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Luo M, Liu Y, Nikolovska K, Riederer B, Patrucco E, Hofmann F, Seidler U. cGMP-dependent kinase 2, Na +/H + exchanger NHE3, and PDZ-adaptor NHERF2 co-assemble in apical membrane microdomains. Acta Physiol (Oxf) 2024; 240:e14125. [PMID: 38533975 DOI: 10.1111/apha.14125] [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: 10/12/2023] [Revised: 01/30/2024] [Accepted: 02/14/2024] [Indexed: 03/28/2024]
Abstract
AIM Trafficking, membrane retention, and signal-specific regulation of the Na+/H+ exchanger 3 (NHE3) are modulated by the Na+/H+ Exchanger Regulatory Factor (NHERF) family of PDZ-adapter proteins. This study explored the assembly of NHE3 and NHERF2 with the cGMP-dependent kinase II (cGKII) within detergent-resistant membrane microdomains (DRMs, "lipid rafts") during in vivo guanylate cycle C receptor (Gucy2c) activation in murine small intestine. METHODS Small intestinal brush border membranes (siBBMs) were isolated from wild type, NHE3-deficient, cGMP-kinase II-deficient, and NHERF2-deficient mice, after oral application of the heat-stable Escherichia coli toxin (STa) analog linaclotide. Lipid raft and non-raft fractions were separated by Optiprep density gradient centrifugation of Triton X-solubilized siBBMs. Confocal microscopy was performed to study NHE3 redistribution after linaclotide application in vivo. RESULTS In the WT siBBM, NHE3, NHERF2, and cGKII were strongly raft associated. The raft association of NHE3, but not of cGKII, was NHERF2 dependent. After linaclotide application to WT mice, lipid raft association of NHE3 decreased, that of cGKII increased, while that of NHERF2 did not change. NHE3 expression in the BBM shifted from a microvillar to a terminal web region. The linaclotide-induced decrease in NHE3 raft association and in microvillar abundance was abolished in cGKII-deficient mice, and strongly reduced in NHERF2-deficient mice. CONCLUSION NHE3, cGKII, and NHERF2 form a lipid raft-associated signal complex in the siBBM, which mediates the inhibition of salt and water absorption by Gucy2c activation. NHERF2 enhances the raft association of NHE3, which is essential for its close interaction with the exclusively raft-associated activated cGKII.
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Affiliation(s)
- Min Luo
- Department of Gastroenterology, Hepatology, Infectiology and Endocrinology, Hannover Medical School, Hannover, Germany
- Department of Infectious Diseases, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yongjian Liu
- Department of Gastroenterology, Hepatology, Infectiology and Endocrinology, Hannover Medical School, Hannover, Germany
- Department of Endocrinology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Katerina Nikolovska
- Department of Gastroenterology, Hepatology, Infectiology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Brigitte Riederer
- Department of Gastroenterology, Hepatology, Infectiology and Endocrinology, Hannover Medical School, Hannover, Germany
| | - Enrico Patrucco
- Institut für Pharmakologie und Toxikologie, TU München, München, Germany
- Department of Molecular Biotechnology and Health Science, University of Torino, Torino, Italy
| | - Franz Hofmann
- Institut für Pharmakologie und Toxikologie, TU München, München, Germany
| | - Ursula Seidler
- Department of Gastroenterology, Hepatology, Infectiology and Endocrinology, Hannover Medical School, Hannover, Germany
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Salari A, Xiu R, Amiri M, Pallenberg ST, Schreiber R, Dittrich AM, Tümmler B, Kunzelmann K, Seidler U. The Anion Channel TMEM16a/Ano1 Modulates CFTR Activity, but Does Not Function as an Apical Anion Channel in Colonic Epithelium from Cystic Fibrosis Patients and Healthy Individuals. Int J Mol Sci 2023; 24:14214. [PMID: 37762516 PMCID: PMC10531629 DOI: 10.3390/ijms241814214] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 09/08/2023] [Accepted: 09/11/2023] [Indexed: 09/29/2023] Open
Abstract
Studies in human colonic cell lines and murine intestine suggest the presence of a Ca2+-activated anion channel, presumably TMEM16a. Is there a potential for fluid secretion in patients with severe cystic fibrosis transmembrane conductance regulator (CFTR) mutations by activating this alternative pathway? Two-dimensional nondifferentiated colonoid-myofibroblast cocultures resembling transit amplifying/progenitor (TA/PE) cells, as well as differentiated monolayer (DM) cultures resembling near-surface cells, were established from both healthy controls (HLs) and patients with severe functional defects in the CFTR gene (PwCF). F508del mutant and CFTR knockout (null) mice ileal and colonic mucosa was also studied. HL TA/PE monolayers displayed a robust short-circuit current response (ΔIeq) to UTP (100 µM), forskolin (Fsk, 10 µM) and carbachol (CCH, 100 µM), while ΔIeq was much smaller in differentiated monolayers. The selective TMEM16a inhibitor Ani9 (up to 30 µM) did not alter the response to luminal UTP, significantly decreased Fsk-induced ΔIeq, and significantly increased CCH-induced ΔIeq in HL TA/PE colonoid monolayers. The PwCF TA/PE and the PwCF differentiated monolayers displayed negligible agonist-induced ΔIeq, without a significant effect of Ani9. When TMEM16a was localized in intracellular structures, a staining in the apical membrane was not detected. TMEM16a is highly expressed in human colonoid monolayers resembling transit amplifying cells of the colonic cryptal neck zone, from both HL and PwCF. While it may play a role in modulating agonist-induced CFTR-mediated anion currents, it is not localized in the apical membrane, and it has no function as an apical anion channel in cystic fibrosis (CF) and healthy human colonic epithelium.
