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Inderwiedenstraße L, Kienitz MC. Angiotensin receptors and α 1B-adrenergic receptors regulate native IK (ACh) and phosphorylation-deficient GIRK4 (S418A) channels through different PKC isoforms. Pflugers Arch 2024; 476:1041-1064. [PMID: 38658400 DOI: 10.1007/s00424-024-02966-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/03/2024] [Accepted: 04/17/2024] [Indexed: 04/26/2024]
Abstract
Signaling of G protein-activated inwardly rectifying K+ (GIRK) channels is an important mechanism of the parasympathetic regulation of the heart rate and cardiac excitability. GIRK channels are inhibited during stimulation of Gq-coupled receptors (GqPCRs) by depletion of phosphatidyl-4,5-bisphosphate (PIP2) and/or channel phosphorylation by protein kinase C (PKC). The GqPCR-dependent modulation of GIRK currents in terms of specific PKC isoform activation was analyzed in voltage-clamp experiments in rat atrial myocytes and in CHO or HEK 293 cells. By using specific PKC inhibitors, we identified the receptor-activated PKC isoforms that contribute to phenylephrine- and angiotensin-induced GIRK channel inhibition. We demonstrate that the cPKC isoform PKCα significantly contributes to GIRK inhibition during stimulation of wildtype α1B-adrenergic receptors (α1B-ARs). Deletion of the α1B-AR serine residues S396 and S400 results in a preferential regulation of GIRK activity by PKCβ. As a novel finding, we report that the AT1-receptor-induced GIRK inhibition depends on the activation of the nPKC isoform PKCε whereas PKCα and PKCβ do not mainly participate in the angiotensin-mediated GIRK reduction. Expression of the dominant negative (DN) PKCε prolonged the onset of GIRK inhibition and significantly reduced AT1-R desensitization, indicating that PKCε regulates both GIRK channel activity and the strength of the receptor signal via a negative feedback mechanism. The serine residue S418 represents an important phosphorylation site for PKCε in the GIRK4 subunit. To analyze the functional impact of this PKC phosphorylation site for receptor-specific GIRK channel modulation, we monitored the activity of a phosphorylation-deficient (GIRK4 (S418A)) GIRK4 channel mutant during stimulation of α1B-ARs or AT1-receptors. Mutation of S418 did not impede α1B-AR-mediated GIRK inhibition, suggesting that S418 within the GIRK4 subunit is not subject to PKCα-induced phosphorylation. Furthermore, activation of angiotensin receptors induced pronounced GIRK4 (S418A) channel inhibition, excluding that this phosphorylation site contributes to the AT1-R-induced GIRK reduction. Instead, phosphorylation of S418 has a facilitative effect on GIRK activity that was abolished in the GIRK4 (S418A) mutant. To summarize, the present study shows that the receptor-dependent regulation of atrial GIRK channels is attributed to the GqPCR-specific activation of different PKC isoforms. Receptor-specific activated PKC isoforms target distinct phosphorylation sites within the GIRK4 subunit, resulting in differential regulation of GIRK channel activity with either facilitative or inhibitory effects on GIRK currents.
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Affiliation(s)
- Leonie Inderwiedenstraße
- Department for Cellular and Translational Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, 44801, Bochum, Germany
| | - Marie-Cécile Kienitz
- Department for Cellular and Translational Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, 44801, Bochum, Germany.
