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Michaels WE, Pena-Rasgado C, Kotaria R, Bridges RJ, Hastings ML. Open reading frame correction using splice-switching antisense oligonucleotides for the treatment of cystic fibrosis. Proc Natl Acad Sci U S A 2022; 119:e2114886119. [PMID: 35017302 PMCID: PMC8784102 DOI: 10.1073/pnas.2114886119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 12/03/2021] [Indexed: 12/11/2022] Open
Abstract
CFTR gene mutations that result in the introduction of premature termination codons (PTCs) are common in cystic fibrosis (CF). This mutation type causes a severe form of the disease, likely because of low CFTR messenger RNA (mRNA) expression as a result of nonsense-mediated mRNA decay, as well as the production of a nonfunctional, truncated CFTR protein. Current therapeutics for CF, which target residual protein function, are less effective in patients with these types of mutations due in part to low CFTR protein levels. Splice-switching antisense oligonucleotides (ASOs), designed to induce skipping of exons in order to restore the mRNA open reading frame, have shown therapeutic promise preclinically and clinically for a number of diseases. We hypothesized that ASO-mediated skipping of CFTR exon 23 would recover CFTR activity associated with terminating mutations in the exon, including CFTR p.W1282X, the fifth most common mutation in CF. Here, we show that CFTR lacking the amino acids encoding exon 23 is partially functional and responsive to corrector and modulator drugs currently in clinical use. ASO-induced exon 23 skipping rescued CFTR expression and chloride current in primary human bronchial epithelial cells isolated from a homozygote CFTR-W1282X patient. These results support the use of ASOs in treating CF patients with CFTR class I mutations in exon 23 that result in unstable CFTR mRNA and truncations of the CFTR protein.
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Affiliation(s)
- Wren E Michaels
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064
- School of Graduate and Postdoctoral Studies, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064
| | - Cecilia Pena-Rasgado
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064
| | - Rusudan Kotaria
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064
| | - Robert J Bridges
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064;
| | - Michelle L Hastings
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064;
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2
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Conese M, Di Gioia S. Pathophysiology of Lung Disease and Wound Repair in Cystic Fibrosis. Pathophysiology 2021; 28:155-88. [PMID: 35366275 DOI: 10.3390/pathophysiology28010011] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 03/08/2021] [Accepted: 03/08/2021] [Indexed: 12/11/2022] Open
Abstract
Cystic fibrosis (CF) is an autosomal recessive, life-threatening condition affecting many organs and tissues, the lung disease being the chief cause of morbidity and mortality. Mutations affecting the CF Transmembrane Conductance Regulator (CFTR) gene determine the expression of a dysfunctional protein that, in turn, triggers a pathophysiological cascade, leading to airway epithelium injury and remodeling. In vitro and in vivo studies point to a dysregulated regeneration and wound repair in CF airways, to be traced back to epithelial CFTR lack/dysfunction. Subsequent altered ion/fluid fluxes and/or signaling result in reduced cell migration and proliferation. Furthermore, the epithelial-mesenchymal transition appears to be partially triggered in CF, contributing to wound closure alteration. Finally, we pose our attention to diverse approaches to tackle this defect, discussing the therapeutic role of protease inhibitors, CFTR modulators and mesenchymal stem cells. Although the pathophysiology of wound repair in CF has been disclosed in some mechanisms, further studies are warranted to understand the cellular and molecular events in more details and to better address therapeutic interventions.
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Abstract
The field of cAMP signaling is witnessing exciting developments with the recognition that cAMP is compartmentalized and that spatial regulation of cAMP is critical for faithful signal coding. This realization has changed our understanding of cAMP signaling from a model in which cAMP connects a receptor at the plasma membrane to an intracellular effector in a linear pathway to a model in which cAMP signals propagate within a complex network of alternative branches and the specific functional outcome strictly depends on local regulation of cAMP levels and on selective activation of a limited number of branches within the network. In this review, we cover some of the early studies and summarize more recent evidence supporting the model of compartmentalized cAMP signaling, and we discuss how this knowledge is starting to provide original mechanistic insight into cell physiology and a novel framework for the identification of disease mechanisms that potentially opens new avenues for therapeutic interventions.
