels, suggesting the involvement of Kv1.5 C-terminus in the channel ubiquitination. Removal of each of the potential ubiquitination residue Lysine at position 536, 565, and 591 by Arginine substitution (K536R, K565R, and K591R) had little effect, but removal of all three Lysine residues with Arginine substitution (3K-R) partially reduced PMA-mediated Kv1.5 degradation. Furthermore, removing the cysteine residue at position 604 by Serine substitution (C604S) drastically reduced PMA-induced channel degradation. Removal of the three Lysines and Cys604 with a quadruple mutation (3K-R/C604S) or a truncation mutation (Δ536) completely abolished the PKC activation-mediated degradation of Kv1.5 channels. These results provide mechanistic insight into PKC activation-mediated Kv1.5 degradation.
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Affiliation(s)
- Ananya Chakraborty
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - Amanda Paynter
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - Mark Szendrey
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - James D Cornwell
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - Wentao Li
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - Jun Guo
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - Tonghua Yang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - Yuan Du
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - Tingzhong Wang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada
| | - Shetuan Zhang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada.
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Milton AO, Wang T, Li W, Guo J, Zhang S. Mechanical stretch increases Kv1.5 current through an interaction between the S1-S2 linker and N-terminus of the channel. J Biol Chem 2020; 295:4723-4732. [PMID: 32122972 DOI: 10.1074/jbc.ra119.011302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 02/27/2020] [Indexed: 11/06/2022] Open
Abstract
The voltage-gated potassium channel Kv1.5 plays important roles in atrial repolarization and regulation of vascular tone. In the present study, we investigated the effects of mechanical stretch on Kv1.5 channels. We induced mechanical stretch by centrifuging or culturing Kv1.5-expressing HEK 293 cells and neonatal rat ventricular myocytes in low osmolarity (LO) medium and then recorded Kv1.5 current (IKv1.5) in a normal, isotonic solution. We observed that mechanical stretch increased IKv1.5, and this increase required the intact, long, proline-rich extracellular S1-S2 linker of the Kv1.5 channel. The low osmolarity-induced IKv1.5 increase also required an intact intracellular N terminus, which contains the binding motif for endogenous Src tyrosine kinase that constitutively inhibits IKv1.5 Disrupting the Src-binding motif of Kv1.5 through N-terminal truncation or mutagenesis abolished the mechanical stretch-mediated increase in IKv1.5 Our results further showed that the extracellular S1-S2 linker of Kv1.5 communicates with the intracellular N terminus. Although the S1-S2 linker of WT Kv1.5 could be cleaved by extracellularly applied proteinase K (PK), an N-terminal truncation up to amino acid residue 209 altered the conformation of the S1-S2 linker and made it no longer susceptible to proteinase K-mediated cleavage. In summary, the findings of our study indicate that the S1-S2 linker of Kv1.5 represents a mechanosensor that regulates the activity of this channel. By targeting the S1-S2 linker, mechanical stretch may induce a change in the N-terminal conformation of Kv1.5 that relieves Src-mediated tonic channel inhibition and results in an increase in IKv1.5.