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Affiliation(s)
- Azam Salari
- Department of Gastroenterology, Hannover Medical School, 30625 Hannover, Germany; (A.S.); (R.X.); (M.A.)
| | - Renjie Xiu
- Department of Gastroenterology, Hannover Medical School, 30625 Hannover, Germany; (A.S.); (R.X.); (M.A.)
| | - Mahdi Amiri
- Department of Gastroenterology, Hannover Medical School, 30625 Hannover, Germany; (A.S.); (R.X.); (M.A.)
| | - Sophia Theres Pallenberg
- Department of Pediatric Pneumonology, Allergology and Neonatology, Hannover Medical School, 30625 Hannover, Germany (A.-M.D.)
| | - Rainer Schreiber
- Institute of Physiology, University of Regensburg, 93040 Regensburg, Germany; (R.S.); (K.K.)
| | - Anna-Maria Dittrich
- Department of Pediatric Pneumonology, Allergology and Neonatology, Hannover Medical School, 30625 Hannover, Germany (A.-M.D.)
| | - Burkhard Tümmler
- Department of Pediatric Pneumonology, Allergology and Neonatology, Hannover Medical School, 30625 Hannover, Germany (A.-M.D.)
| | - Karl Kunzelmann
- Institute of Physiology, University of Regensburg, 93040 Regensburg, Germany; (R.S.); (K.K.)
| | - Ursula Seidler
- Department of Gastroenterology, Hannover Medical School, 30625 Hannover, Germany; (A.S.); (R.X.); (M.A.)
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Fan W, Tan Q. Application of the steady-state intestinal perfusion system in measuring intestinal fluid absorption and bicarbonate secretion in vivo. Front Physiol 2023; 14:1163888. [PMID: 37497438 PMCID: PMC10366686 DOI: 10.3389/fphys.2023.1163888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 06/26/2023] [Indexed: 07/28/2023] Open
Abstract
Background: The steady-state intestinal perfusion system represents a tool used in measuring intestinal fluid absorption and bicarbonate secretion in vivo; however, detailed procedures and parameters were not elucidated fully. Aim: We focused on the methods of the steady-state intestinal perfusion system comprehensively including the blood pressure, hematocrit, blood gas, and heart rate of mouse. Methods: Anesthetized, tracheally intubated, and artificially ventilated mice were used for this system. The blood pressure, hematocrit, blood gas, heart rate, and rate of fluid absorption and HCO3 - secretion of the small intestine and colon at different time points were evaluated. Results: Blood pressure, hematocrit, blood gas, and heart rate became stable at the 30 min time point after completion of surgery and could be maintained for 2 h. Rates of fluid absorption and bicarbonate secretion were also kept stable during the period of steady state of mice. Rates of fluid absorption and bicarbonate secretion were different among the jejunum, ileum, proximal, and mid-distal colon. Conclusion: The steady-state intestinal perfusion system is a reliable system for measuring intestinal fluid absorption and bicarbonate secretion in vivo.