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Affiliation(s)
- Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Anna Zerio
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Miguel J Lobo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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4
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Mancini G, Loberto N, Olioso D, Dechecchi MC, Cabrini G, Mauri L, Bassi R, Schiumarini D, Chiricozzi E, Lippi G, Pesce E, Sonnino S, Pedemonte N, Tamanini A, Aureli M. GM1 as Adjuvant of Innovative Therapies for Cystic Fibrosis Disease. Int J Mol Sci 2020; 21:E4486. [PMID: 32599772 DOI: 10.3390/ijms21124486] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 06/20/2020] [Accepted: 06/21/2020] [Indexed: 01/26/2023] Open
Abstract
Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein is expressed at the apical plasma membrane (PM) of different epithelial cells. The most common mutation responsible for the onset of cystic fibrosis (CF), F508del, inhibits the biosynthesis and transport of the protein at PM, and also presents gating and stability defects of the membrane anion channel upon its rescue by the use of correctors and potentiators. This prompted a multiple drug strategy for F508delCFTR aimed simultaneously at its rescue, functional potentiation and PM stabilization. Since ganglioside GM1 is involved in the functional stabilization of transmembrane proteins, we investigated its role as an adjuvant to increase the effectiveness of CFTR modulators. According to our results, we found that GM1 resides in the same PM microenvironment as CFTR. In CF cells, the expression of the mutated channel is accompanied by a decrease in the PM GM1 content. Interestingly, by the exogenous administration of GM1, it becomes a component of the PM, reducing the destabilizing effect of the potentiator VX-770 on rescued CFTR protein expression/function and improving its stabilization. This evidence could represent a starting point for developing innovative therapeutic strategies based on the co-administration of GM1, correctors and potentiators, with the aim of improving F508del CFTR function.
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5
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Strub MD, McCray, Jr. PB. Transcriptomic and Proteostasis Networks of CFTR and the Development of Small Molecule Modulators for the Treatment of Cystic Fibrosis Lung Disease. Genes (Basel) 2020; 11:genes11050546. [PMID: 32414011 PMCID: PMC7288469 DOI: 10.3390/genes11050546] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 05/07/2020] [Accepted: 05/08/2020] [Indexed: 12/18/2022] Open
Abstract
Cystic fibrosis (CF) is a lethal autosomal recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. The diversity of mutations and the multiple ways by which the protein is affected present challenges for therapeutic development. The observation that the Phe508del-CFTR mutant protein is temperature sensitive provided proof of principle that mutant CFTR could escape proteosomal degradation and retain partial function. Several specific protein interactors and quality control checkpoints encountered by CFTR during its proteostasis have been investigated for therapeutic purposes, but remain incompletely understood. Furthermore, pharmacological manipulation of many CFTR interactors has not been thoroughly investigated for the rescue of Phe508del-CFTR. However, high-throughput screening technologies helped identify several small molecule modulators that rescue CFTR from proteosomal degradation and restore partial function to the protein. Here, we discuss the current state of CFTR transcriptomic and biogenesis research and small molecule therapy development. We also review recent progress in CFTR proteostasis modulators and discuss how such treatments could complement current FDA-approved small molecules.
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Affiliation(s)
- Matthew D. Strub
- Interdisciplinary Graduate Program in Genetics, The University of Iowa, Iowa City, IA 52242, USA;
- Stead Family Department of Pediatrics, The University of Iowa, Iowa City, IA 52242, USA
| | - Paul B. McCray, Jr.
- Interdisciplinary Graduate Program in Genetics, The University of Iowa, Iowa City, IA 52242, USA;
- Stead Family Department of Pediatrics, The University of Iowa, Iowa City, IA 52242, USA
- Correspondence: ; Tel.: +1-(319)-335-6844
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6
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Martin ER, Barbieri A, Ford RC, Robinson RC. In vivo crystals reveal critical features of the interaction between cystic fibrosis transmembrane conductance regulator (CFTR) and the PDZ2 domain of Na +/H + exchange cofactor NHERF1. J Biol Chem 2020; 295:4464-4476. [PMID: 32014995 DOI: 10.1074/jbc.ra119.012015] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 01/17/2020] [Indexed: 12/23/2022] Open
Abstract
Crystallization of recombinant proteins has been fundamental to our understanding of protein function, dysfunction, and molecular recognition. However, this information has often been gleaned under extremely nonphysiological protein, salt, and H+ concentrations. Here, we describe the development of a robust Inka1-Box (iBox)-PAK4cat system that spontaneously crystallizes in several mammalian cell types. The semi-quantitative assay described here allows the measurement of in vivo protein-protein interactions using a novel GFP-linked reporter system that produces fluorescent readouts from protein crystals. We combined this assay with in vitro X-ray crystallography and molecular dynamics studies to characterize the molecular determinants of the interaction between the PDZ2 domain of Na+/H+ exchange regulatory cofactor NHE-RF1 (NHERF1) and cystic fibrosis transmembrane conductance regulator (CFTR), a protein complex pertinent to the genetic disease cystic fibrosis. These experiments revealed the crystal structure of the extended PDZ domain of NHERF1 and indicated, contrary to what has been previously reported, that residue selection at positions -1 and -3 of the PDZ-binding motif influences the affinity and specificity of the NHERF1 PDZ2-CFTR interaction. Our results suggest that this system could be utilized to screen additional protein-protein interactions, provided they can be accommodated within the spacious iBox-PAK4cat lattice.
