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Whelan SCM, Mutchler SM, Han A, Priestley C, Satlin LM, Kleyman TR, Shi S. Kcnma1 alternative splicing in mouse kidney: regulation during development and by dietary K + intake. Am J Physiol Renal Physiol 2024; 327:F49-F60. [PMID: 38779757 DOI: 10.1152/ajprenal.00100.2024] [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: 03/29/2024] [Revised: 04/30/2024] [Accepted: 05/08/2024] [Indexed: 05/25/2024] Open
Abstract
The pore-forming α-subunit of the large-conductance K+ (BK) channel is encoded by a single gene, KCNMA1. BK channel-mediated K+ secretion in the kidney is crucial for overall renal K+ homeostasis in both physiological and pathological conditions. BK channels achieve phenotypic diversity by various mechanisms, including substantial exon rearrangements at seven major alternative splicing sites. However, KCNMA1 alternative splicing in the kidney has not been characterized. The present study aims to identify the major splice variants of mouse Kcnma1 in whole kidney and distal nephron segments. We designed primers that specifically cross exons within each alternative splice site of mouse Kcnma1 and performed real-time quantitative RT-PCR (RT-qPCR) to quantify relative abundance of each splice variant. Our data suggest that Kcnma1 splice variants within mouse kidney are less diverse than in the brain. During postnatal kidney development, most Kcnma1 splice variants at site 5 and the COOH terminus increase in abundance over time. Within the kidney, the regulation of Kcnma1 alternative exon splicing within these two sites by dietary K+ loading is both site and sex specific. In microdissected distal tubules, the Kcnma1 alternative splicing profile, as well as its regulation by dietary K+, are distinctly different than in the whole kidney, suggesting segment and/or cell type specificity in Kcnma1 splicing events. Overall, our data provide evidence that Kcnma1 alternative splicing is regulated during postnatal development and may serve as an important adaptive mechanism to dietary K+ loading in mouse kidney.NEW & NOTEWORTHY We identified the major Kcnma1 splice variants that are specifically expressed in the whole mouse kidney or aldosterone-sensitive distal nephron segments. Our data suggest that Kcnma1 alternative splicing is developmentally regulated and subject to changes in dietary K+.
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Affiliation(s)
| | - Stephanie M Mutchler
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Agnes Han
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Catherine Priestley
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Lisa M Satlin
- Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York, New York, United States
| | - Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Shujie Shi
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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2
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Jansen SC, van Lemmen M, Olofsen E, Moss L, Pergolizzi JV, Miller T, Colucci RD, van Velzen M, Kremer P, Dahan A, van der Schrier R, Niesters M. Reversal of Propofol-induced Depression of the Hypoxic Ventilatory Response by BK-channel Blocker ENA-001: A Randomized Controlled Trial. Anesthesiology 2024; 140:1076-1087. [PMID: 38241294 PMCID: PMC11097949 DOI: 10.1097/aln.0000000000004915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 01/11/2024] [Indexed: 01/21/2024]
Abstract
BACKGROUND The use of anesthetics may result in depression of the hypoxic ventilatory response. Since there are no receptor-specific antagonists for most anesthetics, there is the need for agnostic respiratory stimulants that increase respiratory drive irrespective of its cause. The authors tested whether ENA-001, an agnostic respiratory stimulant that blocks carotid body BK-channels, could restore the hypoxic ventilatory response during propofol infusion. They hypothesize that ENA-001 is able to fully restore the hypoxic ventilatory response. METHODS In this randomized, double-blind crossover trial, 14 male and female healthy volunteers were randomized to receive placebo and low- and high-dose ENA-001 on three separate occasions. On each occasion, isohypercapnic hypoxic ventilatory responses were measured during a fixed sequence of placebo, followed by low- and high-dose propofol infusion. The authors conducted a population pharmacokinetic/pharmacodynamic analysis that included oxygen and carbon dioxide kinetics. RESULTS Twelve subjects completed the three sessions; no serious adverse events occurred. The propofol concentrations were 0.6 and 2.0 µg/ml at low and high dose, respectively. The ENA-001 concentrations were 0.6 and 1.0 µg/ml at low and high dose, respectively. The propofol concentration that reduced the hypoxic ventilatory response by 50% was 1.47 ± 0.20 µg/ml. The steady state ENA-001 concentration to increase the depressed ventilatory response by 50% was 0.51 ± 0.04 µg/ml. A concentration of 1 µg/ml ENA-001 was required for full reversal of the propofol effect at the propofol concentration that reduced the hypoxic ventilatory response by 50%. CONCLUSIONS In this pilot study, the authors demonstrated that ENA-001 restored the hypoxic ventilatory response impaired by propofol. This finding is not only of clinical importance but also provides mechanistic insights into the peripheral stimulation of breathing with ENA-001 overcoming central depression by propofol. EDITOR’S PERSPECTIVE
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Affiliation(s)
- Simone C. Jansen
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Maarten van Lemmen
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Erik Olofsen
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Laurence Moss
- Centre for Human Drug Research, Leiden, The Netherlands
| | - Joseph V. Pergolizzi
- Enalare Therapeutics Inc., Princeton, New Jersey; NEMA Research Inc., Naples, Florida
| | - Thomas Miller
- Enalare Therapeutics Inc., Princeton, New Jersey; Department of Pediatrics, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Robert D. Colucci
- NEMA Research Inc., Naples, Florida; Colucci & Associates, LLC, Newtown, Connecticut
| | - Monique van Velzen
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Philip Kremer
- Centre for Human Drug Research, Leiden, The Netherlands
| | - Albert Dahan
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands; PainLess Foundation, Leiden, The Netherlands
| | | | - Marieke Niesters
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands; PainLess Foundation, Leiden, The Netherlands
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Timofeyenko K, Kanavalau D, Alexiou P, Kalyna M, Růžička K. Catsnap: a user-friendly algorithm for determining the conservation of protein variants reveals extensive parallelisms in the evolution of alternative splicing. THE NEW PHYTOLOGIST 2023; 238:1722-1732. [PMID: 36751910 PMCID: PMC10952736 DOI: 10.1111/nph.18799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 01/27/2023] [Indexed: 06/18/2023]
Abstract
Understanding the evolutionary conservation of complex eukaryotic transcriptomes significantly illuminates the physiological relevance of alternative splicing (AS). Examining the evolutionary depth of a given AS event with ordinary homology searches is generally challenging and time-consuming. Here, we present Catsnap, an algorithmic pipeline for assessing the conservation of putative protein isoforms generated by AS. It employs a machine learning approach following a database search with the provided pair of protein sequences. We used the Catsnap algorithm for analyzing the conservation of emerging experimentally characterized alternative proteins from plants and animals. Indeed, most of them are conserved among other species. Catsnap can detect the conserved functional protein isoforms regardless of the AS type by which they are generated. Notably, we found that while the primary amino acid sequence is maintained, the type of AS determining the inclusion or exclusion of protein regions varies throughout plant phylogenetic lineages in these proteins. We also document that this phenomenon is less seen among animals. In sum, our algorithm highlights the presence of unexpectedly frequent hotspots where protein isoforms recurrently arise to carry physiologically relevant functions. The user web interface is available at https://catsnap.cesnet.cz/.
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Affiliation(s)
- Ksenia Timofeyenko
- Laboratory of Hormonal Regulations in Plants, Institute of Experimental BotanyCzech Academy of Sciences165 02Prague 6Czech Republic
- Functional Genomics and Proteomics of Plants and National Centre for Biomolecular ResearchMasaryk University625 00BrnoCzech Republic
| | | | - Panagiotis Alexiou
- Central European Institute of TechnologyMasaryk University625 00BrnoCzech Republic
| | - Maria Kalyna
- Department of Applied Genetics and Cell Biology, Institute of Molecular Plant BiologyUniversity of Natural Resources and Life Sciences (BOKU)1190ViennaAustria
| | - Kamil Růžička
- Laboratory of Hormonal Regulations in Plants, Institute of Experimental BotanyCzech Academy of Sciences165 02Prague 6Czech Republic
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The Use of Caffeine Citrate for Respiratory Stimulation in Acquired Central Hypoventilation Syndrome: A Case Series. J Crit Care Med (Targu Mures) 2023; 9:49-54. [PMID: 36890973 PMCID: PMC9987273 DOI: 10.2478/jccm-2023-0003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 12/27/2022] [Indexed: 02/11/2023] Open
Abstract
Introductions Caffeine is commonly used as a respiratory stimulant for the treatment of apnea of prematurity in neonates. However, there are no reports to date of caffeine used to improve respiratory drive in adult patients with acquired central hypoventilation syndrome (ACHS). Presentation of case series We report two cases of ACHS who were successfully liberated from mechanical ventilation after caffeine use, without side effects. The first case was a 41-year-old ethnic Chinese male, diagnosed with high-grade astrocytoma in the right hemi-pons, intubated and admitted to the intensive care unit (ICU) in view of central hypercapnia with intermittent apneic episodes. Oral caffeine citrate (1600mg loading followed by 800mg once daily) was initiated. His ventilator support was weaned successfully after 12 days. The second case was a 65-year-old ethnic Indian female, diagnosed with posterior circulation stroke. She underwent posterior fossa decompressive craniectomy and insertion of an extra-ventricular drain. Post-operatively, she was admitted to the ICU and absence of spontaneous breath was observed for 24 hours. Oral caffeine citrate (300mg twice daily) was initiated and she regained spontaneous breath after 2 days of treatment. She was extubated and discharged from the ICU. Conclusion Oral caffeine was an effective respiratory stimulant in the above patients with ACHS. Larger randomized controlled studies are needed to determine its efficacy in the treatment of ACHS in adult patients.
