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Mahapatra C, Kumar R. Biophysical Mechanisms of Vaginal Smooth Muscle Contraction: The Role of the Membrane Potential and Ion Channels. PATHOPHYSIOLOGY 2024; 31:225-243. [PMID: 38804298 PMCID: PMC11130850 DOI: 10.3390/pathophysiology31020018] [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: 03/26/2024] [Revised: 05/10/2024] [Accepted: 05/14/2024] [Indexed: 05/29/2024] Open
Abstract
The vagina is an essential component of the female reproductive system and is responsible for providing female sexual satisfaction. Vaginal smooth muscle contraction plays a crucial role in various physiological processes, including sexual arousal, childbirth, and urinary continence. In pathophysiological conditions, such as pelvic floor disorders, aberrations in vaginal smooth muscle function can lead to urinary incontinence and pelvic organ prolapse. A set of cellular and sub-cellular physiological mechanisms regulates the contractile properties of the vaginal smooth muscle cells. Calcium influx is a crucial determinant of smooth muscle contraction, facilitated through voltage-dependent calcium channels and calcium release from intracellular stores. Comprehensive reviews on smooth muscle biophysics are relatively scarce within the scientific literature, likely due to the complexity and specialized nature of the topic. The objective of this review is to provide a comprehensive description of alterations in the cellular physiology of vaginal smooth muscle contraction. The benefit associated with this particular approach is that conducting a comprehensive examination of the cellular mechanisms underlying contractile activation will enable the creation of more targeted therapeutic agents to control vaginal contraction disorders.
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Affiliation(s)
- Chitaranjan Mahapatra
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
- Paris Saclay Institute of Neuroscience, 91440 Saclay, France
| | - Ravinder Kumar
- Department of Pathology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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Ponnalagu D, Hamilton S, Sanghvi S, Antelo D, Schwieterman N, Hansra I, Xu X, Gao E, Edwards JC, Bansal SS, Wold LE, Terentyev D, Janssen PML, Hund TJ, Khan M, Kohut AR, Koch WJ, Singh H. CLIC4 localizes to mitochondrial-associated membranes and mediates cardioprotection. SCIENCE ADVANCES 2022; 8:eabo1244. [PMID: 36269835 PMCID: PMC9586484 DOI: 10.1126/sciadv.abo1244] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 08/25/2022] [Indexed: 06/12/2023]
Abstract
Mitochondrial-associated membranes (MAMs) are known to modulate organellar and cellular functions and can subsequently affect pathophysiology including myocardial ischemia-reperfusion (IR) injury. Thus, identifying molecular targets in MAMs that regulate the outcome of IR injury will hold a key to efficient therapeutics. Here, we found chloride intracellular channel protein (CLIC4) presence in MAMs of cardiomyocytes and demonstrate its role in modulating ER and mitochondrial calcium homeostasis under physiological and pathological conditions. In a murine model, loss of CLIC4 increased myocardial infarction and substantially reduced cardiac function after IR injury. CLIC4 null cardiomyocytes showed increased apoptosis and mitochondrial dysfunction upon hypoxia-reoxygenation injury in comparison to wild-type cardiomyocytes. Overall, our results indicate that MAM-CLIC4 is a key mediator of cellular response to IR injury and therefore may have a potential implication on other pathophysiological processes.