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Affiliation(s)
- Alexandria O Milton
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Tingzhong Wang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Wentao Li
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Jun Guo
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Shetuan Zhang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
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Reduced hybrid/complex N-glycosylation disrupts cardiac electrical signaling and calcium handling in a model of dilated cardiomyopathy. J Mol Cell Cardiol 2019; 132:13-23. [PMID: 31071333 DOI: 10.1016/j.yjmcc.2019.05.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 04/12/2019] [Accepted: 05/01/2019] [Indexed: 12/19/2022]
Abstract
Dilated cardiomyopathy (DCM) is the third most common cause of heart failure, with ~70% of DCM cases considered idiopathic. We showed recently, through genetic ablation of the MGAT1 gene, which encodes an essential glycosyltransferase (GlcNAcT1), that prevention of cardiomyocyte hybrid/complex N-glycosylation was sufficient to cause DCM that led to heart failure and early death. Our findings are consistent with increasing evidence suggesting a link between aberrant glycosylation and heart diseases of acquired and congenital etiologies. However, the mechanisms by which changes in glycosylation contribute to disease onset and progression remain largely unknown. Activity and gating of voltage-gated Na+ and K+ channels (Nav and Kv respectively) play pivotal roles in the initiation, shaping and conduction of cardiomyocyte action potentials (APs) and aberrant channel activity was shown to contribute to cardiac disease. We and others showed that glycosylation can impact Nav and Kv function; therefore, here, we investigated the effects of reduced cardiomyocyte hybrid/complex N-glycosylation on channel activity to investigate whether chronic aberrant channel function can contribute to DCM. Ventricular cardiomyocytes from MGAT1 deficient (MGAT1KO) mice display prolonged APs and pacing-induced aberrant early re-activation that can be attributed to, at least in part, a significant reduction in Kv expression and activity that worsens over time suggesting heart disease-related remodeling. MGAT1KO Nav demonstrate no change in expression or maximal conductance but show depolarizing shifts in voltage-dependent gating. Together, the changes in MGAT1KO Nav and Kv function likely contribute to observed anomalous electrocardiograms and Ca2+ handling. These findings provide insight into mechanisms by which altered glycosylation contributes to DCM through changes in Nav and Kv activity that impact conduction, Ca2+ handling and contraction. The MGAT1KO can also serve as a useful model to study the effects of aberrant electrical signaling on cardiac function and the remodeling events that can occur with heart disease progression.
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Dwenger MM, Ohanyan V, Navedo MF, Nystoriak MA. Coronary microvascular Kv1 channels as regulatory sensors of intracellular pyridine nucleotide redox potential. Microcirculation 2018; 25. [PMID: 29110409 DOI: 10.1111/micc.12426] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 10/30/2017] [Indexed: 12/16/2022]
Abstract
Smooth muscle voltage-gated potassium (Kv) channels are important regulators of microvascular tone and tissue perfusion. Recent studies indicate that Kv1 channels represent a key component of the physiological coupling between coronary blood flow and myocardial oxygen demand. While the mechanisms by which metabolic changes in the heart are transduced to alter coronary Kv1 channel gating and promote vasodilation are unclear, a growing body of evidence underscores a pivotal role of Kv1 channels in sensing the cellular redox status. Here, we discuss current knowledge of mechanisms of Kv channel redox regulation with respect to pyridine nucleotide modulation of Kv1 function via ancillary Kvβ proteins as well as direct modulation of channel activity via reactive oxygen and nitrogen species. We identify areas of additional research to address the integration of regulatory processes under altered physiological and pathophysiological conditions that may reveal insights into novel treatment strategies for conditions in which the matching of coronary blood supply and myocardial oxygen demand is compromised.
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Affiliation(s)
- Marc M Dwenger
- Diabetes and Obesity Center, Institute of Molecular Cardiology, Department of Medicine, University of Louisville, Louisville, KY, USA
| | - Vahagn Ohanyan
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, USA
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, CA, USA
| | - Matthew A Nystoriak
- Diabetes and Obesity Center, Institute of Molecular Cardiology, Department of Medicine, University of Louisville, Louisville, KY, USA
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Lamothe SM, Hogan-Cann AE, Li W, Guo J, Yang T, Tschirhart JN, Zhang S. The N terminus and transmembrane segment S1 of Kv1.5 can coassemble with the rest of the channel independently of the S1-S2 linkage. J Biol Chem 2018; 293:15347-15358. [PMID: 30121572 DOI: 10.1074/jbc.ra118.004065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 08/14/2018] [Indexed: 11/06/2022] Open
Abstract
The voltage-gated potassium channel Kv1.5 belongs to the Shaker superfamily. Kv1.5 is composed of four subunits, each comprising 613 amino acids, which make up the N terminus, six transmembrane segments (S1-S6), and the C terminus. We recently demonstrated that, in HEK cells, extracellularly applied proteinase K (PK) cleaves Kv1.5 channels at a single site in the S1-S2 linker. This cleavage separates Kv1.5 into an N-fragment (N terminus to S1) and a C-fragment (S2 to C terminus). Interestingly, the cleavage does not impair channel function. Here, we investigated the role of the N terminus and S1 in Kv1.5 expression and function by creating plasmids encoding various fragments, including those that mimic PK-cleaved products. Our results disclosed that although expression of the pore-containing fragment (Frag(304-613)) alone could not produce current, coexpression with Frag(1-303) generated a functional channel. Immunofluorescence and biotinylation analyses uncovered that Frag(1-303) was required for Frag(304-613) to traffic to the plasma membrane. Biochemical analysis revealed that the two fragments interacted throughout channel trafficking and maturation. In Frag(1-303)+(304-613)-coassembled channels, which lack a covalent linkage between S1 and S2, amino acid residues 1-209 were important for association with Frag(304-613), and residues 210-303 were necessary for mediating trafficking of coassembled channels to the plasma membrane. We conclude that the N terminus and S1 of Kv1.5 can attract and coassemble with the rest of the channel (i.e. Frag(304-613)) to form a functional channel independently of the S1-S2 linkage.