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Ochoa SV, Otero L, Aristizabal-Pachon AF, Hinostroza F, Carvacho I, Torres YP. Hypoxic Regulation of the Large-Conductance, Calcium and Voltage-Activated Potassium Channel, BK. Front Physiol 2022; 12:780206. [PMID: 35002762 PMCID: PMC8727448 DOI: 10.3389/fphys.2021.780206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/15/2021] [Indexed: 11/15/2022] Open
Abstract
Hypoxia is a condition characterized by a reduction of cellular oxygen levels derived from alterations in oxygen balance. Hypoxic events trigger changes in cell-signaling cascades, oxidative stress, activation of pro-inflammatory molecules, and growth factors, influencing the activity of various ion channel families and leading to diverse cardiovascular diseases such as myocardial infarction, ischemic stroke, and hypertension. The large-conductance, calcium and voltage-activated potassium channel (BK) has a central role in the mechanism of oxygen (O2) sensing and its activity has been related to the hypoxic response. BK channels are ubiquitously expressed, and they are composed by the pore-forming α subunit and the regulatory subunits β (β1–β4), γ (γ1–γ4), and LINGO1. The modification of biophysical properties of BK channels by β subunits underly a myriad of physiological function of these proteins. Hypoxia induces tissue-specific modifications of BK channel α and β subunits expression. Moreover, hypoxia modifies channel activation kinetics and voltage and/or calcium dependence. The reported effects on the BK channel properties are associated with events such as the increase of reactive oxygen species (ROS) production, increases of intracellular Calcium ([Ca2+]i), the regulation by Hypoxia-inducible factor 1α (HIF-1α), and the interaction with hemeproteins. Bronchial asthma, chronic obstructive pulmonary diseases (COPD), and obstructive sleep apnea (OSA), among others, can provoke hypoxia. Untreated OSA patients showed a decrease in BK-β1 subunit mRNA levels and high arterial tension. Treatment with continuous positive airway pressure (CPAP) upregulated β1 subunit mRNA level, decreased arterial pressures, and improved endothelial function coupled with a reduction in morbidity and mortality associated with OSA. These reports suggest that the BK channel has a role in the response involved in hypoxia-associated hypertension derived from OSA. Thus, this review aims to describe the mechanisms involved in the BK channel activation after a hypoxic stimulus and their relationship with disorders like OSA. A deep understanding of the molecular mechanism involved in hypoxic response may help in the therapeutic approaches to treat the pathological processes associated with diseases involving cellular hypoxia.
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Affiliation(s)
- Sara V Ochoa
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.,Semillero de Investigación, Biofísica y Fisiología de Canales Iónicos, Pontificia Universidad Javeriana, Bogotá, Colombia
| | - Liliana Otero
- Center of Dental Research Dentistry Faculty, Pontificia Universidad Javeriana, Bogotá, Colombia
| | | | - Fernando Hinostroza
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del Maule, Talca, Chile.,Centro de Investigación de Estudios Avanzados del Maule, CIEAM, Vicerrectoría de Investigación y Postgrado, Universidad Católica del Maule, Talca, Chile.,Facultad de Ciencias de la Salud, Centro de Investigación en Neuropsicología y Neurociencias Cognitivas, Universidad Católica del Maule, Talca, Chile
| | - Ingrid Carvacho
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del Maule, Talca, Chile
| | - Yolima P Torres
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.,Semillero de Investigación, Biofísica y Fisiología de Canales Iónicos, Pontificia Universidad Javeriana, Bogotá, Colombia
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6
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Sancho M, Kyle BD. The Large-Conductance, Calcium-Activated Potassium Channel: A Big Key Regulator of Cell Physiology. Front Physiol 2021; 12:750615. [PMID: 34744788 PMCID: PMC8567177 DOI: 10.3389/fphys.2021.750615] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/29/2021] [Indexed: 12/01/2022] Open
Abstract
Large-conductance Ca2+-activated K+ channels facilitate the efflux of K+ ions from a variety of cells and tissues following channel activation. It is now recognized that BK channels undergo a wide range of pre- and post-translational modifications that can dramatically alter their properties and function. This has downstream consequences in affecting cell and tissue excitability, and therefore, function. While finding the “silver bullet” in terms of clinical therapy has remained elusive, ongoing research is providing an impressive range of viable candidate proteins and mechanisms that associate with and modulate BK channel activity, respectively. Here, we provide the hallmarks of BK channel structure and function generally, and discuss important milestones in the efforts to further elucidate the diverse properties of BK channels in its many forms.
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Affiliation(s)
- Maria Sancho
- Department of Pharmacology, University of Vermont, Burlington, VT, United States
| | - Barry D Kyle
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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7
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Peppin JF, Pergolizzi Jr JV, Fudin J, Meyer TA, Raffa RB. History of Respiratory Stimulants. J Pain Res 2021; 14:1043-1049. [PMID: 33889020 PMCID: PMC8057823 DOI: 10.2147/jpr.s298607] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/02/2021] [Indexed: 11/24/2022] Open
Abstract
The interest in substances that stimulate respiration has waxed and waned throughout the years, intensifying following the introduction of a new class of drugs that causes respiratory depression, and diminishing when antidotes or better drug alternatives are found. Examples include the opioids--deaths increasing during overprescribing, diminishing with wider availability of the opioid receptor antagonist naloxone, increasing again during COVID-19; the barbiturates--until largely supplanted by the benzodiazepines; propofol; and other central nervous system depressants. Unfortunately, two new troubling phenomena force a reconsideration of the status-quo: (1) overdoses due to highly potent opioids such as fentanyl, and even more-potent licit and illicit fentanyl analogs, and (2) overdose due to polysubstance use (the combination of an opioid plus one or more non-opioid drug, such as a benzodiazepine, sedating antidepressant, skeletal muscle relaxant, or various other agents). Since these now represent the majority of cases, new solutions are again needed. An interest in respiratory stimulants has been revived. This interest can be informed by a short review of the history of this interesting class of medications. We present a short history of the trajectory of advances toward more selective and safer respiratory stimulants.
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Affiliation(s)
- John F Peppin
- Marian University College of Osteopathic Medicine, Indianapolis, IN, USA
- Pikeville University College of Osteopathic Medicine, Pikeville, KY, USA
| | - Joseph V Pergolizzi Jr
- Enalare Therapeutics Inc., Princeton, NJ, USA
- NEMA Research Inc., Naples, FL, USA
- Neumentum Inc., Summit, NJ, USA
| | - Jeffrey Fudin
- Western New England College of Pharmacy, Springfield, MA, USA
- Albany College of Pharmacy & Health Sciences Union University, Albany, NY, USA
- Remitigate Therapeutics, Delmar, NY, USA
| | | | - Robert B Raffa
- Enalare Therapeutics Inc., Princeton, NJ, USA
- Neumentum Inc., Summit, NJ, USA
- University of Arizona College of Pharmacy, Tucson, AZ, USA
- Temple University School of Pharmacy, Philadelphia, PA, USA
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8
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Peppin JF, Pergolizzi JV, Gan TJ, Raffa RB. The problem of postoperative respiratory depression. J Clin Pharm Ther 2021; 46:1220-1225. [PMID: 33655504 DOI: 10.1111/jcpt.13382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 01/24/2021] [Accepted: 02/06/2021] [Indexed: 11/30/2022]
Abstract
WHAT IS KNOWN AND OBJECTIVE Postsurgical recovery is influenced by multiple pre-, intra- and perioperative pharmacotherapeutic interventions, including the administration of medications that can induce respiratory depression postoperatively. We present a succinct overview of the topic, including the nature and magnitude of the problem, contributing factors, current limited options, and potential novel therapeutic approach. COMMENT Pre-, intra- and perioperative medications are commonly administered for anxiety, anaesthesia, muscle relaxation and pain relief among other reasons. Several of the medications alone or in joint-action can be additive or synergistic producing respiratory depression. Given the large number of surgical procedures that are performed each year, even a small percentage of postoperative respiratory complications translates into a large number of affected patients. WHAT IS NEW AND CONCLUSION Due to the large number of surgeries performed each year, and the variety of medications used before, during, and after surgery, the occurrence of postoperative respiratory depression is surprisingly common. It is a significant medical problem and burden on hospital resources. There is a need for new strategies to prevent and treat the acute and collateral problems associated with postoperative respiratory depression.
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Affiliation(s)
- John F Peppin
- Marian University College of Osteopathic Medicine (Clinical Adjunct Professor), Indianapolis, IN, USA.,Pikeville University College of Osteopathic Medicine (Clinical Professor), Pikeville, KY, USA
| | - Joseph V Pergolizzi
- Enalare Therapeutics Inc, Princeton, NJ, USA.,Neumentum Inc, Summit, NJ, USA.,NEMA Research Inc, Naples, FL, USA
| | - Tong J Gan
- Department of Anesthesiology, Stony Brook Renaissance School of Medicine, Stony Brook, NY, USA
| | - Robert B Raffa
- Enalare Therapeutics Inc, Princeton, NJ, USA.,Neumentum Inc, Summit, NJ, USA.,University of Arizona College of Pharmacy (Adjunct Professor), Tucson, AZ, USA.,Temple University School of Pharmacy (Professor Emeritus), Philadelphia, PA, USA
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9
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Shah N, Zhou L. Regulation of Ion Channel Function by Gas Molecules. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1349:139-164. [DOI: 10.1007/978-981-16-4254-8_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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10
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Farina AR, Cappabianca L, Sebastiano M, Zelli V, Guadagni S, Mackay AR. Hypoxia-induced alternative splicing: the 11th Hallmark of Cancer. J Exp Clin Cancer Res 2020; 39:110. [PMID: 32536347 PMCID: PMC7294618 DOI: 10.1186/s13046-020-01616-9] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 06/03/2020] [Indexed: 12/16/2022] Open
Abstract
Hypoxia-induced alternative splicing is a potent driving force in tumour pathogenesis and progression. In this review, we update currents concepts of hypoxia-induced alternative splicing and how it influences tumour biology. Following brief descriptions of tumour-associated hypoxia and the pre-mRNA splicing process, we review the many ways hypoxia regulates alternative splicing and how hypoxia-induced alternative splicing impacts each individual hallmark of cancer. Hypoxia-induced alternative splicing integrates chemical and cellular tumour microenvironments, underpins continuous adaptation of the tumour cellular microenvironment responsible for metastatic progression and plays clear roles in oncogene activation and autonomous tumour growth, tumor suppressor inactivation, tumour cell immortalization, angiogenesis, tumour cell evasion of programmed cell death and the anti-tumour immune response, a tumour-promoting inflammatory response, adaptive metabolic re-programming, epithelial to mesenchymal transition, invasion and genetic instability, all of which combine to promote metastatic disease. The impressive number of hypoxia-induced alternative spliced protein isoforms that characterize tumour progression, classifies hypoxia-induced alternative splicing as the 11th hallmark of cancer, and offers a fertile source of potential diagnostic/prognostic markers and therapeutic targets.