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Renkhold L, Kollmann R, Inderwiedenstraße L, Kienitz MC. PKC-isoform specific regulation of receptor desensitization and KCNQ1/KCNE1 K + channel activity by mutant α 1B-adrenergic receptors. Cell Signal 2021; 91:110228. [PMID: 34958868 DOI: 10.1016/j.cellsig.2021.110228] [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: 10/25/2021] [Revised: 12/20/2021] [Accepted: 12/21/2021] [Indexed: 11/25/2022]
Abstract
Activation of a specific protein kinase C (PKC) isoform during stimulation of Gq protein-coupled receptors (GqPCRs) is determined by homologous receptor desensitization that controls the spatiotemporal formation of downstream Gq signalling molecules. Furthermore, GqPCR-activated PKC isoforms specifically regulate receptor activity via a negative feedback mechanism. In the present study, we investigated the contribution of several phosphorylation sites in the α1B-adrenergic receptor (α1B-AR) for PKC and G protein coupled receptor kinase 2 (GRK2) to homologous receptor desensitization and effector modulation. We analyzed signalling events downstream to human wildtype α1B-ARs and α1B-ARs lacking PKC or GRK2 phosphorylation sites (Δ391-401, α1B-ΔPKC-AR and Δ402-520, α1B-ΔGRK-AR) by means of FRET-based biosensors in HEK293 that served as online-assays of receptor activity. K+ currents through KCNQ1/KCNE1 channels (IKs), which are regulated by both phosphatidylinositol 4,5-bisphosphate (PIP2)-depletion and/or phosphorylation by PKC, were measured as a functional readout of wildtype and mutant α1B-AR receptor activity. As a novel finding, we provide evidence that deletion of PKC and GRK2 phosphorylation sites in α1B-ARs abrogates the contribution of PKCα to homologous receptor desensitization. Instead, the time course of mutant receptor activity was specifically modulated by PKCβ. Mutant α1B-ARs displayed pronounced homologous receptor desensitization that was abolished by PKCβ-specific pharmacological inhibitors. IKs modulation during stimulation of wildtype and mutant α1B-ARs displayed transient inhibition and current facilitation after agonist withdrawal with reduced capability of mutant α1B-ARs to induce IKs inhibition. Pharmacological inhibition of the PKCβ isoform did not augment IKs reduction by mutant α1B-ARs, but shifted IKs modulation towards current facilitation. Coexpression of an inactive (dominant-negative) PKCδ isoform (DN-PKCδ) abolished IKs facilitation in α1B-ΔGRK-AR-expressing cells, but not in α1B-ΔPKC-AR-expressing cells. The data indicate that the differential modulation of IKs activity by α1B-ΔGRK- and α1B-ΔPKC-receptors is attributed to the activation of entirely distinct novel PKC isoforms. To summarize, specific phosphorylation sites within the wildtype and mutant α1B-adrenergic receptors are targeted by different PKC isoforms, resulting in differential regulation of receptor desensitization and effector function.
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Affiliation(s)
- Lina Renkhold
- Klinik für Hautkrankheiten, Universitätsklinikum Münster, Von-Esmarch-Str. 58, D-48149 Münster, Deutschland, Germany
| | - Rike Kollmann
- Department of Cellular Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany
| | - Leonie Inderwiedenstraße
- Department of Cellular Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany
| | - Marie-Cecile Kienitz
- Department of Cellular Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany.
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Gou X, Hu T, Gou Y, Li C, Yi M, Jia M. Specific protein kinase C isoform exerts chronic inhibition on the slowly activating delayed-rectifier potassium current by affecting channel trafficking. Channels (Austin) 2021; 15:262-272. [PMID: 33535882 PMCID: PMC7872027 DOI: 10.1080/19336950.2021.1882112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 01/22/2021] [Accepted: 01/22/2021] [Indexed: 11/04/2022] Open
Abstract
The slowly activating delayed rectifier K+ current (IKs) plays a key role in the repolarization of ventricular action potential in the human heart and is formed by the pore-forming α-subunit encoded by KCNQ1 (Kv7.1) and β-subunit encoded by KCNE1. Evidence suggested that IKs was regulated through protein kinase C (PKC) pathway, but the mechanism is controversial. This study was designed to identify the specific PKC isoform involved in the long-term regulation of IKs current. The IKs current was recorded using whole-cell patch-clamp technique in human embryonic kidney (HEK) 293B cell co-transfected with human KCNQ1/KCNE1 genes. The results revealed that both chronic activation of Ang II and PMA reduced the IKs current in a long-term regulation (about 24 hours). Further evidence showed that PKCε knockdown by siRNA antagonized the AngII-induced chronic inhibition on the IKs current, whereas knockdown of cPKC (PKCα and PKCβ) attenuated the inhibition effect of PMA on the current. Moreover, the forward transport inhibition of the channel with brefeldin A alleviated the Ang II-induced chronic inhibition on IKs current, while the channel endocytosis inhibition with dynasore alleviated both Ang II and PMA-induced chronic inhibition on IKs current. The above results showed that PKCε activation promoted the channel endocytosis and inhibited the channel forward transport to the plasma membrane, while cPKC activation only promoted the channel endocytosis, which both down regulated the channel current.