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Affiliation(s)
- Eleanor R Martin
- School of Biological Sciences, Faculty of Biology Medicine and Health, Michael Smith Building, The University of Manchester, Manchester, M13 9PL, United Kingdom.,Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Biopolis 138673, Singapore
| | - Alessandro Barbieri
- School of Biological Sciences, Faculty of Biology Medicine and Health, Michael Smith Building, The University of Manchester, Manchester, M13 9PL, United Kingdom.,Bioinformatics Institute (BII), A*STAR (Agency for Science, Technology and Research), Biopolis 138671, Singapore
| | - Robert C Ford
- School of Biological Sciences, Faculty of Biology Medicine and Health, Michael Smith Building, The University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Robert C Robinson
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Biopolis 138673, Singapore .,School of Biomolecular Science and Engineering (BSE), Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong 21210, Thailand.,Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
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Abstract
Clostridiumdifficile (CD) is a common pathogen that causes severe gastrointestinal inflammatory diarrhea in patients undergoing antibiotic therapy. Its virulence derives from two toxins, toxin CD, A and B (TcdA and TcdB) (Borriello et al. Rev Infect Dis 12, Suppl 2: S185-191, 1990). Among the prime candidates for CD colonization are patients with cystic fibrosis (CF), who are routinely treated with antibiotics and frequently hospitalized. Indeed, ~50% of patients with CF are colonized with virulent forms of CD but do not exhibit diarrhea (Bauer et al. Clin Microbiol Infect 20: O446-O449, 2014; Binkovitz et al. Am J Roentgenol 172: 517-521, 199; Zemljic et al. Anaerobe 16: 527-532, 2010). We found that TcdB has global effects on colonic cells, including reducing the steady-state levels of sodium-proton exchange regulatory factors, reducing the levels of heat shock protein (Hsp) 27, and increasing the fraction of total Hsp27 bound to the cystic fibrosis transmembrane conductance regulator (CFTR). Also, since some mutations in CFTR seem to be protective, we asked whether CFTR is a target of TcdB. We show here that TcdB increases the maturation of CFTR and transiently increases its function. These combined effects promote increased surface expression of CFTR, resulting in a transient increase in Cl- secretion. This increase is followed by a precipitous decline in both CFTR-dependent Cl- secretion and transepithelial resistance (TER), suggesting a breakdown in the epithelial cells' tight junctions. We also found that overexpressing Hsp27 reverses some of the deleterious effects of TcdB, in particular preserving TER and therefore likely the maintenance of barrier function. Thus, our data suggest that Hsp27 plays a role in the diarrhea generated by CD infection and is a potential therapeutic target for treating this diarrhea.NEW & NOTEWORTHYClostridium difficile (CD) is a common pathogen that causes severe gastrointestinal inflammatory diarrhea in patients undergoing antibiotic therapy. We provide new evidence that heat shock protein (Hsp) 27 is one of the key players in CD pathology and that increasing Hsp27 can prevent the decrease in transepithelial resistance induced by toxin CD B, pointing the way for pharmacologic therapies for patients with chronic CD infection that can increase Hsp27 as a means to mitigate the effects of CD on gastrointestinal pathology.