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Affiliation(s)
- Antonietta Rosella Farina
- Department of Applied Clinical and Biotechnological Sciences, University of L’Aquila, 67100 L’Aquila, Italy
| | - Lucia Cappabianca
- Department of Applied Clinical and Biotechnological Sciences, University of L’Aquila, 67100 L’Aquila, Italy
| | - Michela Sebastiano
- Department of Applied Clinical and Biotechnological Sciences, University of L’Aquila, 67100 L’Aquila, Italy
| | - Veronica Zelli
- Department of Applied Clinical and Biotechnological Sciences, University of L’Aquila, 67100 L’Aquila, Italy
| | - Stefano Guadagni
- Department of Applied Clinical and Biotechnological Sciences, University of L’Aquila, 67100 L’Aquila, Italy
| | - Andrew Reay Mackay
- Department of Applied Clinical and Biotechnological Sciences, University of L’Aquila, 67100 L’Aquila, Italy
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Dopico AM, Bukiya AN, Jaggar JH. Calcium- and voltage-gated BK channels in vascular smooth muscle. Pflugers Arch 2018; 470:1271-1289. [PMID: 29748711 DOI: 10.1007/s00424-018-2151-y] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 04/27/2018] [Indexed: 02/04/2023]
Abstract
Ion channels in vascular smooth muscle regulate myogenic tone and vessel contractility. In particular, activation of calcium- and voltage-gated potassium channels of large conductance (BK channels) results in outward current that shifts the membrane potential toward more negative values, triggering a negative feed-back loop on depolarization-induced calcium influx and SM contraction. In this short review, we first present the molecular basis of vascular smooth muscle BK channels and the role of subunit composition and trafficking in the regulation of myogenic tone and vascular contractility. BK channel modulation by endogenous signaling molecules, and paracrine and endocrine mediators follows. Lastly, we describe the functional changes in smooth muscle BK channels that contribute to, or are triggered by, common physiological conditions and pathologies, including obesity, diabetes, and systemic hypertension.
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Affiliation(s)
- Alex M Dopico
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St., Memphis, TN, 38163, USA.
| | - Anna N Bukiya
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St., Memphis, TN, 38163, USA
| | - Jonathan H Jaggar
- Department of Physiology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, USA
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12
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The Slo(w) path to identifying the mitochondrial channels responsible for ischemic protection. Biochem J 2017; 474:2067-2094. [PMID: 28600454 DOI: 10.1042/bcj20160623] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 02/10/2017] [Accepted: 02/13/2017] [Indexed: 12/19/2022]
Abstract
Mitochondria play an important role in tissue ischemia and reperfusion (IR) injury, with energetic failure and the opening of the mitochondrial permeability transition pore being the major causes of IR-induced cell death. Thus, mitochondria are an appropriate focus for strategies to protect against IR injury. Two widely studied paradigms of IR protection, particularly in the field of cardiac IR, are ischemic preconditioning (IPC) and volatile anesthetic preconditioning (APC). While the molecular mechanisms recruited by these protective paradigms are not fully elucidated, a commonality is the involvement of mitochondrial K+ channel opening. In the case of IPC, research has focused on a mitochondrial ATP-sensitive K+ channel (mitoKATP), but, despite recent progress, the molecular identity of this channel remains a subject of contention. In the case of APC, early research suggested the existence of a mitochondrial large-conductance K+ (BK, big conductance of potassium) channel encoded by the Kcnma1 gene, although more recent work has shown that the channel that underlies APC is in fact encoded by Kcnt2 In this review, we discuss both the pharmacologic and genetic evidence for the existence and identity of mitochondrial K+ channels, and the role of these channels both in IR protection and in regulating normal mitochondrial function.
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13
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Detweiler ND, Song L, McClenahan SJ, Versluis RJ, Kharade SV, Kurten RC, Rhee SW, Rusch NJ. BK channels in rat and human pulmonary smooth muscle cells are BKα-β 1 functional complexes lacking the oxygen-sensitive stress axis regulated exon insert. Pulm Circ 2017; 6:563-575. [PMID: 28090300 DOI: 10.1086/688838] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
A loss of K+ efflux in pulmonary arterial smooth muscle cells (PASMCs) contributes to abnormal vasoconstriction and PASMC proliferation during pulmonary hypertension (PH). Activation of high-conductance Ca2+-activated (BK) channels represents a therapeutic strategy to restore K+ efflux to the affected PASMCs. However, the properties of BK channels in PASMCs-including sensitivity to BK channel openers (BKCOs)-are poorly defined. The goal of this study was to compare the properties of BK channels between PASMCs of normoxic (N) and chronic hypoxic (CH) rats and then explore key findings in human PASMCs. Polymerase chain reaction results revealed that 94.3% of transcripts encoding BKα pore proteins in PASMCs from N rats represent splice variants lacking the stress axis regulated exon insert, which confers oxygen sensitivity. Subsequent patch-clamp recordings from inside-out (I-O) patches confirmed a dense population of BK channels insensitive to hypoxia. The BK channels were highly activated by intracellular Ca2+ and the BKCO lithocholate; these responses require BKα-β1 subunit coupling. PASMCs of CH rats with established PH exhibited a profound overabundance of the dominant oxygen-insensitive BKα variant. Importantly, human BK (hBK) channels in PASMCs from human donor lungs also represented the oxygen-insensitive BKα variant activated by BKCOs. The hBK channels showed significantly enhanced Ca2+ sensitivity compared with rat BK channels. We conclude that rat BK and hBK channels in PASMCs are oxygen-insensitive BKα-β1 complexes highly sensitive to Ca2+ and the BKCO lithocholate. BK channels are overexpressed in PASMCs of a rat model of PH and may provide an abundant target for BKCOs designed to restore K+ efflux.
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Affiliation(s)
- Neil D Detweiler
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Li Song
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Samantha J McClenahan
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Rachel J Versluis
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Sujay V Kharade
- Department of Anesthesiology, School of Medicine, Vanderbilt University, Nashville, Tennessee, USA
| | - Richard C Kurten
- Department of Physiology and Biophysics and Department of Pediatrics, College of Medicine, University of Arkansas for Medical Sciences, Arkansas Children's Hospital Research Institute, Little Rock, Arkansas, USA
| | - Sung W Rhee
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Nancy J Rusch
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
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14
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Abstract
Large conductance Ca(2+)- and voltage-activated K(+) (BK) channels are widely distributed in the postnatal central nervous system (CNS). BK channels play a pleiotropic role in regulating the activity of brain and spinal cord neural circuits by providing a negative feedback mechanism for local increases in intracellular Ca(2+) concentrations. In neurons, they regulate the timing and duration of K(+) influx such that they can either increase or decrease firing depending on the cellular context, and they can suppress neurotransmitter release from presynaptic terminals. In addition, BK channels located in astrocytes and arterial myocytes modulate cerebral blood flow. Not surprisingly, both loss and gain of BK channel function have been associated with CNS disorders such as epilepsy, ataxia, mental retardation, and chronic pain. On the other hand, the neuroprotective role played by BK channels in a number of pathological situations could potentially be leveraged to correct neurological dysfunction.
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15
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Shipston MJ, Tian L. Posttranscriptional and Posttranslational Regulation of BK Channels. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:91-126. [PMID: 27238262 DOI: 10.1016/bs.irn.2016.02.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Large conductance calcium- and voltage-activated potassium (BK) channels are ubiquitously expressed and play an important role in the regulation of an eclectic array of physiological processes. Their diverse functional role requires channels with a wide variety of properties even though the pore-forming α-subunit is encoded by a single gene, KCNMA1. To achieve this, BK channels exploit some of the most fundamental posttranscriptional and posttranslational mechanisms that allow proteomic diversity to be generated from a single gene. These include mechanisms that diversify mRNA variants and abundance such as alternative pre-mRNA splicing, editing, and control by miRNA. The BK channel is also subject to a diverse array of posttranslational modifications including protein phosphorylation, lipidation, glycosylation, and ubiquitination to control the number, properties, and regulation of BK channels in specific cell types. Importantly, "cross talk" between these posttranscriptional and posttranslational modifications typically converge on disordered domains of the BK channel α-subunit. This allows both wide physiological diversity to be generated and a diversity of mechanisms to allow conditional regulation of BK channels and is emerging as an important determinant of BK channel function in health and disease.