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Affiliation(s)
- Devasena Ponnalagu
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
| | - Shanna Hamilton
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
| | - Shridhar Sanghvi
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
| | - Diego Antelo
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
| | - Neill Schwieterman
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
- College of Nursing, The Ohio State University, Columbus, OH, USA
| | - Inderjot Hansra
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
| | - Xianyao Xu
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
- Departments of Biomedical Engineering and Internal Medicine, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
| | - Erhe Gao
- Center for Translational Medicine, Department of Pharmacology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - John C. Edwards
- Nephrology Division, Department of Internal Medicine, St. Louis University, St. Louis, MO, USA
| | - Shyam S. Bansal
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
| | - Loren E. Wold
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
- College of Nursing, The Ohio State University, Columbus, OH, USA
| | - Dmitry Terentyev
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
| | - Paul M. L. Janssen
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
| | - Thomas J. Hund
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
- Departments of Biomedical Engineering and Internal Medicine, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
| | - Mahmood Khan
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
- Department of Emergency Medicine, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Andrew R. Kohut
- Penn Heart and Vascular Center, University of Pennsylvania, Philadelphia, PA, USA
| | - Walter J. Koch
- Center for Translational Medicine, Department of Pharmacology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Harpreet Singh
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, USA
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
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Nepomuceno DB, D'Ávila Pessoa GC, Koerich LB, Pereira MH, Sant'Anna MRV, Araújo RN, Gontijo NF. cAMP: A second messenger involved in the mechanism of midgut alkalinization in Lutzomyia longipalpis. INSECT SCIENCE 2022; 29:1059-1070. [PMID: 34730278 DOI: 10.1111/1744-7917.12980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 09/06/2021] [Accepted: 10/19/2021] [Indexed: 06/13/2023]
Abstract
The sand fly Lutzomyia longipalpis is the main vector of Leishmania infantum in the Americas. Female sand flies ingest sugar-rich solutions and blood, which are digested in the midgut. Digestion of nutrients is an essential function performed by digestive enzymes, which require appropriate physiological conditions. One of the main aspects that influence enzymatic activity is the gut pH, which must be tightly controlled. Considering second messengers are frequently involved in the coordination of tightly regulated physiological events, we investigated if the second messenger cAMP would participate in the process of alkalinization in the abdominal midgut of female L. longipalpis. In midguts containing the indicator dye bromothymol-blue, cAMP stimulated the alkalinization of the midgut lumen. Through another technique based on the use of fluorescein as a pH indicator, we propose that cAMP is involved in the alkalinization of the midgut by activating HCO3- transport from the enterocyte's cytoplasm to the lumen. The results strongly suggested that the carrier responsible for this process would be a HCO3- /Cl- antiporter located in the enterocytes' apical membrane. Hematophagy promotes the release of alkalinizing hormones in the hemolymph; however, when the enzyme adenylyl cyclase, responsible for cAMP production, was inhibited, we observed that the hemolymph from blood-fed L. longipalpis' females did not stimulate midgut alkalinization. This result indicated that hormone-stimulated alkalinization is mediated by cAMP. In the present study, we provide evidences that cAMP has a key role in the control of intestinal pH.
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Affiliation(s)
- Denise Barguil Nepomuceno
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia/ICB, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Grasielle Caldas D'Ávila Pessoa
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia/ICB, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Leonardo Barbosa Koerich
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia/ICB, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Marcos Horácio Pereira
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia/ICB, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Mauricio Roberto Viana Sant'Anna
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia/ICB, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Ricardo Nascimento Araújo
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia/ICB, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Nelder Figueiredo Gontijo
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia/ICB, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
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Barguil Nepomuceno D, DÁvila Pessoa GC, Nascimento Araújo R, Barbosa Koerich L, Viana Sant’Anna MR, Horácio Pereira M, Figueiredo Gontijo N. Na+/K+-ATPase Activation by cAMP in the Midgut of Lutzomyia longipalpis (Lutz & Neiva, 1912; Diptera: Psychodidae). JOURNAL OF INSECT SCIENCE (ONLINE) 2022; 22:1. [PMID: 35271719 PMCID: PMC8912928 DOI: 10.1093/jisesa/ieac008] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Indexed: 06/14/2023]
Abstract
Lutzomyia longipalpis (Lutz & Neiva, 1912) females have been intensively studied regarding the regulation of midgut pH. The mechanisms involved in pH regulation are complex, and some aspects remain to be clarified. Here, we investigated the role of the Na+/K+-ATPase pump as an electrochemical potential generator and its modulation by the second messenger cAMP in the midgut of female L. longipalpis. Our results suggest that not only may Na+/K+-ATPase be the main generator of an electrochemical potential across membranes in the midgut of female L. longipalpis, but also its activity is positively regulated by cAMP. cAMP-mediated Na+/K+-ATPase pump activity might be necessary to maintain the transport of the nutrients produced during blood digestion.