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Affiliation(s)
- Xiangbo Gou
- Tianjin Key Labortory of Drug Targeting and Bioimaging, Tianjin University of Technology, Tianjin, China
- School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin, China
| | - Tingting Hu
- Department of Orthopaedic Surgery, Tianjin Hospital, Tianjin University, Tianjin, China
- Department of Neurobiology, School of Basic Medical Science, Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing, China
| | - Yu Gou
- Department of Orthopaedic Surgery, Tianjin Hospital, Tianjin University, Tianjin, China
| | - Chaoqi Li
- School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin, China
| | - Ming Yi
- School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin, China
| | - Mengran Jia
- School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin, China
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Zou S, Qiu S, Su S, Zhang J, Sun J, Wang Y, Shi C, Xu Y. Inhibitory G-protein-mediated modulation of slow delayed rectifier potassium channels contributes to increased susceptibility to arrhythmogenesis in aging heart. Heart Rhythm 2021; 18:2197-2209. [PMID: 34536591 DOI: 10.1016/j.hrthm.2021.09.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/20/2021] [Accepted: 09/08/2021] [Indexed: 02/02/2023]
Abstract
BACKGROUND Slow delayed rectifier potassium current (IKs) is an important component of repolarization reserve during sympathetic nerve excitement. However, little is known about age-related functional changes of IKs and its involvement in age-dependent arrhythmogenesis. OBJECTIVE The purpose of this study was to investigate age-related alteration of the IKs response to β-adrenergic receptor (βAR) activation. METHODS Dunkin-Hartley guinea pigs were used. Whole-cell patch-clamp recording was used to record K+ currents. Optical mapping of membrane potential was performed in ex vivo heart. RESULTS There was no difference in IKs density in ventricular cardiomyocytes between young and old guinea pigs. However, in contrast to IKs potentiation in young hearts, isoproterenol (ISO) evoked an acute inhibition on IKs in a concentration-dependent manner in old guinea pig hearts. The β2AR antagonist, but not β1AR antagonist, reversed the inhibitory response. Preincubation of cardiomyocytes with the inhibitory G protein (Gi) inhibitor pertussis toxin (PTX) also reversed the inhibitory response. In HEK293 cells cotransfected with cloned IKs channel and β2AR, ISO enhanced the current but reduced it when cells were cotransfected with Gi2, and PTX restored the ISO-induced excitatory response. Moreover, in aging cardiomyocytes, Gβγ inhibitor gallein, PLC inhibitor U73122, or protein kinase C inhibitor Bis-1 prevented the reduction of IKs by ISO. Furthermore, cardiac-specific Gi2 overexpression in young guinea pigs predisposed the heart to ventricular tachyarrhythmias. PTX pretreatment protected the hearts from ventricular arrhythmias. CONCLUSION βAR activation acutely induces an inhibitory IKs response in aging guinea pig hearts through β2AR-Gi signaling, which contributes to increased susceptibility to arrhythmogenesis in aging hearts.
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Affiliation(s)
- Sihao Zou
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Suhua Qiu
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Shi Su
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Jiali Zhang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Jinglei Sun
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Yuhong Wang
- Institute of Masteria Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Chenxia Shi
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Yanfang Xu
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China.