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Affiliation(s)
- M J Shipston
- Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom.
| | - L Tian
- Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom
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16
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Gallego-Martin T, Agapito T, Ramirez M, Olea E, Yubero S, Rocher A, Gomez-Niño A, Obeso A, Gonzalez C. Experimental Observations on the Biological Significance of Hydrogen Sulfide in Carotid Body Chemoreception. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 860:9-16. [PMID: 26303462 DOI: 10.1007/978-3-319-18440-1_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The cascade of transduction of hypoxia and hypercapnia, the natural stimuli to chemoreceptor cells, is incompletely understood. A particular gap in that knowledge is the role played by second messengers, or in a most ample term, of modulators. A recently described modulator of chemoreceptor cell responses is the gaseous transmitter hydrogen sulfide, which has been proposed as a specific activator of the hypoxic responses in the carotid body, both at the level of the chemoreceptor cell response or at the level of the global output of the organ. Since sulfide behaves in this regard as cAMP, we explored the possibility that sulfide effects were mediated by the more classical messenger. Data indicate that exogenous and endogenous sulfide inhibits adenyl cyclase finding additionally that inhibition of adenylyl cyclase does not modify chemoreceptor cell responses elicited by sulfide. We have also observed that transient receptor potential cation channels A1 (TRPA1) are not regulated by sulfide in chemoreceptor cells.
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Affiliation(s)
- T Gallego-Martin
- Department of Biochemistry, Molecular Biology and Physiology, Medicine School, University of Valladolid and IBGM/CSIC, Valladolid, Spain,
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17
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Ramos Gomes F, Romaniello V, Sánchez A, Weber C, Narayanan P, Psol M, Pardo LA. Alternatively Spliced Isoforms of KV10.1 Potassium Channels Modulate Channel Properties and Can Activate Cyclin-dependent Kinase in Xenopus Oocytes. J Biol Chem 2015; 290:30351-65. [PMID: 26518875 PMCID: PMC4683259 DOI: 10.1074/jbc.m115.668749] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Indexed: 12/18/2022] Open
Abstract
KV10.1 is a voltage-gated potassium channel expressed selectively in the mammalian brain but also aberrantly in cancer cells. In this study we identified short splice variants of KV10.1 resulting from exon-skipping events (E65 and E70) in human brain and cancer cell lines. The presence of the variants was confirmed by Northern blot and RNase protection assays. Both variants completely lacked the transmembrane domains of the channel and produced cytoplasmic proteins without channel function. In a reconstituted system, both variants co-precipitated with the full-length channel and induced a robust down-regulation of KV10.1 current when co-expressed with the full-length form, but their effect was mechanistically different. E65 required a tetramerization domain and induced a reduction in the overall expression of full-length KV10.1, whereas E70 mainly affected its glycosylation pattern. E65 triggered the activation of cyclin-dependent kinases in Xenopus laevis oocytes, suggesting a role in cell cycle control. Our observations highlight the relevance of noncanonical functions for the oncogenicity of KV10.1, which need to be considered when ion channels are targeted for cancer therapy.
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Affiliation(s)
| | - Vincenzo Romaniello
- the Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
| | - Araceli Sánchez
- the Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
| | - Claudia Weber
- From the Department of Molecular Biology of Neuronal Signals and
| | | | - Maryna Psol
- From the Department of Molecular Biology of Neuronal Signals and
| | - Luis A Pardo
- the Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany
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18
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Sforna L, Cenciarini M, Belia S, D'Adamo MC, Pessia M, Franciolini F, Catacuzzeno L. The role of ion channels in the hypoxia-induced aggressiveness of glioblastoma. Front Cell Neurosci 2015; 8:467. [PMID: 25642170 PMCID: PMC4295544 DOI: 10.3389/fncel.2014.00467] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 12/24/2014] [Indexed: 12/16/2022] Open
Abstract
The malignancy of glioblastoma multiform (GBM), the most common and aggressive form of human brain tumors, strongly correlates with the presence of hypoxic areas, but the mechanisms controlling the hypoxia-induced aggressiveness are still unclear. GBM cells express a number of ion channels whose activity supports cell volume changes and increases in the cytosolic Ca2+ concentration, ultimately leading to cell proliferation, migration or death. In several cell types it has previously been shown that low oxygen levels regulate the expression and activity of these channels, and more recent data indicate that this also occurs in GBM cells. Based on these findings, it may be hypothesized that the modulation of ion channel activity or expression by the hypoxic environment may participate in the acquisition of the aggressive phenotype observed in GBM cells residing in a hypoxic environment. If this hypothesis will be confirmed, the use of available ion channels modulators may be considered for implementing novel therapeutic strategies against these tumors.
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Affiliation(s)
- Luigi Sforna
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Marta Cenciarini
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Silvia Belia
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Maria Cristina D'Adamo
- Faculty of Medicine, Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Mauro Pessia
- Faculty of Medicine, Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Fabio Franciolini
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Luigi Catacuzzeno
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
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19
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McLeod J, Leempoels J, Peng S, Dax S, Myers L, Golder F. GAL-021, a new intravenous BK Ca -channel blocker, is well tolerated and stimulates ventilation in healthy volunteers. Br J Anaesth 2014; 113:875-83. [DOI: 10.1093/bja/aeu182] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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20
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Tano JY, Gollasch M. Calcium-activated potassium channels in ischemia reperfusion: a brief update. Front Physiol 2014; 5:381. [PMID: 25339909 PMCID: PMC4186282 DOI: 10.3389/fphys.2014.00381] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 09/13/2014] [Indexed: 12/24/2022] Open
Abstract
Ischemia and reperfusion (IR) injury constitutes one of the major causes of cardiovascular morbidity and mortality. The discovery of new therapies to block/mediate the effects of IR is therefore an important goal in the biomedical sciences. Dysfunction associated with IR involves modification of calcium-activated potassium channels (KCa) through different mechanisms, which are still under study. Respectively, the KCa family, major contributors to plasma membrane calcium influx in cells and essential players in the regulation of the vascular tone are interesting candidates. This family is divided into two groups including the large conductance (BKCa) and the small/intermediate conductance (SKCa/IKCa) K(+) channels. In the heart and brain, these channels have been described to offer protection against IR injury. BKCa and SKCa channels deserve special attention since new data demonstrate that these channels are also expressed in mitochondria. More studies are however needed to fully determine their potential use as therapeutic targets.
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Affiliation(s)
- Jean-Yves Tano
- Experimental and Clinical Research Center, Charité University Medicine - Max Delbrück Center (MDC) for Molecular Medicine Berlin, Germany ; Nephrology/Intensive Care Section, Charité University Medicine Berlin, Germany
| | - Maik Gollasch
- Experimental and Clinical Research Center, Charité University Medicine - Max Delbrück Center (MDC) for Molecular Medicine Berlin, Germany ; Nephrology/Intensive Care Section, Charité University Medicine Berlin, Germany
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21
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Palmitoylation of STREX domain confers cerebroside sensitivity to the BKCa channel. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2451-9. [DOI: 10.1016/j.bbamem.2014.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 05/15/2014] [Accepted: 06/09/2014] [Indexed: 11/19/2022]
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22
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Abstract
Over the last decades, cardiovascular disease has become the primary cause of death in the Western world, and this trend is expanding throughout the world. In particular, atherosclerosis and the subsequent vessel obliterations are the primary cause of ischemic disease (stroke and coronary heart disease). Excess calcium influx into the cells is one of the major pathophysiological mechanisms important for ischemic injury in the brain and heart in humans. The large-conductance calcium-activated K+ channels (BK) are thus interesting candidates to protect against excess calcium influx and the events leading to ischemic injury. Indeed, the mitochondrial BK channels (mitoBK) have recently been shown to play a protective function against ischemia-reperfusion injury both in vitro and in animal models, although the exact mechanism of this protection is still under scrutiny. In addition, in both the plasma membrane and mitochondrial BK channel, the α-subunit itself is sensitive to hypoxia. This sensitivity is tissue specific and conferred by a highly conserved motif within an alternatively spliced cysteine-rich insert (STREX) in the intracellular C terminus of the channel. This review describes recent developments of the increasing relevance of BK channels in hypoxia and ischemia-reperfusion injury.
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Affiliation(s)
- Jean-Yves Tano
- Experimental and Clinical Research Center (a Joint Institution Between the Charité University Medicine and Max Delbrück Center for Molecular Medicine), Berlin-Buch, Germany; and Nephrology/Intensive Care Section, Charité Campus Virchow, Berlin, Germany
| | - Maik Gollasch
- Experimental and Clinical Research Center (a Joint Institution Between the Charité University Medicine and Max Delbrück Center for Molecular Medicine), Berlin-Buch, Germany; and Nephrology/Intensive Care Section, Charité Campus Virchow, Berlin, Germany
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23
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van der Schier R, Roozekrans M, van Velzen M, Dahan A, Niesters M. Opioid-induced respiratory depression: reversal by non-opioid drugs. F1000PRIME REPORTS 2014; 6:79. [PMID: 25343036 PMCID: PMC4173639 DOI: 10.12703/p6-79] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The human body is critically dependent on the ventilatory control system for adequate uptake of oxygen and removal of carbon dioxide (CO2). Potent opioid analgesics, through their actions on μ-opioid receptor (MOR) expressed on respiratory neurons in the brainstem, depress ventilation. Opioid-induced respiratory depression (OIRD) is potentially life threatening and the cause of substantial morbidity and mortality. One possible way of prevention of OIRD is by adding a respiratory stimulant to the opioid treatment, which through activation of non-opioidergic pathways will excite breathing and consequently will offset OIRD and should not affect analgesia. Various new respiratory stimulants are currently under investigation including (a) potassium channel blockers acting at the carotid bodies, and (b) ampakines and (c) serotonin receptor agonists acting within the brainstem. (a) GAL-021 targets BKCa-channels. Initial animal and human experimental evidence indicates that this potassium channel blocker is a potent respiratory stimulant that reverses OIRD without affecting antinociception. GAL021 is safe and better tolerated than the older K(+)-channel blocker doxapram and more efficacious in its effect on respiration. (b) Ampakines modulate glutamatergic respiratory neurons in brainstem respiratory centers. Various ampakines have been studied showing their ability to increase respiratory drive during OIRD by increasing respiratory rate. Currently, CX717 is the most promising ampakine for use in humans as it is safe and does not affect opioid analgesia. (c) While animal studies show that serotonin receptor agonists increase respiratory drive via activation of serotonin receptors in brainstem respiratory centers, human studies are without success. Further clinical studies are required to improve our care of patients that are treated with potent opioid analgesics. The use of non-opioid adjuvants may reduce the probability of OIRD but does never relieve us of our duty to continuously monitor these patients, irrespective whether they are treated in-house or in an ambulatory setting.