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Affiliation(s)
- Denise Barguil Nepomuceno
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia—ICB, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, MG, Brazil
| | - Grasielle Caldas DÁvila Pessoa
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia—ICB, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, MG, Brazil
| | - Ricardo Nascimento Araújo
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia—ICB, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, MG, Brazil
| | - Leonardo Barbosa Koerich
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia—ICB, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, MG, Brazil
| | - Maurício Roberto Viana Sant’Anna
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia—ICB, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, MG, Brazil
| | - Marcos Horácio Pereira
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia—ICB, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, MG, Brazil
| | - Nelder Figueiredo Gontijo
- Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia—ICB, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, MG, Brazil
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Development of Specific Inhibitors for Oncogenic Phosphatase PPM1D by Using Ion-Responsive DNA Aptamer Library. Catalysts 2020. [DOI: 10.3390/catal10101153] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
(1) Background: Ser/Thr protein phosphatase PPM1D is an oncogenic protein. In normal cells, however, PPM1D plays essential roles in spermatogenesis and immune response. Hence, it is necessary to develop novel PPM1D inhibitors without side effects on normal cells. Stimuli-responsive molecules are suitable for the spatiotemporal regulation of inhibitory activity. (2) Methods: In this study, we designed an ion-responsive DNA aptamer library based on G-quadruplex DNA that can change its conformation and function in response to monovalent cations. (3) Results: Using this library, we identified the PPM1D specific inhibitor M1D-Q5F aptamer. The M1D-Q5F aptamer showed anti-cancer activity against breast cancer MCF7 cells. Interestingly, the induction of the structural change resulting in the formation of G-quadruplex upon stimulation by monovalent cations led to the enhancement of the inhibitory activity and binding affinity of M1D-Q5F. (4) Conclusions: These data suggest that the M1D-Q5F aptamer may act as a novel stimuli-responsive anti-cancer agent.
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Schwiebert EM, Benos DJ, Egan ME, Stutts MJ, Guggino WB. CFTR is a conductance regulator as well as a chloride channel. Physiol Rev 1999; 79:S145-66. [PMID: 9922379 DOI: 10.1152/physrev.1999.79.1.s145] [Citation(s) in RCA: 334] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
CFTR Is a Conductance Regulator as well as a Chloride Channel. Physiol. Rev. 79, Suppl.: S145-S166, 1999. - Cystic fibrosis transmembrane conductance regulator (CFTR) is a member of the ATP-binding cassette (ABC) transporter gene family. Although CFTR has the structure of a transporter that transports substrates across the membrane in a nonconductive manner, CFTR also has the intrinsic ability to conduct Cl- at much higher rates, a function unique to CFTR among this family of ABC transporters. Because Cl- transport was shown to be lost in cystic fibrosis (CF) epithelia long before the cloning of the CF gene and CFTR, CFTR Cl- channel function was considered to be paramount. Another equally valid perspective of CFTR, however, derives from its membership in a family of transporters that transports a multitude of different substances from chemotherapeutic drugs, to amino acids, to glutathione conjugates, to small peptides in a nonconductive manner. Moreover, at least two members of this ABC transporter family (mdr-1, SUR) can regulate other ion channels in the membrane. More simply, ABC transporters can regulate somehow the function of other cellular proteins or cellular functions. This review focuses on a plethora of studies showing that CFTR also regulates other ion channel proteins. It is the hope of the authors that the reader will take with him or her the message that CFTR is a conductance regulator as well as a Cl- channel.