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Affiliation(s)
- Murali K. Yanda
- Departments of Medicine and Physiology, Johns Hopkins University, Baltimore, Maryland
| | - William B. Guggino
- Departments of Medicine and Physiology, Johns Hopkins University, Baltimore, Maryland
| | - Liudmila Cebotaru
- Departments of Medicine and Physiology, Johns Hopkins University, Baltimore, Maryland
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8
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Abstract
Metabolic disorders are a group of interrelated conditions which increases the risk of developing heart diseases, stroke, and diabetes. These usually occur as a consequence of deficiency of enzymes involved in biochemical reactions in the body. The dietary habits, lack of physical exercise, stress, and genetic susceptibility leads to an increased risk of developing metabolic disorders. A diet rich in processed food items containing high calories aggravates the production of a purine metabolite, the uric acid (UA). UA functions as an antioxidant, protects against inflammation, aging, and cancer. It exists as urate ions in the circulation and blood level of UA is maintained by a balance between its production in the liver and its excretion by the renal tubules. The regular excretion of UA through the kidneys is necessary to maintain optimum blood levels of UA (3-7 mg/dl). There are various transporters of uric acid present around the renal tubules, which help in reabsorption of UA into the blood. These urate transporters (UT) are proteins coded in the genes. Mutations in these genes may prompt disturbances in UA reabsorption, and could lead to the development of hyperuricaemia, insulin resistance, endothelial dysfunction, diabetes and other metabolic diseases. This paper reviews eight such genes coding for UTs and attempts to unravel the link between the activities of UA, UTs, and the consequences during mutations in the genes coding for the UTs in the development of metabolic disorders. The genes reviewed included SLC2A9, SLC17A1, SLC22A12, SLC16A9, GCKR, LRRC16A, PDZK1, and ABCG2.
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9
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Sun H, Wang Y, Zhang J, Chen Y, Liu Y, Lin Z, Liu M, Sheng K, Liao H, Tsang KS, Zhang X, Jiang X, Xu W, Mao M, Chan HC. CFTR mutation enhances Dishevelled degradation and results in impairment of Wnt-dependent hematopoiesis. Cell Death Dis 2018; 9:275. [PMID: 29449653 DOI: 10.1038/s41419-018-0311-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 01/04/2018] [Accepted: 01/08/2018] [Indexed: 01/16/2023]
Abstract
Mutations of cystic fibrosis transmembrane conductance regulator (CFTR) cause cystic fibrosis (CF) with a multitude of clinical manifestations. Some CF patients develop clinically significant anemia, suggesting that CFTR may regulate hematopoiesis. Here, we report that cftr mutant zebrafish model exhibits primitive and definitive hematopoietic defects with impaired Wnt signaling. Cftr is found to interact, via its PDZ-binding domain (PDZBD), with Dishevelled (Dvl), a key component of Wnt signaling required for hematopoietic progenitor specification, thus protecting Dvl from Dapper1 (Dpr1)-induced lysosomal degradation. Defective hematopoiesis and impaired Wnt signaling in cftr mutant can be rescued by overexpression of wild-type or channel function-defective G551D mutant CFTR with an intact PDZBD, but not Cftr with mutations in the PDZBD. Analysis of human database (http://r2.amc.nl) shows that CFTR is positively correlated with DVL2 and Wnt-related hematopoietic factors in human blood system. The results reveal a previously unrecognized role of CFTR, which is independent of its channel function, in regulating DVL degradation and thus Wnt signaling required for hematopoiesis in both zebrafish and humans, providing an explanation for the anemic phenotype of CF patients.
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10
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Abstract
The vectorial secretion and absorption of fluid and solutes by epithelial cells is dependent on the polarized expression of membrane solute transporters and channels at the apical and basolateral membranes. The establishment and maintenance of this polarized expression of transporters and channels are affected by divers protein-trafficking complexes. Moreover, regulation of the magnitude of transport is often under control of physiological stimuli, again through the interaction of transporters and channels with protein-trafficking complexes. This review highlights the value in utilizing transporters and channels as cargo to characterize core trafficking machinery by which epithelial cells establish and maintain their polarized expression, and how this machinery regulates fluid and solute transport in response to physiological stimuli.