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Affiliation(s)
- Rutger van der Schier
- Department of Anesthesiology, Anesthesia & Pain Research Unit, Leiden University Medical CenterBuilding 1, Postzone P05-Q, P.O. Box 9600, 2300 RC LeidenThe Netherlands
| | - Margot Roozekrans
- Department of Anesthesiology, Anesthesia & Pain Research Unit, Leiden University Medical CenterBuilding 1, Postzone P05-Q, P.O. Box 9600, 2300 RC LeidenThe Netherlands
| | - Monique van Velzen
- Department of Anesthesiology, Anesthesia & Pain Research Unit, Leiden University Medical CenterBuilding 1, Postzone P05-Q, P.O. Box 9600, 2300 RC LeidenThe Netherlands
| | - Albert Dahan
- Department of Anesthesiology, Anesthesia & Pain Research Unit, Leiden University Medical CenterBuilding 1, Postzone P05-Q, P.O. Box 9600, 2300 RC LeidenThe Netherlands
| | - Marieke Niesters
- Department of Anesthesiology, Anesthesia & Pain Research Unit, Leiden University Medical CenterBuilding 1, Postzone P05-Q, P.O. Box 9600, 2300 RC LeidenThe Netherlands
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24
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Two Studies on Reversal of Opioid-induced Respiratory Depression by BK-channel Blocker GAL021 in Human Volunteers. Anesthesiology 2014; 121:459-68. [DOI: 10.1097/aln.0000000000000367] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Abstract
Background:
Opioid-induced respiratory depression is potentially lethal. GAL021 is a calcium-activated potassium (BKCa) channel blocker that causes reversal of opioid-induced respiratory depression in animals due to a stimulatory effect on ventilation at the carotid bodies. To assess in humans whether GAL021 stimulates breathing in established opioid-induced respiratory depression and to evaluate its safety, a proof-of-concept double-blind randomized controlled crossover study on isohypercapnic ventilation (study 1) and subsequent double-blind exploratory study on poikilocapnic ventilation and nonrespiratory end points (study 2) was performed.
Methods:
In study 1, intravenous low- and high-dose GAL021 and placebo were administrated on top of low- and high-dose alfentanil-induced respiratory depression in 12 healthy male volunteers on two separate occasions. In study 2, the effect of GAL021/placebo on poikilocapnic ventilation, analgesia, and sedation were explored in eight male volunteers. Data are mean difference between GAL021 and placebo (95% CI).
Results:
Study 1: Under isohypercapnic conditions, a separation between GAL021 and placebo on minute ventilation was observed by 6.1 (3.6 to 8.6) l/min (P < 0.01) and 3.6 (1.5 to 5.7) l/min (P < 0.01) at low-dose alfentanil plus high-dose GAL021 and high-dose-alfentanil plus high-dose GAL021, respectively. Study 2: Similar observations were made on poikilocapnic ventilation and arterial pCO2. GAL021 had no effect on alfentanil-induced sedation, antinociception and no safety issues or hemodynamic effects became apparent.
Conclusion:
GAL021 produces respiratory stimulatory effects during opioid-induced respiratory depression with containment of opioid-analgesia and without any further increase of sedation. Further studies are needed to confirm these preliminary data.
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25
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Abstract
SIGNIFICANCE Voltage-gated K+ channels are a large family of K+-selective ion channel protein complexes that open on membrane depolarization. These K+ channels are expressed in diverse tissues and their function is vital for numerous physiological processes, in particular of neurons and muscle cells. Potentially reversible oxidative regulation of voltage-gated K+ channels by reactive species such as reactive oxygen species (ROS) represents a contributing mechanism of normal cellular plasticity and may play important roles in diverse pathologies including neurodegenerative diseases. RECENT ADVANCES Studies using various protocols of oxidative modification, site-directed mutagenesis, and structural and kinetic modeling provide a broader phenomenology and emerging mechanistic insights. CRITICAL ISSUES Physicochemical mechanisms of the functional consequences of oxidative modifications of voltage-gated K+ channels are only beginning to be revealed. In vivo documentation of oxidative modifications of specific amino-acid residues of various voltage-gated K+ channel proteins, including the target specificity issue, is largely absent. FUTURE DIRECTIONS High-resolution chemical and proteomic analysis of ion channel proteins with respect to oxidative modification combined with ongoing studies on channel structure and function will provide a better understanding of how the function of voltage-gated K+ channels is tuned by ROS and the corresponding reducing enzymes to meet cellular needs.
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Affiliation(s)
- Nirakar Sahoo
- 1 Department of Biophysics, Center for Molecular Biomedicine, Friedrich Schiller University Jena and Jena University Hospital , Jena, Germany
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26
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Shipston MJ. S-acylation dependent post-translational cross-talk regulates large conductance calcium- and voltage- activated potassium (BK) channels. Front Physiol 2014; 5:281. [PMID: 25140154 PMCID: PMC4122160 DOI: 10.3389/fphys.2014.00281] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 07/09/2014] [Indexed: 01/14/2023] Open
Abstract
Mechanisms that control surface expression and/or activity of large conductance calcium-activated potassium (BK) channels are important determinants of their (patho)physiological function. Indeed, BK channel dysfunction is associated with major human disorders ranging from epilepsy to hypertension and obesity. S-acylation (S-palmitoylation) represents a major reversible, post-translational modification controlling the properties and function of many proteins including ion channels. Recent evidence reveals that both pore-forming and regulatory subunits of BK channels are S-acylated and control channel trafficking and regulation by AGC-family protein kinases. The pore-forming α-subunit is S-acylated at two distinct sites within the N- and C-terminus, each site being regulated by different palmitoyl acyl transferases (zDHHCs) and acyl thioesterases (APTs). S-acylation of the N-terminus controls channel trafficking and surface expression whereas S-acylation of the C-terminal domain determines regulation of channel activity by AGC-family protein kinases. S-acylation of the regulatory β4-subunit controls ER exit and surface expression of BK channels but does not affect ion channel kinetics at the plasma membrane. Furthermore, a significant number of previously identified BK-channel interacting proteins have been shown, or are predicted to be, S-acylated. Thus, the BK channel multi-molecular signaling complex may be dynamically regulated by this fundamental post-translational modification and thus S-acylation likely represents an important determinant of BK channel physiology in health and disease.
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Affiliation(s)
- Michael J Shipston
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh Edinburgh, UK
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27
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Environmental remodelling of GABAergic and glutamatergic neurotransmission: Rise of the anoxia-tolerant turtle brain. J Therm Biol 2014; 44:85-92. [DOI: 10.1016/j.jtherbio.2014.01.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 01/09/2014] [Accepted: 01/14/2014] [Indexed: 11/23/2022]
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28
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Waite SL, Gandhi SV, Khan RN, Chapman NR. The effect of trichostatin-A and tumor necrosis factor on expression of splice variants of the MaxiK and L-type channels in human myometrium. Front Physiol 2014; 5:261. [PMID: 25076912 PMCID: PMC4097961 DOI: 10.3389/fphys.2014.00261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 06/20/2014] [Indexed: 01/30/2023] Open
Abstract
The onset of human parturition is associated with up-regulation of pro-inflammatory cytokines including tumor necrosis factor (TNF) as well as changes in ion flux, principally Ca2+ and K+, across the myometrial myocytes membrane. Elevation of intra-cellular Ca2+ from the sarcoplasmic reticulum opens L-type Ca2+ channels (LTCCs); in turn this increased calcium level activates MaxiK channels leading to relaxation. While the nature of how this cross-talk is governed remains unclear, our previous work demonstrated that the pro-inflammatory cytokine, TNF, and the histone deacetylase inhibitor, Trichostatin-A (TSA), exerted opposing effects on the expression of the pro-quiescent Gαs gene in human myometrial cells. Consequently, in this study we demonstrate that the different channel splice variants for both MaxiK and LTCC are expressed in primary myometrial myocytes. MaxiK mRNA expression was sensitive to TSA stimulation, this causing repression of the M1, M3, and M4 splice variants. A small but not statistically significantly increase in MaxiK expression was also seen in response to TNF. In contrast to this, expression of LTCC splice variants was seen to be influenced by both TNF and TSA. TNF induced overall increase in total LTCC expression while TSA stimulated a dual effect: causing induction of LTCC exon 8 expression but repressing expression of other LTCC splice variants including that encoding exons 30, 31, 33, and 34, exons 30–34 and exons 40–43. The significance of these observations is discussed herein.