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Affiliation(s)
- E M Schwiebert
- Department of Physiology and Biophysics, Gregory Fleming James CF Research Center, University of Alabama at Birmingham, Birmingham, Alabama, USA
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Grant AO. Mechanisms of action of antiarrhythmic drugs: from ion channel blockage to arrhythmia termination. Pacing Clin Electrophysiol 1997; 20:432-44. [PMID: 9058847 DOI: 10.1111/j.1540-8159.1997.tb06202.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Over the past decade, the strategies for arrhythmia management have been in transition. Physical methods to treat arrhythmias, such as ICDs and RF ablation, have undergone considerable refinement and wider application. Ischemic heart disease and congestive heart failure have been identified as clinical situations in which antiarrhythmic drugs have a significant proarrhythmic potential. However, drugs retain an important role in arrhythmia management. Strategies to mitigate the structural and functional changes that occur in hypertrophy, ischemia, and infarction have not been thoroughly explored. Membrane ion channels and receptors are the targets for the action of currently available drugs. The cloning and sequencing of these ion channels and receptors should improve the efficacy and specificity of drug design. Cardiac Na+, Ca2+, K+, and nonspecific cation channels have a clearly defined role in the generation of the normal action potential. Their specific roles in the various clinical arrhythmias is less certain. There are sufficient data to associate specific ionic channels with normal and abnormal automaticity and with reentry occurring in specific regions of the heart. A rational choice of antiarrthymic drugs can be made when an arrhythmogenic mechanism and the putative underlying membrane currents can be identified based on the clinical characteristics of the arrhythmia. For a majority of clinical arrhythmias, this ideal has not been achieved. When a particular drug is used to treat an arrhythmia, the full complement of its actions will depend on which multiple ion channels or receptors are blocked and the kinetics of drug interaction with these sites.
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Affiliation(s)
- A O Grant
- Department of Medicine, Duke University, Durham, North Carolina, USA.
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Asahina A, Moro O, Hosoi J, Lerner EA, Xu S, Takashima A, Granstein RD. Specific induction of cAMP in Langerhans cells by calcitonin gene-related peptide: relevance to functional effects. Proc Natl Acad Sci U S A 1995; 92:8323-7. [PMID: 7667288 PMCID: PMC41149 DOI: 10.1073/pnas.92.18.8323] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Epidermal Langerhans cells (LC) are associated anatomically with epidermal nerves, and a product of these nerves, calcitonin gene-related peptide (CGRP), inhibits the antigen-presenting capacity of LC and macrophages. As the CGRP receptor appears to be coupled to Gs alpha protein, which in turn activates adenylate cyclase, the ability of CGRP to induce cAMP in LC was examined and correlated with functional effects. LC were isolated from murine epidermal cells using antibodies on magnetic microspheres. Exposure to CGRP induced a significant increase in cAMP content, which could be inhibited by coculture with a truncated form of CGRP [CGRP-(8-37)] that is a specific competitive inhibitor of CGRP. Substance P and calcitonin failed to induce cAMP in LC. Although culture in CGRP reduced the ability of murine epidermal cells enriched for LC content to present pigeon cytochrome c to a responsive clone or to present antigen for elicitation of delayed-type hypersensitivity in immune mice, culture in forskolin had little or no effect on antigen presentation despite increased cAMP content of LC as much or more than that induced by CGRP. The effect of CGRP on antigen presentation in these systems could be blocked with CGRP-(8-37). CGRP inhibited the induction of B7-2 by lipopolysaccharide on peritoneal macrophages and a LC line, whereas calcitonin did not. CGRP induces specific accumulation of cAMP in LC and inhibits LC antigen-presenting function by a receptor-mediated event. However, the induction of cAMP by itself does not account for inhibition of antigen presentation. Suppression of the expression of B7-2 may be one mechanism by which CGRP inhibits antigen presentation.
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Affiliation(s)
- A Asahina
- MGH/Harvard Cutaneous Biology Research Center, Massachusetts General Hospital, Boston 02114, USA
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Philipson LH, Kuznetsov A, Toth PT, Murphy JF, Szabo G, Ma GH, Miller RJ. Functional expression of an epitope-tagged G protein-coupled K+ channel (GIRK1). J Biol Chem 1995; 270:14604-10. [PMID: 7540174 DOI: 10.1074/jbc.270.24.14604] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
An epitope-tagged form of an inwardly rectifying and G protein-coupled K+ channel (GIRK1-cp) was expressed at high levels in transfected mammalian cells. Immunoblot analysis of transfected human embryonic kidney cells (HEK293) and mouse insulinoma cells (beta TC3) revealed several GIRK1-cp polypeptides, including the major 59-kDa band, corresponding to the predicted mass of the GIRK1 polypeptide plus the epitope tag. Immunohistochemical staining using two anti-tag antibodies showed abundant immunoreactive material, which was predominantly concentrated in the perinuclear area in both transfected cell types. While functional GIRK1-cp message was present in poly(A)+ RNA prepared from HEK293 cells expressing GIRK1-cp protein, appropriate K+ currents could not be detected. In contrast, whole cell recordings made directly from transfected beta TC3 cells expressing GIRK1-cp revealed inwardly rectifying, pertussis toxin-sensitive currents activated by norepinephrine and galanin. Single channel recordings in excised patches of beta TC3 cells expressing GIRK1-cp showed rectifying K+ currents when activated by 50 microM guanosine 5'-O-(thiotriphosphate), with a slope conductance of 39.1 +/- 1.0 picosiemens. This is the first report of stable heterologous expression of a functional G protein-coupled K+ channel in mammalian cells. The activity of an epitope-tagged channel in insulinoma cells demonstrates the utility of this system for further biochemical and biophysical analyses of G protein-K+ channel interactions.