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Barton JR, Londregan AK, Alexander TD, Entezari AA, Bar-Ad S, Cheng L, Lepore AC, Snook AE, Covarrubias M, Waldman SA. Intestinal neuropod cell GUCY2C regulates visceral pain. J Clin Invest 2023; 133:e165578. [PMID: 36548082 PMCID: PMC9927949 DOI: 10.1172/jci165578] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022] Open
Abstract
Visceral pain (VP) is a global problem with complex etiologies and limited therapeutic options. Guanylyl cyclase C (GUCY2C), an intestinal receptor producing cyclic GMP(cGMP), which regulates luminal fluid secretion, has emerged as a therapeutic target for VP. Indeed, FDA-approved GUCY2C agonists ameliorate VP in patients with chronic constipation syndromes, although analgesic mechanisms remain obscure. Here, we revealed that intestinal GUCY2C was selectively enriched in neuropod cells, a type of enteroendocrine cell that synapses with submucosal neurons in mice and humans. GUCY2Chi neuropod cells associated with cocultured dorsal root ganglia neurons and induced hyperexcitability, reducing the rheobase and increasing the resulting number of evoked action potentials. Conversely, the GUCY2C agonist linaclotide eliminated neuronal hyperexcitability produced by GUCY2C-sufficient - but not GUCY2C-deficient - neuropod cells, an effect independent of bulk epithelial cells or extracellular cGMP. Genetic elimination of intestinal GUCY2C amplified nociceptive signaling in VP that was comparable with chemically induced VP but refractory to linaclotide. Importantly, eliminating GUCY2C selectively in neuropod cells also increased nociceptive signaling and VP that was refractory to linaclotide. In the context of loss of GUCY2C hormones in patients with VP, these observations suggest a specific role for neuropod GUCY2C signaling in the pathophysiology and treatment of these pain syndromes.
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Affiliation(s)
| | | | | | | | - Shely Bar-Ad
- Department of Pharmacology, Physiology, & Cancer Biology
| | | | | | - Adam E. Snook
- Department of Pharmacology, Physiology, & Cancer Biology
- Department of Microbiology & Immunology, and
- Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | | | - Scott A. Waldman
- Department of Pharmacology, Physiology, & Cancer Biology
- Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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Nikolovska K, Seidler UE, Stock C. The Role of Plasma Membrane Sodium/Hydrogen Exchangers in Gastrointestinal Functions: Proliferation and Differentiation, Fluid/Electrolyte Transport and Barrier Integrity. Front Physiol 2022; 13:899286. [PMID: 35665228 PMCID: PMC9159811 DOI: 10.3389/fphys.2022.899286] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 04/19/2022] [Indexed: 12/11/2022] Open
Abstract
The five plasma membrane Na+/H+ exchanger (NHE) isoforms in the gastrointestinal tract are characterized by distinct cellular localization, tissue distribution, inhibitor sensitivities, and physiological regulation. NHE1 (Slc9a1) is ubiquitously expressed along the gastrointestinal tract in the basolateral membrane of enterocytes, but so far, an exclusive role for NHE1 in enterocyte physiology has remained elusive. NHE2 (Slc9a2) and NHE8 (Slc9a8) are apically expressed isoforms with ubiquitous distribution along the colonic crypt axis. They are involved in pHi regulation of intestinal epithelial cells. Combined use of a knockout mouse model, intestinal organoid technology, and specific inhibitors revealed previously unrecognized actions of NHE2 and NHE8 in enterocyte proliferation and differentiation. NHE3 (Slc9a3), expressed in the apical membrane of differentiated intestinal epithelial cells, functions as the predominant nutrient-independent Na+ absorptive mechanism in the gut. The new selective NHE3 inhibitor (Tenapanor) allowed discovery of novel pathophysiological and drug-targetable NHE3 functions in cystic-fibrosis associated intestinal obstructions. NHE4, expressed in the basolateral membrane of parietal cells, is essential for parietal cell integrity and acid secretory function, through its role in cell volume regulation. This review focuses on the expression, regulation and activity of the five plasma membrane Na+/H+ exchangers in the gastrointestinal tract, emphasizing their role in maintaining intestinal homeostasis, or their impact on disease pathogenesis. We point to major open questions in identifying NHE interacting partners in central cellular pathways and processes and the necessity of determining their physiological role in a system where their endogenous expression/activity is maintained, such as organoids derived from different parts of the gastrointestinal tract.
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Mechanisms of Action of Current Pharmacologic Options for the Treatment of Chronic Idiopathic Constipation and Irritable Bowel Syndrome With Constipation. Am J Gastroenterol 2022; 117:S6-S13. [PMID: 35354770 DOI: 10.14309/ajg.0000000000001687] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 01/31/2022] [Indexed: 12/11/2022]
Abstract
Multiple therapeutic agents are currently available for the treatment of chronic idiopathic constipation and irritable bowel syndrome with constipation. A better understanding of the mechanism of action of each treatment provides important insights into expected responses and is key to optimizing treatment outcomes. Some constipation treatments, such as stimulant laxatives, may increase bowel movement frequency but are ineffective at relieving, and may even exacerbate, abdominal symptoms. On the contrary, prescription treatments, such as the guanylyl cyclase-C agonists, for example, may improve bowel symptoms and reduce visceral hypersensitivity. This review summarizes the mechanisms of action of commonly used over-the-counter and prescription therapies for chronic idiopathic constipation and irritable bowel syndrome with constipation, outlining how these mechanisms contribute to the efficacy and safety of each treatment option.