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Affiliation(s)
- Curtis T Okamoto
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California 90089-9121
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11
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Bertrand CA, Mitra S, Mishra SK, Wang X, Zhao Y, Pilewski JM, Madden DR, Frizzell RA. The CFTR trafficking mutation F508del inhibits the constitutive activity of SLC26A9. Am J Physiol Lung Cell Mol Physiol 2017; 312:L912-L925. [PMID: 28360110 PMCID: PMC5495941 DOI: 10.1152/ajplung.00178.2016] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 03/22/2017] [Accepted: 03/22/2017] [Indexed: 11/22/2022] Open
Abstract
Several members of the SLC26A family of anion transporters associate with CFTR, forming complexes in which CFTR and SLC26A functions are reciprocally regulated. These associations are thought to be facilitated by PDZ scaffolding interactions. CFTR has been shown to be positively regulated by NHERF-1, and negatively regulated by CAL in airway epithelia. However, it is unclear which PDZ-domain protein(s) interact with SLC26A9, a SLC26A family member found in airway epithelia. We have previously shown that primary, human bronchial epithelia (HBE) from non-CF donors exhibit constitutive anion secretion attributable to SLC26A9. However, constitutive anion secretion is absent in HBE from CF donors. We examined whether changes in SLC26A9 constitutive activity could be attributed to a loss of CFTR trafficking, and what role PDZ interactions played. HEK293 coexpressing SLC26A9 with the trafficking mutant F508del CFTR exhibited a significant reduction in constitutive current compared with cells coexpressing SLC26A9 and wt CFTR. We found that SLC26A9 exhibits complex glycosylation when coexpressed with F508del CFTR, but its expression at the plasma membrane is decreased. SLC26A9 interacted with both NHERF-1 and CAL, and its interaction with both significantly increased with coexpression of wt CFTR. However, coexpression with F508del CFTR only increased SLC26A9's interaction with CAL. Mutation of SLC26A9's PDZ motif decreased this association with CAL, and restored its constitutive activity. Correcting aberrant F508del CFTR trafficking in CF HBE with corrector VX-809 also restored SLC26A9 activity. We conclude that when SLC26A9 is coexpressed with F508del CFTR, its trafficking defect leads to a PDZ motif-sensitive intracellular retention of SLC26A9.
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Affiliation(s)
- Carol A Bertrand
- Departments of Pediatrics and Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania;
| | - Shalini Mitra
- Departments of Pediatrics and Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Sanjay K Mishra
- Departments of Pediatrics and Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Xiaohui Wang
- Departments of Pediatrics and Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Yu Zhao
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire
| | - Joseph M Pilewski
- Department of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; and
| | - Dean R Madden
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire
| | - Raymond A Frizzell
- Departments of Pediatrics and Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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12
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Sharma N, LaRusch J, Sosnay PR, Gottschalk LB, Lopez AP, Pellicore MJ, Evans T, Davis E, Atalar M, Na CH, Rosson GD, Belchis D, Milewski M, Pandey A, Cutting GR. A sequence upstream of canonical PDZ-binding motif within CFTR COOH-terminus enhances NHERF1 interaction. Am J Physiol Lung Cell Mol Physiol 2016; 311:L1170-L1182. [PMID: 27793802 DOI: 10.1152/ajplung.00363.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 10/18/2016] [Indexed: 01/10/2023] Open
Abstract
The development of cystic fibrosis transmembrane conductance regulator (CFTR) targeted therapy for cystic fibrosis has generated interest in maximizing membrane residence of mutant forms of CFTR by manipulating interactions with scaffold proteins, such as sodium/hydrogen exchange regulatory factor-1 (NHERF1). In this study, we explored whether COOH-terminal sequences in CFTR beyond the PDZ-binding motif influence its interaction with NHERF1. NHERF1 displayed minimal self-association in blot overlays (NHERF1, Kd = 1,382 ± 61.1 nM) at concentrations well above physiological levels, estimated at 240 nM from RNA-sequencing and 260 nM by liquid chromatography tandem mass spectrometry in sweat gland, a key site of CFTR function in vivo. However, NHERF1 oligomerized at considerably lower concentrations (10 nM) in the presence of the last 111 amino acids of CFTR (20 nM) in blot overlays and cross-linking assays and in coimmunoprecipitations using differently tagged versions of NHERF1. Deletion and alanine mutagenesis revealed that a six-amino acid sequence 1417EENKVR1422 and the terminal 1478TRL1480 (PDZ-binding motif) in the COOH-terminus were essential for the enhanced oligomerization of NHERF1. Full-length CFTR stably expressed in Madin-Darby canine kidney epithelial cells fostered NHERF1 oligomerization that was substantially reduced (∼5-fold) on alanine substitution of EEN, KVR, or EENKVR residues or deletion of the TRL motif. Confocal fluorescent microscopy revealed that the EENKVR and TRL sequences contribute to preferential localization of CFTR to the apical membrane. Together, these results indicate that COOH-terminal sequences mediate enhanced NHERF1 interaction and facilitate the localization of CFTR, a property that could be manipulated to stabilize mutant forms of CFTR at the apical surface to maximize the effect of CFTR-targeted therapeutics.