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Affiliation(s)
- Shawn M Lamothe
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Aja E Hogan-Cann
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Wentao Li
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Jun Guo
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Tonghua Yang
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Jared N Tschirhart
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Shetuan Zhang
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
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Lamothe SM, Hulbert M, Guo J, Li W, Yang T, Zhang S. Glycosylation stabilizes hERG channels on the plasma membrane by decreasing proteolytic susceptibility. FASEB J 2018; 32:1933-1943. [DOI: 10.1096/fj.201700832r] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 11/13/2017] [Indexed: 01/19/2023]
Affiliation(s)
- Shawn M. Lamothe
- Department of Biomedical and Molecular SciencesQueen's UniversityKingstonOntarioCanada
| | - Maggie Hulbert
- Department of Biomedical and Molecular SciencesQueen's UniversityKingstonOntarioCanada
| | - Jun Guo
- Department of Biomedical and Molecular SciencesQueen's UniversityKingstonOntarioCanada
| | - Wentao Li
- Department of Biomedical and Molecular SciencesQueen's UniversityKingstonOntarioCanada
| | - Tonghua Yang
- Department of Biomedical and Molecular SciencesQueen's UniversityKingstonOntarioCanada
| | - Shetuan Zhang
- Department of Biomedical and Molecular SciencesQueen's UniversityKingstonOntarioCanada
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Lamothe SM, Guo J, Li W, Yang T, Zhang S. The Human Ether-a-go-go-related Gene (hERG) Potassium Channel Represents an Unusual Target for Protease-mediated Damage. J Biol Chem 2016; 291:20387-401. [PMID: 27502273 DOI: 10.1074/jbc.m116.743138] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Indexed: 12/22/2022] Open
Abstract
The human ether-a-go-go-related gene (hERG) encodes the pore-forming subunit of the rapidly activating delayed rectifier potassium channel (IKr), which is important for cardiac repolarization. Dysfunction of hERG causes long QT syndrome and sudden death, which occur in patients with cardiac ischemia. Cardiac ischemia is also associated with activation, up-regulation, and secretion of various proteolytic enzymes. Here, using whole-cell patch clamp and Western blotting analysis, we demonstrate that the hERG/IKr channel was selectively cleaved by the serine protease, proteinase K (PK). Using molecular biology techniques including making a chimeric channel between protease-sensitive hERG and insensitive human ether-a-go-go (hEAG), as well as application of the scorpion toxin BeKm-1, we identified that the S5-pore linker of hERG is the target domain for proteinase K cleavage. To investigate the physiological relevance of the unique susceptibility of hERG to proteases, we show that cardiac ischemia in a rabbit model was associated with a reduction in mature ERG expression and an increase in the expression of several proteases, including calpain. Using cell biology approaches, we found that calpain-1 was actively released into the extracellular milieu and cleaved hERG at the S5-pore linker. Using protease cleavage-predicting software and site-directed mutagenesis, we identified that calpain-1 cleaves hERG at position Gly-603 in the S5-pore linker of hERG. Clarification of protease-mediated damage of hERG extends our understanding of hERG regulation. Damage of hERG mediated by proteases such as calpain may contribute to ischemia-associated QT prolongation and sudden cardiac death.
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Affiliation(s)
- Shawn M Lamothe
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Jun Guo
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Wentao Li
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Tonghua Yang
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Shetuan Zhang
- From the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada
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