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Affiliation(s)
- Sarah L Waite
- Academic Unit of Reproductive and Developmental Medicine, Department of Human Metabolism, University of Sheffield Sheffield, UK
| | - Saurabh V Gandhi
- Department of Obstetrics and Gynaecology, Sheffield Teaching Hospitals NHS Foundation Trust Sheffield, UK
| | - Raheela N Khan
- Division of Medical Sciences and Graduate Entry Medicine, School of Medicine, Royal Derby Hospital, University of Nottingham Derby, UK
| | - Neil R Chapman
- Academic Unit of Reproductive and Developmental Medicine, Department of Human Metabolism, University of Sheffield Sheffield, UK
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29
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Gu XQ, Pamenter ME, Siemen D, Sun X, Haddad GG. Mitochondrial but not plasmalemmal BK channels are hypoxia-sensitive in human glioma. Glia 2014; 62:504-13. [PMID: 24446243 DOI: 10.1002/glia.22620] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 12/09/2013] [Accepted: 12/10/2013] [Indexed: 11/05/2022]
Abstract
Tumor cells are resistant to hypoxia but the underlying mechanism(s) of this tolerance remain poorly understood. In healthy brain cells, plasmalemmal Ca(2+)-activated K(+) channels ((plasma)BK) function as oxygen sensors and close under hypoxic conditions. Similarly, BK channels in the mitochondrial inner membrane ((mito)BK) are also hypoxia sensitive and regulate reactive oxygen species production and also permeability transition pore formation. Both channel populations are therefore well situated to mediate cellular responses to hypoxia. In tumors, BK channel expression increases with malignancy, suggesting these channels contribute to tumor growth; therefore, we hypothesized that the sensitivity of (plasma)BK and/or (mito)BK to hypoxia differs between glioma and healthy brain cells. To test this, we examined the electrophysiological properties of (plasma)BK and (mito)BK from a human glioma cell line during normoxia and hypoxia. We observed single channel activities in whole cells and isolated mitoplasts with slope conductance of 199 ± 8 and 278 ± 10 pA, respectively. These currents were Ca(2+)- and voltage-dependent, and were inhibited by the BK channel antagonist charybdotoxin (0.1 μM). (plasma)BK could only be activated at membrane potentials >+40 mV and had a low open probability (NPo) that was unchanged by hypoxia. Conversely, (mito)BK were active across a range of membrane potentials (-40 to +40 mV) and their NPo increased during hypoxia. Activating (plasma)BK, but not (mito)BK induced cell death and this effect was enhanced during hypoxia. We conclude that unlike in healthy brain cells, glioma (mito)BK channels, but not (plasma)BK channels are oxygen sensitive.
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Affiliation(s)
- Xiang Q Gu
- Section of Respiratory Medicine, Department of Pediatrics, University of California San Diego, La Jolla, California
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30
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Regulation of large conductance calcium- and voltage-activated potassium (BK) channels by S-palmitoylation. Biochem Soc Trans 2013; 41:67-71. [PMID: 23356260 DOI: 10.1042/bst20120226] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BK (large conductance calcium- and voltage-activated potassium) channels are important determinants of physiological control in the nervous, endocrine and vascular systems with channel dysfunction associated with major disorders ranging from epilepsy to hypertension and obesity. Thus the mechanisms that control channel surface expression and/or activity are important determinants of their (patho)physiological function. BK channels are S-acylated (palmitoylated) at two distinct sites within the N- and C-terminus of the pore-forming α-subunit. Palmitoylation of the N-terminus controls channel trafficking and surface expression whereas palmitoylation of the C-terminal domain determines regulation of channel activity by AGC-family protein kinases. Recent studies are beginning to reveal mechanistic insights into how palmitoylation controls channel trafficking and cross-talk with phosphorylation-dependent signalling pathways. Intriguingly, each site of palmitoylation is regulated by distinct zDHHCs (palmitoyl acyltransferases) and APTs (acyl thioesterases). This supports that different mechanisms may control substrate specificity by zDHHCs and APTs even within the same target protein. As palmitoylation is dynamically regulated, this fundamental post-translational modification represents an important determinant of BK channel physiology in health and disease.
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31
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Chen M, Sun HY, Hu P, Wang CF, Li BX, Li SJ, Li JJ, Tan HY, Gao TM. Activation of BKCa Channels Mediates Hippocampal Neuronal Death After Reoxygenation and Reperfusion. Mol Neurobiol 2013; 48:794-807. [DOI: 10.1007/s12035-013-8467-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Accepted: 04/26/2013] [Indexed: 11/29/2022]
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Kelemen O, Convertini P, Zhang Z, Wen Y, Shen M, Falaleeva M, Stamm S. Function of alternative splicing. Gene 2013; 514:1-30. [PMID: 22909801 PMCID: PMC5632952 DOI: 10.1016/j.gene.2012.07.083] [Citation(s) in RCA: 504] [Impact Index Per Article: 45.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/21/2012] [Accepted: 07/30/2012] [Indexed: 12/15/2022]
Abstract
Almost all polymerase II transcripts undergo alternative pre-mRNA splicing. Here, we review the functions of alternative splicing events that have been experimentally determined. The overall function of alternative splicing is to increase the diversity of mRNAs expressed from the genome. Alternative splicing changes proteins encoded by mRNAs, which has profound functional effects. Experimental analysis of these protein isoforms showed that alternative splicing regulates binding between proteins, between proteins and nucleic acids as well as between proteins and membranes. Alternative splicing regulates the localization of proteins, their enzymatic properties and their interaction with ligands. In most cases, changes caused by individual splicing isoforms are small. However, cells typically coordinate numerous changes in 'splicing programs', which can have strong effects on cell proliferation, cell survival and properties of the nervous system. Due to its widespread usage and molecular versatility, alternative splicing emerges as a central element in gene regulation that interferes with almost every biological function analyzed.
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Affiliation(s)
- Olga Kelemen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Paolo Convertini
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Zhaiyi Zhang
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Yuan Wen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Manli Shen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Marina Falaleeva
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Stefan Stamm
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
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Kim D. K(+) channels in O(2) sensing and postnatal development of carotid body glomus cell response to hypoxia. Respir Physiol Neurobiol 2012; 185:44-56. [PMID: 22801091 DOI: 10.1016/j.resp.2012.07.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Revised: 07/06/2012] [Accepted: 07/09/2012] [Indexed: 12/25/2022]
Abstract
The sensitivity of carotid body chemoreceptors to hypoxia is low just after birth and increases over the first few weeks of the postnatal period. At present, it is believed that the hypoxia-induced excitation of carotid body glomus cells begins with the inhibition of the outward K(+) current via one or more O(2) sensors. Although the nature of the O(2) sensors and their signals that inhibit the K(+) current are not well defined, studies suggest that the postnatal maturation of the glomus cell response to hypoxia is largely due to the increased sensitivity of K(+) channels to hypoxia. As K(V), BK and TASK channels that are O(2)-sensitive contribute to the K(+) current, it is important to identify the O(2) sensor and the signaling molecule for each of these K(+) channels. Various O(2) sensors (mitochondrial hemeprotein, hemeoxygenase-2, NADPH oxidase) and associated signals have been proposed to mediate the inhibition of K(+) channels by hypoxia. Studies suggest that a mitochondrial hemeprotein is likely to serve as an O(2) sensor for K(+) channels, particularly for TASK, and that multiple signals may be involved. Thus, changes in the sensitivity of the mitochondrial O(2) sensor to hypoxia, the sensitivity of K(+) channels to signals generated by mitochondria, and/or the expression levels of K(+) channels are likely to account for the postnatal maturation of O(2) sensing by glomus cells.
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Affiliation(s)
- Donghee Kim
- Department of Physiology and Biophysics, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, United States.
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Dospinescu C, Widmer H, Rowe I, Wainwright C, Cruickshank SF. Hypoxia sensitivity of a voltage-gated potassium current in porcine intrapulmonary vein smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2012; 303:L476-86. [PMID: 22773694 DOI: 10.1152/ajplung.00157.2012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypoxia contracts the pulmonary vein, but the underlying cellular effectors remain unclear. Utilizing contractile studies and whole cell patch-clamp electrophysiology, we report for the first time a hypoxia-sensitive K(+) current in porcine pulmonary vein smooth muscle cells (PVSMC). Hypoxia induced a transient contractile response that was 56 ± 7% of the control response (80 mM KCl). This contraction required extracellular Ca(2+) and was sensitive to Ca(2+) channel blockade. Blockade of K(+) channels by tetraethylammonium chloride (TEA) or 4-aminopyridine (4-AP) reversibly inhibited the hypoxia-mediated contraction. Single-isolated PVSMC (typically 159.1 ± 2.3 μm long) had mean resting membrane potentials (RMP) of -36 ± 4 mV with a mean membrane capacitance of 108 ± 3.5 pF. Whole cell patch-clamp recordings identified a rapidly activating, partially inactivating K(+) current (I(KH)) that was hypoxia, TEA, and 4-AP sensitive. I(KH) was insensitive to Penitrem A or glyburide in PVSMC and had a time to peak of 14.4 ± 3.3 ms and recovered in 67 ms following inactivation at +80 mV. Peak window current was -32 mV, suggesting that I(KH) may contribute to PVSMC RMP. The molecular identity of the potassium channel is not clear. However, RT-PCR, using porcine pulmonary artery and vein samples, identified Kv(1.5), Kv(2.1), and BK, with all three being more abundant in the PV. Both artery and vein expressed STREX, a highly conserved and hypoxia-sensitive BK channel variant. Taken together, our data support the hypothesis that hypoxic inhibition of I(KH) would contribute to hypoxic-induced contraction in PVSMC.