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Affiliation(s)
- L H Philipson
- Department of Medicine, University of Chicago, Illinois 60637, USA
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Hopp L, Bunker CH, Day BW. Quinine sensitive changes in cellular Na+ and K+ homeostasis of COS-7 cells caused by a lipophilic phenol red impurity. In Vitro Cell Dev Biol Anim 1995; 31:352-60. [PMID: 7543341 DOI: 10.1007/bf02634284] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
An impurity of phenol red (PRI) has been shown to markedly alter the intracellular Na+ and K+ homeostasis of several cell types. The effect of PRI seems to involve intracellular Ca(++)-dependent mechanisms. Using COS-7 cells as a model, we further characterized the mechanism of action of PRI by measuring cellular Na+/K+ contents and 86Rb+ efflux. Similar to human skin fibroblasts, in COS-7 cells calmodulin inhibition moderated the cationic transport effects of PRI. A TMB-8 dependent intracellular Ca++ pool does not seem to be involved in these transport events. We found no evidence for participation of the transcriptional-translational machinery in the effect of PRI. Both quinine and quinidine are able to prevent nearly all changes caused by PRI in the cellular Na+/K+ contents and 86Rb+ efflux. Although phenol red contained multiple impurities by high performance liquid chromatography (HPLC), phenolphthalein, a structurally close relative of phenol red, was free of any detectable contamination. Phenolphthalein elicited qualitatively similar transport changes to those observed during exposure to PRI. Regardless of the exact mechanism of action, we propose that the as yet unidentified substance is not a cellular toxin, rather it is a cationic transport modulator. Directly or indirectly, it may interact with the cellular Ca++/calmodulin system and activate some quinine/quinidine sensitive transport processes. This transport process is likely to be a Ca(++)-sensitive K+ channel but, due to the lack of specificity of quinine and quinidine, other transport mechanisms must be also considered. The chemical nature of PRI may be similar to phenolphthalein.
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Affiliation(s)
- L Hopp
- University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Department of Pediatrics, Newark 07103, USA
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Prattis SM, Horton SB, van Camp SD, Kornegay JN. Immunohistochemical detection of neural cell adhesion molecule and laminin in X-linked dystrophic dogs and mdx mice. J Comp Pathol 1994; 110:253-66. [PMID: 8040390 DOI: 10.1016/s0021-9975(08)80278-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Although dystrophin deficiency is known to be the genetic and biochemical defect causing Duchenne muscular dystrophy (DMD), much remains unknown about the underlying factors affecting clinical and pathological expression of the disease. Two animal forms of muscular dystrophy resembling DMD have been described. Neural cell adhesion molecule (NCAM) and laminin expression were examined in the proliferation-competent mdx mouse and non-regenerative "golden retriever muscular dystrophy dog" (GRMD). The results showed that (1) NCAM expression was greater in dystrophic dogs and mice than in age-matched normal animals, (2) myoblast-specific NCAM was greater in mdx mice than in dystrophic dogs, and (3) laminin strongly labelled mdx and GRMD myofibre membranes but was also sometimes found in individual interstitial cells of mdx muscle. Expression of these proteins may partly determine the clinicopathological expression of dystrophin deficiency.
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Affiliation(s)
- S M Prattis
- College of Veterinary Medicine, North Carolina State University, Raleigh 27606
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