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Affiliation(s)
- Neeraj Sharma
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Jessica LaRusch
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.,ARIEL Precision Medicine, Pittsburgh, Pennsylvania
| | - Patrick R Sosnay
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Laura B Gottschalk
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Andrea P Lopez
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Matthew J Pellicore
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Taylor Evans
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Emily Davis
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Melis Atalar
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Chan-Hyun Na
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Gedge D Rosson
- Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Deborah Belchis
- Department of Surgical Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland; and
| | - Michal Milewski
- Department of Medical Genetics, Institute of Mother and Child, Warsaw, Poland
| | - Akhilesh Pandey
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Garry R Cutting
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland;
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13
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Chin S, Hung M, Bear CE. Current insights into the role of PKA phosphorylation in CFTR channel activity and the pharmacological rescue of cystic fibrosis disease-causing mutants. Cell Mol Life Sci 2017; 74:57-66. [PMID: 27722768 DOI: 10.1007/s00018-016-2388-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 09/28/2016] [Indexed: 12/21/2022]
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) channel gating is predominantly regulated by protein kinase A (PKA)-dependent phosphorylation. In addition to regulating CFTR channel activity, PKA phosphorylation is also involved in enhancing CFTR trafficking and mediating conformational changes at the interdomain interfaces of the protein. The major cystic fibrosis (CF)-causing mutation is the deletion of phenylalanine at position 508 (F508del); it causes many defects that affect CFTR trafficking, stability, and gating at the cell surface. Due to the multiple roles of PKA phosphorylation, there is growing interest in targeting PKA-dependent signaling for rescuing the trafficking and functional defects of F508del-CFTR. This review will discuss the effects of PKA phosphorylation on wild-type CFTR, the consequences of CF mutations on PKA phosphorylation, and the development of therapies that target PKA-mediated signaling.
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14
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Watson MJ, Lee SL, Marklew AJ, Gilmore RC, Gentzsch M, Sassano MF, Gray MA, Tarran R. The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Uses its C-Terminus to Regulate the A2B Adenosine Receptor. Sci Rep 2016; 6:27390. [PMID: 27278076 DOI: 10.1038/srep27390] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 05/17/2016] [Indexed: 02/08/2023] Open
Abstract
CFTR is an apical membrane anion channel that regulates fluid homeostasis in many organs including the airways, colon, pancreas and sweat glands. In cystic fibrosis, CFTR dysfunction causes significant morbidity/mortality. Whilst CFTR's function as an ion channel has been well described, its ability to regulate other proteins is less understood. We have previously shown that plasma membrane CFTR increases the surface density of the adenosine 2B receptor (A2BR), but not of the β2 adrenergic receptor (β2AR), leading to an enhanced, adenosine-induced cAMP response in the presence of CFTR. In this study, we have found that the C-terminal PDZ-domain of both A2BR and CFTR were crucial for this interaction, and that replacing the C-terminus of A2BR with that of β2AR removed this CFTR-dependency. This observation extended to intact epithelia and disruption of the actin cytoskeleton prevented A2BR-induced but not β2AR-induced airway surface liquid (ASL) secretion. We also found that CFTR expression altered the organization of the actin cytoskeleton and PDZ-binding proteins in both HEK293T cells and in well-differentiated human bronchial epithelia. Furthermore, removal of CFTR's PDZ binding motif (ΔTRL) prevented actin rearrangement, suggesting that CFTR insertion in the plasma membrane results in local reorganization of actin, PDZ binding proteins and certain GPCRs.