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Affiliation(s)
- Ciprian Dospinescu
- School of Pharmacy and Life Sciences, Robert Gordon Univ, Schoolhill, Aberdeen, Scotland UK
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35
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Mkrtchian S, Kåhlin J, Ebberyd A, Gonzalez C, Sanchez D, Balbir A, Kostuk EW, Shirahata M, Fagerlund MJ, Eriksson LI. The human carotid body transcriptome with focus on oxygen sensing and inflammation--a comparative analysis. J Physiol 2012; 590:3807-19. [PMID: 22615433 DOI: 10.1113/jphysiol.2012.231084] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The carotid body (CB) is the key oxygen sensing organ. While the expression of CB specific genes is relatively well studied in animals, corresponding data for the human CB are missing. In this study we used five surgically removed human CBs to characterize the CB transcriptome with microarray and PCR analyses, and compared the results with mice data. In silico approaches demonstrated a unique gene expression profile of the human and mouse CB transcriptomes and an unexpected upregulation of both human and mouse CB genes involved in the inflammatory response compared to brain and adrenal gland data. Human CBs express most of the genes previously proposed to be involved in oxygen sensing and signalling based on animal studies, including NOX2, AMPK, CSE and oxygen sensitive K+ channels. In the TASK subfamily of K+ channels, TASK-1 is expressed in human CBs, while TASK-3 and TASK-5 are absent, although we demonstrated both TASK-1 and TASK-3 in one of the mouse reference strains. Maxi-K was expressed exclusively as the spliced variant ZERO in the human CB. In summary, the human CB transcriptome shares important features with the mouse CB, but also differs significantly in the expression of a number of CB chemosensory genes. This study provides key information for future functional investigations on the human carotid body.
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Affiliation(s)
- Souren Mkrtchian
- Section for Anesthesiology and Intensive Care Medicine, Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
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36
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Zhang R, Sun H, Liao C, Yang H, Zhao B, Tian J, Dong S, Zhang Z, Jiao J. Chronic hypoxia in cultured human podocytes inhibits BKCa channels by upregulating its β4-subunit. Biochem Biophys Res Commun 2012; 420:505-10. [DOI: 10.1016/j.bbrc.2012.03.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Accepted: 03/07/2012] [Indexed: 01/30/2023]
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37
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Mittal M, Gu XQ, Pak O, Pamenter ME, Haag D, Fuchs DB, Schermuly RT, Ghofrani HA, Brandes RP, Seeger W, Grimminger F, Haddad GG, Weissmann N. Hypoxia induces Kv channel current inhibition by increased NADPH oxidase-derived reactive oxygen species. Free Radic Biol Med 2012; 52:1033-42. [PMID: 22222468 DOI: 10.1016/j.freeradbiomed.2011.12.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Revised: 11/23/2011] [Accepted: 12/03/2011] [Indexed: 10/24/2022]
Abstract
There is current discussion whether reactive oxygen species are up- or downregulated in the pulmonary circulation during hypoxia, from which sources (i.e., mitochondria or NADPH oxidases) they are derived, and what the downstream targets of ROS are. We recently showed that the NADPH oxidase homolog NOX4 is upregulated in hypoxia-induced pulmonary hypertension in mice and contributes to the vascular remodeling in pulmonary hypertension. We here tested the hypothesis that NOX4 regulates K(v) channels via an increased ROS formation after prolonged hypoxia. We showed that (1) NOX4 is upregulated in hypoxia-induced pulmonary hypertension in rats and isolated rat pulmonary arterial smooth muscle cells (PASMC) after 3days of hypoxia, and (2) that NOX4 is a major contributor to increased reactive oxygen species (ROS) after hypoxia. Our data indicate colocalization of K(v)1.5 and NOX4 in isolated PASMC. The NADPH oxidase inhibitor and ROS scavenger apocynin as well as NOX4 siRNA reversed the hypoxia-induced decrease in K(v) current density whereas the protein levels of the channels remain unaffected by siNOX4 treatment. Determination of cysteine oxidation revealed increased NOX4-mediated K(v)1.5 channel oxidation. We conclude that sustained hypoxia decreases K(v) channel currents by a direct effect of a NOX4-derived increase in ROS.
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Affiliation(s)
- Manish Mittal
- Excellence Cluster Cardio-Pulmonary System, University of Giessen Lung Center, Justus-Liebig-University, Medical Clinic II/V, Aulweg 130, Giessen 35392, Germany
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Intragenic alternative splicing coordination is essential for Caenorhabditis elegans slo-1 gene function. Proc Natl Acad Sci U S A 2011; 108:20790-5. [PMID: 22084100 DOI: 10.1073/pnas.1116712108] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Alternative splicing is critical for diversifying eukaryotic proteomes, but the rules governing and coordinating splicing events among multiple alternate splice sites within individual genes are not well understood. We developed a quantitative PCR-based strategy to quantify the expression of the 12 transcripts encoded by the Caenorhabditis elegans slo-1 gene, containing three alternate splice sites. Using conditional probability-based models, we show that splicing events are coordinated across these sites. Further, we identify a point mutation in an intron adjacent to one alternate splice site that disrupts alternative splicing at all three sites. This mutation leads to aberrant synaptic transmission at the neuromuscular junction. In a genomic survey, we found that a UAAAUC element disrupted by this mutation is enriched in introns flanking alternate exons in genes with multiple alternate splice sites. These results establish that proper coordination of intragenic alternative splicing is essential for normal physiology of slo-1 in vivo and identify putative specialized cis-regulatory elements that regulate the coordination of intragenic alternative splicing.
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39
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Alternatively spliced domains interact to regulate BK potassium channel gating. Proc Natl Acad Sci U S A 2011; 108:20784-9. [PMID: 22049343 DOI: 10.1073/pnas.1116795108] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Most human genes contain multiple alternative splice sites believed to extend the complexity and diversity of the proteome. However, little is known about how interactions among alternative exons regulate protein function. We used the Caenorhabditis elegans slo-1 large-conductance calcium and voltage-activated potassium (BK) channel gene, which contains three alternative splice sites (A, B, and C) and encodes at least 12 splice variants, to investigate the functional consequences of alternative splicing. These splice sites enable the insertion of exons encoding part of the regulator of K(+) conductance (RCK)1 Ca(2+) coordination domain (exons A1 and A2) and portions of the RCK1-RCK2 linker (exons B0, B1, B2, C0, and C1). Exons A1 and A2 are used in a mutually exclusive manner and are 67% identical. The other exons can extend the RCK1-RCK2 linker by up to 41 residues. Electrophysiological recordings of all isoforms show that the A1 and A2 exons regulate activation kinetics and Ca(2+) sensitivity, but only if alternate exons are inserted at site B or C. Thus, RCK1 interacts with the RCK1-RCK2 linker, and the effect of exon variation on gating depends on the combination of alternate exons present in each isoform.
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40
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Ross FA, Rafferty JN, Dallas ML, Ogunbayo O, Ikematsu N, McClafferty H, Tian L, Widmer H, Rowe ICM, Wyatt CN, Shipston MJ, Peers C, Hardie DG, Evans AM. Selective expression in carotid body type I cells of a single splice variant of the large conductance calcium- and voltage-activated potassium channel confers regulation by AMP-activated protein kinase. J Biol Chem 2011; 286:11929-36. [PMID: 21209098 PMCID: PMC3069395 DOI: 10.1074/jbc.m110.189779] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Inhibition of large conductance calcium-activated potassium (BKCa) channels mediates, in part, oxygen sensing by carotid body type I cells. However, BKCa channels remain active in cells that do not serve to monitor oxygen supply. Using a novel, bacterially derived AMP-activated protein kinase (AMPK), we show that AMPK phosphorylates and inhibits BKCa channels in a splice variant-specific manner. Inclusion of the stress-regulated exon within BKCa channel α subunits increased the stoichiometry of phosphorylation by AMPK when compared with channels lacking this exon. Surprisingly, however, the increased phosphorylation conferred by the stress-regulated exon abolished BKCa channel inhibition by AMPK. Point mutation of a single serine (Ser-657) within this exon reduced channel phosphorylation and restored channel inhibition by AMPK. Significantly, RT-PCR showed that rat carotid body type I cells express only the variant of BKCa that lacks the stress-regulated exon, and intracellular dialysis of bacterially expressed AMPK markedly attenuated BKCa currents in these cells. Conditional regulation of BKCa channel splice variants by AMPK may therefore determine the response of carotid body type I cells to hypoxia.
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Affiliation(s)
- Fiona A Ross
- College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, United Kingdom
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41
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Zhao HC, Agula H, Zhang W, Wang F, Sokabe M, Li LM. Membrane stretch and cytoplasmic Ca2+ independently modulate stretch-activated BK channel activity. J Biomech 2010; 43:3015-9. [DOI: 10.1016/j.jbiomech.2010.06.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 06/28/2010] [Accepted: 06/30/2010] [Indexed: 12/23/2022]
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42
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Poulsen AN, Jansen-Olesen I, Olesen J, Klaerke DA. Neuronal fast activating and meningeal silent modulatory BK channel splice variants cloned from rat. Pflugers Arch 2010; 461:65-75. [PMID: 20938677 DOI: 10.1007/s00424-010-0887-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 09/20/2010] [Accepted: 09/23/2010] [Indexed: 12/25/2022]
Abstract
The big conductance calcium-activated K(+) channel (BK) is involved in regulating neuron and smooth muscle cell excitability. Functional diversity of BK is generated by alpha-subunit splice variation and co-expression with beta subunits. Here, we present six different splice combinations cloned from rat brain or cerebral vascular/meningeal tissues, of which at least three variants were previously uncharacterized (X1, X2(92), and X2(188)). An additional variant was identified by polymerase chain reaction but not cloned. Expression in Xenopus oocytes showed that the brain-specific X1 variant displays reduced current, faster activation, and less voltage sensitivity than the insert-less Zero variant. Other cloned variants Strex and Slo27,3 showed slower activation than Zero. The X1 variant contains sequence inserts in the S1-S2 extracellular loop (8 aa), between intracellular domains RCK1 and RCK2 (4 aa at SS1) and upstream of the calcium "bowl" (27 aa at SS4). Two other truncated variants, X2(92) and X2(188), lacking the intracellular C-terminal (stop downstream of S6), were cloned from cerebral vascular/meningeal tissue. They appear non-functional as no current expression was observed, but the X2(92) appeared to slow the activation of the Zero variant when co-expressed. Positive protein expression of X2(92) was observed in oocytes by immunoblotting and fluorescence using a yellow fluorescent protein-tagged construct. The functional characteristics of the X1 variant may be important for a subpopulation of BK channels in the brain, while the "silent" truncated variants X2(92) and X2(188) may play a role as modulators of other BK channel variants in a way similar to well known beta subunits.