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Xiao R, Zhao HC, Yan TT, Zhang Q, Huang YS. Angiotensin II and hypoxia induce autophagy in cardiomyocytes via activating specific protein kinase C subtypes. Cardiovasc Diagn Ther 2021; 11:744-759. [PMID: 34295701 DOI: 10.21037/cdt-20-883] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 05/17/2021] [Indexed: 11/06/2022]
Abstract
Background The purpose of this study was to explore the role of protein kinase C (PKC) isozymes and reactive oxygen species (ROS) in hypoxia and angiotensin (Ang) II-induced autophagy. Methods Primary cardiomyocytes were isolated from Sprague-Dawley (SD) neonatal rats and cultured in hypoxia and/or Ang II conditions. Dihydroethidium fluorescence staining was used to detect the content of ROS. Cardiomyocyte autophagy was determined using Monodansylcadaverine fluorescence staining and Western blot. We also inhibited ROS production to explore the relationship between ROS and autophagy. ELISA was used to detect the contents of PKC δ and PKC ε. After inhibition of PKC δ activation and PKC ε expression by lentiviral siRNA, ROS content and autophagy of cultured cardiomyocytes were detected. Results Hypoxia and Ang II stimulation increased autophagy in cardiomyocytes, accompanied by increased intracellular ROS production. Inhibiting ROS following hypoxia or Ang II stimulation significantly suppressed autophagy in comparison with hypoxia or Ang II stimulation group. Inhibiting PKC δ significantly reduced ROS production and autophagy activity following hypoxia or accompanied with Ang II stimulation except Ang II stimulation alone. Knockdown of PKC ε notably decreased ROS production and autophagy in response to Ang II alone and in combination with hypoxia rather than hypoxia alone. Conclusions Both hypoxia and Ang II stimulation can induce autophagy in cardiomyocytes through increasing intracellular ROS. However, hypoxia and Ang II stimulation induced myocardial autophagy via PKC δ and PKC ε, respectively.
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Affiliation(s)
- Rong Xiao
- Burn Center of PLA, No. 990 Hospital of PLA, Zhumadian, China
| | - Hai-Chun Zhao
- Burn Center of PLA, No. 990 Hospital of PLA, Zhumadian, China
| | - Tian-Tian Yan
- Burn Center of PLA, No. 990 Hospital of PLA, Zhumadian, China
| | - Qiong Zhang
- Institute of Burn Research, State Key Laboratory of Trauma, Burns and Combined Injury, Southwest Hospital, The Third Military Medical University, Chongqing, China
| | - Yue-Sheng Huang
- Department of Wound Repair, Institute of Wound Repair, Shenzhen People's Hospital, the First Affiliated Hospital of Southern University of Science and Technology, and the Second Clinical Medical College of Jinan University, Shenzhen, China
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Xu T, Fan X, Zhao M, Wu M, Li H, Ji B, Zhu X, Li L, Ding H, Sun M, Xu Z, Gao Q. DNA Methylation-Reprogrammed Ang II (Angiotensin II) Type 1 Receptor-Early Growth Response Gene 1-Protein Kinase C ε Axis Underlies Vascular Hypercontractility in Antenatal Hypoxic Offspring. Hypertension 2020; 77:491-506. [PMID: 33342239 DOI: 10.1161/hypertensionaha.120.16247] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
As the most common clinical stress during mid and late pregnancy, antenatal hypoxia has profound adverse effects on individual's vascular health later in life, but the underlying mechanisms are still not understood. The purpose of this study was to reveal the mechanisms of the acquired vascular dysfunction in offspring imposed by antenatal hypoxia. Pregnant rats were housed in a normoxic or hypoxic (10.5% oxygen) chamber from gestation day 10 to 21. Male offspring were euthanized at gestational day 21 (fetus) or postnatal 16 weeks old (adult offspring). Mesenteric arteries were collected for examining Ang II (angiotensin II)-mediated vascular contractility, gene expression, and promoter methylation. Antenatal hypoxia increased vascular sensitivity to Ang II, which was resulted by an upregulated AT1R (angiotensin II type 1 receptor). The increased AT1R was correlated with a hypomethylation-mediated activated transcription of Agtr1a (alpha subtype of AT1R). In addition, we presented evidences that there was an AT1R-Egr1 (early growth response gene 1)-PKCε (ε isoform of protein kinase C) axis in vasculature; AT1R could modulate PKCε expression via upregulating Egr1; Egr1 mediated transcription activation of PKCε via Egr1 binding sites in PKCε gene promoter. Overall, antenatal hypoxia activated AT1R-Egr1-PKCε axis in vasculature, eventually predisposed offspring to vascular hypercontractility. This is the first description that antenatal hypoxia resulted in vascular adverse outcomes in postnatal offspring, was strongly associated with reprogrammed gene expression via a DNA methylation-mediated epigenetic mechanism, advancing understanding toward the influence of adverse antenatal factors in early life on long-term vascular health.