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Pokharel D, Padula MP, Lu JF, Jaiswal R, Djordjevic SP, Bebawy M. The Role of CD44 and ERM Proteins in Expression and Functionality of P-glycoprotein in Breast Cancer Cells. Molecules 2016; 21:290. [PMID: 26938523 DOI: 10.3390/molecules21030290] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 02/22/2016] [Accepted: 02/23/2016] [Indexed: 12/19/2022] Open
Abstract
Multidrug resistance (MDR) is often attributed to the over-expression of P-glycoprotein (P-gp), which prevents the accumulation of anticancer drugs within cells by virtue of its active drug efflux capacity. We have previously described the intercellular transfer of P-gp via extracellular vesicles (EVs) and proposed the involvement of a unique protein complex in regulating this process. In this paper, we investigate the role of these mediators in the regulation of P-gp functionality and hence the acquisition of MDR following cell to cell transfer. By sequentially silencing the FERM domain-binding proteins, Ezrin, Radixin and Moesin (ERM), as well as CD44, which we also report a selective packaging in breast cancer derived EVs, we have established a role for these proteins, in particular Radixin and CD44, in influencing the P-gp-mediated MDR in whole cells. We also report for the first time the role of ERM proteins in the vesicular transfer of functional P-gp. Specifically, we demonstrate that intercellular membrane insertion is dependent on Ezrin and Moesin, whilst P-gp functionality is governed by the integrity of all ERM proteins in the recipient cell. This study identifies these candidate proteins as potential new therapeutic targets in circumventing MDR clinically.
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16
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Venot Q, Delaunay JL, Fouassier L, Delautier D, Falguières T, Housset C, Maurice M, Aït-Slimane T. A PDZ-Like Motif in the Biliary Transporter ABCB4 Interacts with the Scaffold Protein EBP50 and Regulates ABCB4 Cell Surface Expression. PLoS One 2016; 11:e0146962. [PMID: 26789121 PMCID: PMC4720445 DOI: 10.1371/journal.pone.0146962] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 12/23/2015] [Indexed: 12/11/2022] Open
Abstract
ABCB4/MDR3, a member of the ABC superfamily, is an ATP-dependent phosphatidylcholine translocator expressed at the canalicular membrane of hepatocytes. Defects in the ABCB4 gene are associated with rare biliary diseases. It is essential to understand the mechanisms of its canalicular membrane expression in particular for the development of new therapies. The stability of several ABC transporters is regulated through their binding to PDZ (PSD95/DglA/ZO-1) domain-containing proteins. ABCB4 protein ends by the sequence glutamine-asparagine-leucine (QNL), which shows some similarity to PDZ-binding motifs. The aim of our study was to assess the potential role of the QNL motif on the surface expression of ABCB4 and to determine if PDZ domain-containing proteins are involved. We found that truncation of the QNL motif decreased the stability of ABCB4 in HepG2-transfected cells. The deleted mutant ABCB4-ΔQNL also displayed accelerated endocytosis. EBP50, a PDZ protein highly expressed in the liver, strongly colocalized and coimmunoprecipitated with ABCB4, and this interaction required the QNL motif. Down-regulation of EBP50 by siRNA or by expression of an EBP50 dominant-negative mutant caused a significant decrease in the level of ABCB4 protein expression, and in the amount of ABCB4 localized at the canalicular membrane. Interaction of ABCB4 with EBP50 through its PDZ-like motif plays a critical role in the regulation of ABCB4 expression and stability at the canalicular plasma membrane.
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Affiliation(s)
- Quitterie Venot
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France
| | - Jean-Louis Delaunay
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France
| | - Laura Fouassier
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France
| | - Danièle Delautier
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France
| | - Thomas Falguières
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France
| | - Chantal Housset
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France
- Assistance Publique-Hôpitaux de Paris, Hôpital Saint-Antoine, Centre de Référence Maladies Rares Maladies Inflammatoires des Voies Biliaires & Service d’Hépatologie, Paris, France
| | - Michèle Maurice
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France
| | - Tounsia Aït-Slimane
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France
- * E-mail:
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17
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Monterisi S, Casavola V, Zaccolo M. Local modulation of cystic fibrosis conductance regulator: cytoskeleton and compartmentalized cAMP signalling. Br J Pharmacol 2014; 169:1-9. [PMID: 23072488 DOI: 10.1111/bph.12017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 09/12/2012] [Accepted: 10/05/2012] [Indexed: 11/28/2022] Open
Abstract
The cystic fibrosis conductance regulator (CFTR) is a cAMP-regulated Cl(-) channel expressed predominantly at the apical membrane of secreting epithelial cells. Mutations in the CFTR gene lead to cystic fibrosis, the most frequent genetic disease in the Caucasian population. The most common mutation, a deletion of phenylalanine at position 508 (F508del), impairs CFTR folding and chloride channel function. Although an intense effort is under way to identify compounds that target the F508del CFTR structural defect and promote its expression and stability at the plasma membrane, so far their clinical efficacy has proven to be poor, highlighting the necessity to better understand the molecular mechanism of CFTR regulation and of the pathogenesis of the disease. Accumulating evidence suggests that the inclusion of the CFTR in macromolecular complexes and its interaction with the cortical cytoskeleton may play a key role in fine-tuning the regulation of channel function. Here we review some recent findings that support a critical role for protein-protein interactions involving CFTR and for the cytoskeleton in promoting local control of channel activity. These findings indicate that compounds that rescue and stabilize CFTR at the apical membrane may not be sufficient to restore its function unless the appropriate intracellular milieu is also reconstituted.