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Stephens CE, Whittamore JM, Hatch M. The role of NHE3 (Slc9a3) in oxalate and sodium transport by mouse intestine and regulation by cAMP. Physiol Rep 2021; 9:e14828. [PMID: 33904662 PMCID: PMC8077127 DOI: 10.14814/phy2.14828] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 03/01/2021] [Accepted: 03/09/2021] [Indexed: 12/14/2022] Open
Abstract
Intestinal oxalate transport involves Cl−/HCO3− exchangers but how this transport is regulated is not currently known. NHE3 (Slc9a3), an apical Na+/H+ exchanger, is an established target for regulation of electroneutral NaCl absorption working in concert with Cl−/HCO3− exchangers. To test whether NHE3 could be involved in regulation of intestinal oxalate transport and renal oxalate handling we compared urinary oxalate excretion rates and intestinal transepithelial fluxes of 14C‐oxalate and 22Na+ between NHE3 KO and wild‐type (WT) mice. NHE3 KO kidneys had lower creatinine clearance suggesting reduced GFR, but urinary oxalate excretion rates (µmol/24 h) were similar compared to the WT but doubled when expressed as a ratio of creatinine. Intestinal transepithelial fluxes of 14C‐oxalate and 22Na+ were measured in the distal ileum, cecum, and distal colon. The absence of NHE3 did not affect basal net transport rates of oxalate or sodium across any intestinal section examined. Stimulation of intracellular cAMP with forskolin (FSK) and 3‐isobutyl‐1‐methylxanthine (IBMX) led to an increase in net oxalate secretion in the WT distal ileum and cecum and inhibition of sodium absorption in the cecum and distal colon. In NHE3 KO cecum, cAMP stimulation of oxalate secretion was impaired suggesting the possibility of a role for NHE3 in this process. Although, there is little evidence for a role of NHE3 in basal intestinal oxalate fluxes, NHE3 may be important for cAMP stimulation of oxalate in the cecum and for renal handling of oxalate.
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Affiliation(s)
- Christine E Stephens
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Jonathan M Whittamore
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Marguerite Hatch
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
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Tan Q, di Stefano G, Tan X, Renjie X, Römermann D, Talbot SR, Seidler UE. Inhibition of Na + /H + exchanger isoform 3 improves gut fluidity and alkalinity in cystic fibrosis transmembrane conductance regulator-deficient and F508del mutant mice. Br J Pharmacol 2021; 178:1018-1036. [PMID: 33179259 DOI: 10.1111/bph.15323] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 11/01/2020] [Accepted: 11/02/2020] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND AND PURPOSE Constipation and intestinal obstructive episodes are major health problems in cystic fibrosis (CF) patients. Three FDA-approved drugs against constipation-prone irritable bowel syndrome were tested for their ability to increase luminal fluidity and alkalinity in cystic fibrosis transmembrane conductance regulator (CFTR) null (cftr-/- ) and F508del mutant (F508delmut/mut ) murine intestine. EXPERIMENTAL APPROACH Guanylate cyclase C agonist linaclotide, PGE1 analogue lubiprostone and intestine-specific NHE3 inhibitor tenapanor were perfused through a ~3 cm jejunal, proximal or mid-distal colonic segment in anaesthetized cftr-/- , F508delmut/mut and WT mice. Net fluid balance was determined gravimetrically and alkaline output by pH-stat back titration. KEY RESULTS Basal jejunal fluid absorptive rates were significantly higher and basal HCO3 - output was significantly lower in cftr-/- and F508delmut/mut compared to WT mice. In cftr-/- and F508delmut/mut mice, all three drugs significantly inhibited the fluid absorptive rate and increased alkaline output in the jejunum and tenapanor and lubiprostone, but not linaclotide, in the colon. After tenapanor pre-incubation, linaclotide elicited a robust fluid secretory response in WT jejunum, while no further change in absorptive rates was observed in cftr-/- and F508delmut/mut jejunum, suggesting that the increase in gut fluidity and alkalinity by linaclotide in CF gut is mediated via NHE3 inhibition. Lubiprostone also inhibited fluid absorption in cftr-/- and F508delmut/mut jejunum via NHE3 inhibition but had a residual NHE3-independent effect. CONCLUSION AND IMPLICATIONS Linaclotide, lubiprostone and tenapanor reduced fluid absorption and increased alkaline output in the CF gut. Their application may ameliorate constipation and reduce obstructive episodes in CF patients.