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Affiliation(s)
- Ting Xu
- From the Institute for Fetology (T.X., M.Z., H.L., B.J., X.Z., L.L., M.S., Z.X., Q.G.), First Hospital of Soochow University, Suzhou, China
| | - Xiaorong Fan
- Institute of Reproductive Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China (X.F.)
| | - Meng Zhao
- From the Institute for Fetology (T.X., M.Z., H.L., B.J., X.Z., L.L., M.S., Z.X., Q.G.), First Hospital of Soochow University, Suzhou, China
| | - Meng Wu
- Institutes of Biological and Medical Sciences, Soochow University Medical School, Suzhou, China (M.W.)
| | - Huan Li
- From the Institute for Fetology (T.X., M.Z., H.L., B.J., X.Z., L.L., M.S., Z.X., Q.G.), First Hospital of Soochow University, Suzhou, China
| | - Bingyu Ji
- From the Institute for Fetology (T.X., M.Z., H.L., B.J., X.Z., L.L., M.S., Z.X., Q.G.), First Hospital of Soochow University, Suzhou, China
| | - Xiaolin Zhu
- From the Institute for Fetology (T.X., M.Z., H.L., B.J., X.Z., L.L., M.S., Z.X., Q.G.), First Hospital of Soochow University, Suzhou, China
| | - Lingjun Li
- From the Institute for Fetology (T.X., M.Z., H.L., B.J., X.Z., L.L., M.S., Z.X., Q.G.), First Hospital of Soochow University, Suzhou, China
| | - Hongmei Ding
- Department of Obstetrics and Gynecology (H.D.), First Hospital of Soochow University, Suzhou, China
| | - Miao Sun
- From the Institute for Fetology (T.X., M.Z., H.L., B.J., X.Z., L.L., M.S., Z.X., Q.G.), First Hospital of Soochow University, Suzhou, China
| | - Zhice Xu
- From the Institute for Fetology (T.X., M.Z., H.L., B.J., X.Z., L.L., M.S., Z.X., Q.G.), First Hospital of Soochow University, Suzhou, China
| | - Qinqin Gao
- From the Institute for Fetology (T.X., M.Z., H.L., B.J., X.Z., L.L., M.S., Z.X., Q.G.), First Hospital of Soochow University, Suzhou, China
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Shugg T, Hudmon A, Overholser BR. Neurohormonal Regulation of I Ks in Heart Failure: Implications for Ventricular Arrhythmogenesis and Sudden Cardiac Death. J Am Heart Assoc 2020; 9:e016900. [PMID: 32865116 PMCID: PMC7726975 DOI: 10.1161/jaha.120.016900] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Heart failure (HF) results in sustained alterations in neurohormonal signaling, including enhanced signaling through the sympathetic nervous system and renin-angiotensin-aldosterone system pathways. While enhanced sympathetic nervous system and renin-angiotensin-aldosterone system activity initially help compensate for the failing myocardium, sustained signaling through these pathways ultimately contributes to HF pathophysiology. HF remains a leading cause of mortality, with arrhythmogenic sudden cardiac death comprising a common mechanism of HF-related death. The propensity for arrhythmia development in HF occurs secondary to cardiac electrical remodeling that involves pathological regulation of ventricular ion channels, including the slow component of the delayed rectifier potassium current, that contribute to action potential duration prolongation. To elucidate a mechanistic explanation for how HF-mediated electrical remodeling predisposes to arrhythmia development, a multitude of investigations have investigated the specific regulatory effects of HF-associated stimuli, including enhanced sympathetic nervous system and renin-angiotensin-aldosterone system signaling, on the slow component of the delayed rectifier potassium current. The objective of this review is to summarize the current knowledge related to the regulation of the slow component of the delayed rectifier potassium current in response to HF-associated stimuli, including the intracellular pathways involved and the specific regulatory mechanisms.