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Affiliation(s)
- Asser Nyander Poulsen
- Department of Animal and Veterinary Basic Sciences, Faculty of Life Sciences, University of Copenhagen, Groennegaardsvej 7, Frederiksberg C, Denmark.
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43
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Ermolinsky BS, Skinner F, Garcia I, Arshadmansab MF, Otalora LFP, Zarei MM, Garrido-Sanabria ER. Upregulation of STREX splice variant of the large conductance Ca2+-activated potassium (BK) channel in a rat model of mesial temporal lobe epilepsy. Neurosci Res 2010; 69:73-80. [PMID: 20933547 DOI: 10.1016/j.neures.2010.09.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2010] [Revised: 09/29/2010] [Accepted: 09/30/2010] [Indexed: 02/04/2023]
Abstract
Functional properties of large conductance Ca(2+) activated potassium (BK) channels are determined by complex alternative splicing of the Kcnma1 gene encoding the alpha pore-forming subunit. Inclusion of the STREX exon in a C-terminal splice site is dynamically regulated and confers enhanced Ca(2+) sensitivity and channel inhibition via cAMP-dependent phosphorylation. Here, we describe a real time quantitative PCR (qPCR) approach to investigate relative changes in the expression of STREX and ZERO splice variants using a newly designed set of probes and primers for TaqMan-based qPCR analysis of cDNA from the rat dentate gyrus at different time points following pilocarpine-induced status epilepticus. Reduction in Kcnma1 gene expression is associated with a relative increase of STREX splice variant. Relative expression of STREX variant mRNA was increased at 10 days and at more than 1 month following status epilepticus. The biological consequences of seizure-related changes in alternative splicing of Kcnma1 deserve additional investigation.
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Affiliation(s)
- Boris S Ermolinsky
- Department of Biological Sciences, University of Texas at Brownsville/Texas Southmost College, Brownsville, TX 78520, USA
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44
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Gonzalez C, Agapito MT, Rocher A, Gomez-Niño A, Rigual R, Castañeda J, Conde SV, Obeso A. A revisit to O2 sensing and transduction in the carotid body chemoreceptors in the context of reactive oxygen species biology. Respir Physiol Neurobiol 2010; 174:317-30. [PMID: 20833275 DOI: 10.1016/j.resp.2010.09.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2010] [Revised: 08/31/2010] [Accepted: 09/01/2010] [Indexed: 11/25/2022]
Abstract
Oxygen-sensing and transduction in purposeful responses in cells and organisms is of great physiological and medical interest. All animals, including humans, encounter in their lifespan many situations in which oxygen availability might be insufficient, whether acutely or chronically, physiologically or pathologically. Therefore to trace at the molecular level the sequence of events or steps connecting the oxygen deficit with the cell responses is of interest in itself as an achievement of science. In addition, it is also of great medical interest as such knowledge might facilitate the therapeutical approach to patients and to design strategies to minimize hypoxic damage. In our article we define the concepts of sensors and transducers, the steps of the hypoxic transduction cascade in the carotid body chemoreceptor cells and also discuss current models of oxygen- sensing (bioenergetic, biosynthetic and conformational) with their supportive and unsupportive data from updated literature. We envision oxygen-sensing in carotid body chemoreceptor cells as a process initiated at the level of plasma membrane and performed by a hemoprotein, which might be NOX4 or a hemoprotein not yet chemically identified. Upon oxygen-desaturation, the sensor would experience conformational changes allosterically transmitted to oxygen regulated K+ channels, the initial effectors in the transduction cascade. A decrease in their opening probability would produce cell depolarization, activation of voltage dependent calcium channels and release of neurotransmitters. Neurotransmitters would activate the nerve endings of the carotid body sensory nerve to convey the information of the hypoxic situation to the central nervous system that would command ventilation to fight hypoxia.
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Affiliation(s)
- C Gonzalez
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular y CIBER de Enfermedades Respiratorias, Universidad de Valladolid, Consejo Superior de Investigaciones Científicas e Instituto Carlos III, Facultad de Medicina, 47005 Valladolid, Spain.
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45
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Dryer SE, Reiser J. TRPC6 channels and their binding partners in podocytes: role in glomerular filtration and pathophysiology. Am J Physiol Renal Physiol 2010; 299:F689-701. [PMID: 20685822 DOI: 10.1152/ajprenal.00298.2010] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Loss or dysfunction of podocytes is a major cause of glomerular kidney disease. Several genetic forms of glomerular disease are caused by mutations in genes that encode structural elements of the slit diaphragm or the underlying cytoskeleton of podocyte foot processes. The recent discovery that gain-of-function mutations in Ca(2+)-permeable canonical transient receptor potential-6 channels (TRPC6) underlie a subset of familial forms of focal segmental glomerulosclerosis (FSGS) has focused attention on the basic cellular physiology of podocytes. Several recent studies have examined the role of Ca(2+) dynamics in normal podocyte function and their possible contributions to glomerular disease. This review summarizes the properties of TRPC6 and related channels, focusing on their permeation and gating properties, the nature of mutations associated with familial FSGS, and the role of TRPC channels in podocyte cell biology as well as in glomerular pathophysiology. TRPC6 interacts with several proteins in podocytes, including essential slit diaphragm proteins and mechanosensitive large-conductance Ca(2+)-activated K(+) channels. The signaling dynamics controlling ion channel function and localization in podocytes appear to be quite complex.
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Affiliation(s)
- Stuart E Dryer
- Dept. of Biology and Biochemistry, Univ. of Houston, 4800 Calhoun, Houston, TX 77204-5001, USA.
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46
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Millership JE, Heard C, Fearon IM, Bruce JIE. Differential Regulation of Calcium-Activated Potassium Channels by Dynamic Intracellular Calcium Signals. J Membr Biol 2010; 235:191-210. [DOI: 10.1007/s00232-010-9266-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2009] [Accepted: 05/14/2010] [Indexed: 01/08/2023]
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47
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Gurney AM, Joshi S, Manoury B. KCNQ potassium channels: new targets for pulmonary vasodilator drugs? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 661:405-17. [PMID: 20204745 DOI: 10.1007/978-1-60761-500-2_26] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Smooth muscle cells regulate the diameter of pulmonary arteries and the resistance to blood flow in the pulmonary circulation. These cells are normally relaxed to maintain low intrinsic vessel tone, but are contracted in pulmonary arterial hypertension (PAH). Potassium channels in the smooth muscle cell help to maintain low tone by polarising the membrane and preventing Ca(2+) influx through voltage-operated Ca(2+) channels. There is a loss of K(+) channel activity in PAH, so drugs that open K(+) channels are predicted to have a beneficial effect, provided their action can be restricted to the pulmonary circulation. Here we review the myriad of K(+) channels that are expressed in pulmonary arteries and suggest the roles that each might play in regulating pulmonary artery tone. We conclude that members of the KCNQ family of K(+) channels, the most recent K(+) channels to be discovered in pulmonary artery, may be a useful therapeutic target for the treatment of PAH. KCNQ channels appear to be preferentially expressed in pulmonary arteries and drugs that modulate their activity have potent effects on pulmonary artery tone.
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Affiliation(s)
- Alison M Gurney
- Faculty of Life Sciences, University of Manchester, Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT, UK, Alison.
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48
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Kemp PJ, Telezhkin V, Wilkinson WJ, Mears R, Hanmer SB, Gadeberg HC, Müller CT, Riccardi D, Brazier SP. Enzyme-Linked Oxygen Sensing by Potassium Channels. Ann N Y Acad Sci 2009; 1177:112-8. [DOI: 10.1111/j.1749-6632.2009.05025.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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49
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Abstract
Mitochondrial potassium channels are believed to contribute to cytoprotection of injured cardiac and neuronal tissues. The following potassium channels have been described in the inner mitochondrial membrane: the ATP-regulated potassium channel, the large conductance Ca(2+)-activated potassium channel, the voltage-gated Kv1.3 potassium channel, and the twin-pore domain TASK-3 potassium channel. The putative functional roles of these channels include changes in mitochondrial matrix volume, mitochondrial respiration, and membrane potential. In addition, the activity of these channels modulates the generation of reactive oxygen species by mitochondria. In this article, we discuss recent observations on three fundamental issues concerning mitochondrial potassium channels: (i) their molecular identity, (ii) their interaction with potassium channel openers and inhibitors, and (iii) their functional properties.
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Affiliation(s)
- Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Warsaw, Poland.
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50
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Hou S, Heinemann SH, Hoshi T. Modulation of BKCa channel gating by endogenous signaling molecules. Physiology (Bethesda) 2009; 24:26-35. [PMID: 19196649 DOI: 10.1152/physiol.00032.2008] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Large-conductance Ca(2+)- and voltage-activated K(+) (BK(Ca), MaxiK, or Slo1) channels are expressed in almost every tissue in our body and participate in many critical functions such as neuronal excitability, vascular tone regulation, and neurotransmitter release. The functional versatility of BK(Ca) channels owes in part to the availability of a spectacularly wide array of biological modulators of the channel function. In this review, we focus on modulation of BK(Ca) channels by small endogenous molecules, emphasizing their molecular mechanisms. The mechanistic information available from studies on the small naturally occurring modulators is expected to contribute to our understanding of the physiological and pathophysiological roles of BK(Ca) channels.
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Affiliation(s)
- Shangwei Hou
- Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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