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Affiliation(s)
- Qinghai Tan
- Department of Gastroenterology, Hannover Medical School, Hanover, Germany
| | | | - Xinjie Tan
- Department of Gastroenterology, Hannover Medical School, Hanover, Germany
| | - Xiu Renjie
- Department of Gastroenterology, Hannover Medical School, Hanover, Germany
| | - Dorothee Römermann
- Department of Gastroenterology, Hannover Medical School, Hanover, Germany
| | - Steven R Talbot
- Institute of Veterinary Research, Hannover Medical School, Hanover, Germany
| | - Ursula E Seidler
- Department of Gastroenterology, Hannover Medical School, Hanover, Germany
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Flickinger JC, Rappaport JA, Barton JR, Baybutt TR, Pattison AM, Snook AE, Waldman SA. Guanylyl cyclase C as a biomarker for immunotherapies for the treatment of gastrointestinal malignancies. Biomark Med 2021; 15:201-217. [PMID: 33470843 PMCID: PMC8293028 DOI: 10.2217/bmm-2020-0359] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 12/18/2020] [Indexed: 12/12/2022] Open
Abstract
Gastrointestinal cancers encompass a diverse class of tumors arising in the GI tract, including esophagus, stomach, pancreas and colorectum. Collectively, gastrointestinal cancers compose a high fraction of all cancer deaths, highlighting an unmet need for novel and effective therapies. In this context, the transmembrane receptor guanylyl cyclase C (GUCY2C) has emerged as an attractive target for the prevention, detection and treatment of many gastrointestinal tumors. GUCY2C is an intestinally-restricted protein implicated in tumorigenesis that is universally expressed by primary and metastatic colorectal tumors as well as ectopically expressed by esophageal, gastric and pancreatic cancers. This review summarizes the current state of GUCY2C-targeted modalities in the management of gastrointestinal malignancies, with special focus on colorectal cancer, the most incident gastrointestinal malignancy.
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Affiliation(s)
- John C Flickinger
- Department of Pharmacology & Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Jeffrey A Rappaport
- Department of Pharmacology & Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Joshua R Barton
- Department of Pharmacology & Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Trevor R Baybutt
- Department of Pharmacology & Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Amanda M Pattison
- Department of Pharmacology & Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Adam E Snook
- Department of Pharmacology & Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Scott A Waldman
- Department of Pharmacology & Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA 19107, USA
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de Jonge HR, Ardelean MC, Bijvelds MJC, Vergani P. Strategies for cystic fibrosis transmembrane conductance regulator inhibition: from molecular mechanisms to treatment for secretory diarrhoeas. FEBS Lett 2020; 594:4085-4108. [PMID: 33113586 PMCID: PMC7756540 DOI: 10.1002/1873-3468.13971] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 09/22/2020] [Accepted: 10/15/2020] [Indexed: 02/06/2023]
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) is an unusual ABC transporter. It acts as an anion‐selective channel that drives osmotic fluid transport across many epithelia. In the gut, CFTR is crucial for maintaining fluid and acid‐base homeostasis, and its activity is tightly controlled by multiple neuro‐endocrine factors. However, microbial toxins can disrupt this intricate control mechanism and trigger protracted activation of CFTR. This results in the massive faecal water loss, metabolic acidosis and dehydration that characterize secretory diarrhoeas, a major cause of malnutrition and death of children under 5 years of age. Compounds that inhibit CFTR could improve emergency treatment of diarrhoeal disease. Drawing on recent structural and functional insight, we discuss how existing CFTR inhibitors function at the molecular and cellular level. We compare their mechanisms of action to those of inhibitors of related ABC transporters, revealing some unexpected features of drug action on CFTR. Although challenges remain, especially relating to the practical effectiveness of currently available CFTR inhibitors, we discuss how recent technological advances might help develop therapies to better address this important global health need.
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Affiliation(s)
- Hugo R. de Jonge
- Department of Gastroenterology & HepatologyErasmus University Medical CenterRotterdamThe Netherlands
| | - Maria C. Ardelean
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonUK
- Department of Natural SciencesUniversity College LondonUK
| | - Marcel J. C. Bijvelds
- Department of Gastroenterology & HepatologyErasmus University Medical CenterRotterdamThe Netherlands
| | - Paola Vergani
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonUK
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