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Affiliation(s)
- Tyler Shugg
- Division of Clinical PharmacologyIndiana University School of MedicineIndianapolisIN
| | - Andy Hudmon
- Department of Medicinal Chemistry and Molecular PharmacologyPurdue University College of PharmacyWest LafayetteIN
| | - Brian R. Overholser
- Division of Clinical PharmacologyIndiana University School of MedicineIndianapolisIN
- Department of Pharmacy PracticePurdue University College of PharmacyIndianapolisIN
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Fan C, Liang W, Wei M, Gou X, Han S, Bai J. Effects of D-Chiro-Inositol on Glucose Metabolism in db/db Mice and the Associated Underlying Mechanisms. Front Pharmacol 2020; 11:354. [PMID: 32273844 PMCID: PMC7113635 DOI: 10.3389/fphar.2020.00354] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Accepted: 03/10/2020] [Indexed: 01/16/2023] Open
Abstract
In this study, we observed the effect of D-chiro-inositol (DCI) on glucose consumption in type 2 diabetic db/db mice, and investigated the relevant mechanism. We discovered that the stability of 24-h blood glucose under the nonfasting condition and decreased glucose tolerance were both alleviated after treatment with DCI. Moreover, the content of glycosylated protein and advanced glycation end products in the serum was reduced, the damage in the liver tissue was alleviated, and the synthesis of liver glycogen was significantly promoted. In addition, DCI increased the expression of insulin receptor substrate 2 (IRS2), phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), glucose transporters 4 (GLUT4), and phospho-AKT (S473) protein. In contrast, DCI decreased the expression level of glycogen synthase kinase 3β (GSK3β) protein in liver tissue to various degrees, as shown by immunohistochemistry and western blotting. Furthermore, DCI increased the mRNA expression of IRS2, PI3K, AKT, and GLUT4, and reduced that of GSK3β in liver tissue, as demonstrated by polymerase chain reaction. Finally, DCI promoted glucose consumption in high glucose-stimulating HepG2 cells and increased the expression of IRS2 protein in HepG2 cells, as revealed by fluorescence staining and flow cytometry. Our results indicate that DCI can significantly improve glucose metabolism in diabetic mice and HepG2 cells. This effect may be associated with the upregulation of IRS2, PI3K, AKT, and GLUT4 and downregulation of GSK3β.
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Affiliation(s)
- Chunxue Fan
- School of Pharmacy, North China University of Science and Technology, Tangshan, China
| | - Weishi Liang
- Clinical Medical College, North China University of Science and Technology, Tangshan, China
| | - Min Wei
- Clinical Medical College, North China University of Science and Technology, Tangshan, China
| | - Xiangbo Gou
- School of Basic Medical Sciences, North China University of Science and Technology, Tangshan, China
| | - Shuying Han
- School of Basic Medical Sciences, North China University of Science and Technology, Tangshan, China
| | - Jing Bai
- School of Basic Medical Sciences, North China University of Science and Technology, Tangshan, China
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Platzer D, Zorn-Pauly K. Accuracy considerations for capacitance estimation by voltage steps in cardiomyocytes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 157:3-10. [PMID: 32217074 DOI: 10.1016/j.pbiomolbio.2020.03.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 03/03/2020] [Accepted: 03/09/2020] [Indexed: 10/24/2022]
Abstract
Electrophysiologists routinely use simple voltage steps to evaluate cell membrane capacitance derived from corresponding current responses. Frequently, the resting membrane voltage Vrest is employed as holding potential for the subsequent command voltage step and more or less accurate methods are utilised to analyse the transient current. Another choice as holding potential is the peak of the "quasi steady-state" current to voltage relationship, Vpeak. The aim of this study is the systematic evaluation of capacitance estimation accuracy from voltage step experiments depending on the choice of holding potential and analysis method. In this paper, a simulation approach is employed to analyse the current response of a model patch-clamp circuit. Four commonly accepted methods are implemented, utilizing different aspects of the transient current (charge, membrane time constant, and influence of the series resistance) in various combinations and with various degrees of refinement. This simulation study indicates an acceptable accuracy of the elaborated methods for capacitance estimation at holding potentials Vrest and Vpeak over a broad range of capacitance as well as series resistance values. Simple integration of the current transient provides sufficient accuracy at holding potentials, which effectively minimizes changes in resistive membrane current flow during command voltage steps (particularly around Vpeak). However, biphasic command protocols performed at Vpeak activate voltage dependent sodium channels, thereby possibly leading to the threshold voltage for an action potential. Compared to Vrest, all methods utilizing monophasic step protocols, gain additional accuracy, when applied at Vpeak as holding potential.
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Affiliation(s)
- Dieter Platzer
- Chair of Biophysics, Gottfried Schatz Research Center, Medical University Graz, Neue Stiftingtalstraße 6/IV, 8010, Graz, Austria
| | - Klaus Zorn-Pauly
- Chair of Biophysics, Gottfried Schatz Research Center, Medical University Graz, Neue Stiftingtalstraße 6/IV, 8010, Graz, Austria.
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Ardestani G, West MC, Maresca TJ, Fissore RA, Stratton MM. FRET-based sensor for CaMKII activity (FRESCA): A useful tool for assessing CaMKII activity in response to Ca 2+ oscillations in live cells. J Biol Chem 2019; 294:11876-11891. [PMID: 31201271 DOI: 10.1074/jbc.ra119.009235] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 06/11/2019] [Indexed: 01/22/2023] Open
Abstract
Ca2+ oscillations and consequent Ca2+/calmodulin-dependent protein kinase II (CaMKII) activation are required for embryogenesis, as well as neuronal, immunological, and cardiac signaling. Fertilization directly results in Ca2+ oscillations, but the resultant pattern of CaMKII activity remains largely unclear. To address this gap, we first employed the one existing biosensor for CaMKII activation. This sensor, Camui, comprises CaMKIIα and therefore solely reports on the activation of this CaMKII variant. Additionally, to detect the activity of all endogenous CaMKII variants simultaneously, we constructed a substrate-based sensor for CaMKII activity, FRESCA (FRET-based sensor for CaMKII activity). To examine the differential responses of the Camui and FRESCA sensors, we used several approaches to stimulate Ca2+ release in mouse eggs, including addition of phospholipase Cζ cRNA, which mimics natural fertilization. We found that the Camui response is delayed or terminates earlier than the FRESCA response. FRESCA enables assessment of endogenous CaMKII activity in real-time by both fertilization and artificial reagents, such as Sr2+, which also leads to CaMKII activation. FRESCA's broad utility will be important for optimizing artificial CaMKII activation for clinical use to manage infertility. Moreover, FRESCA provides a new view on CaMKII activity, and its application in additional biological systems may reveal new signaling paradigms in eggs, as well as in neurons, cardiomyocytes, immune cells, and other CaMKII-expressing cells.
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Affiliation(s)
- Goli Ardestani
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, Massachusetts 01003.,Veterinary and Animal Sciences Graduate Program, University of Massachusetts, Amherst, Massachusetts 01003
| | - Megan C West
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Thomas J Maresca
- Department of Biology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Rafael A Fissore
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, Massachusetts 01003
| | - Margaret M Stratton
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003
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