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Affiliation(s)
- Stefania Monterisi
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford, UK
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Koeppen K, Coutermarsh BA, Madden DR, Stanton BA. Serum- and glucocorticoid-induced protein kinase 1 (SGK1) increases the cystic fibrosis transmembrane conductance regulator (CFTR) in airway epithelial cells by phosphorylating Shank2E protein. J Biol Chem 2014; 289:17142-50. [PMID: 24811177 DOI: 10.1074/jbc.m114.555599] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The glucocorticoid dexamethasone increases cystic fibrosis transmembrane conductance regulator (CFTR) abundance in human airway epithelial cells by a mechanism that requires serum- and glucocorticoid-induced protein kinase 1 (SGK1) activity. The goal of this study was to determine whether SGK1 increases CFTR abundance by phosphorylating Shank2E, a PDZ domain protein that contains two SGK1 phosphorylation consensus sites. We found that SGK1 phosphorylates Shank2E as well as a peptide containing the first SGK1 consensus motif of Shank2E. The dexamethasone-induced increase in CFTR abundance was diminished by overexpression of a dominant-negative Shank2E in which the SGK1 phosphorylation sites had been mutated. siRNA-mediated reduction of Shank2E also reduced the dexamethasone-induced increase in CFTR abundance. Taken together, these data demonstrate that the glucocorticoid-induced increase in CFTR abundance requires phosphorylation of Shank2E at an SGK1 consensus site.
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Affiliation(s)
- Katja Koeppen
- From the Department of Microbiology and Immunology and
| | | | - Dean R Madden
- Department of Biochemistry, The Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755
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Smith L, Litman P, Kohli E, Amick J, Page RC, Misra S, Liedtke CM. RACK1 interacts with filamin-A to regulate plasma membrane levels of the cystic fibrosis transmembrane conductance regulator. Am J Physiol Cell Physiol 2013; 305:C111-20. [PMID: 23636454 PMCID: PMC3725521 DOI: 10.1152/ajpcell.00026.2013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 04/25/2013] [Indexed: 01/27/2023]
Abstract
Mutations in cystic fibrosis transmembrane regulator (CFTR), a chloride channel in the apical membranes of secretory epithelial cells, underlie the fatal genetic disorder cystic fibrosis. Certain CFTR mutations, including the common mutation ΔF508-CFTR, result in greatly decreased levels of active CFTR at the apical membrane. Direct interactions between CFTR and the cytoskeletal adaptors filamin-A (FlnA) and Na(+)/H(+) exchanger regulatory factor 1 (NHERF1) stabilize the expression and localization of CFTR at the plasma membrane. The scaffold protein receptor for activated C kinase 1 (RACK1) also stabilizes CFTR surface expression; however, RACK1 does not interact directly with CFTR and its mechanism of action is unknown. In the present study, we report that RACK1 interacts directly with FlnA in vitro and in a Calu-3 airway epithelial cell line. We mapped the interaction between RACK1 and FlnA to the WD4 and WD6 repeats of RACK1 and to a segment of the large rod domain of FlnA, consisting of immunoglobulin-like repeats 8-15. Disruption of the RACK1-FlnA interaction causes a reduction in CFTR surface levels. Our results suggest that a novel RACK1-FlnA interaction is an important regulator of CFTR surface localization.
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Affiliation(s)
- Laura Smith
- Willard Alan Bernbaum Center for Cystic Fibrosis Research, Case Western Reserve University, Cleveland, OH 44106, USA
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20
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Pelaseyed T, Gustafsson JK, Gustafsson IJ, Ermund A, Hansson GC. Carbachol-induced MUC17 endocytosis is concomitant with NHE3 internalization and CFTR membrane recruitment in enterocytes. Am J Physiol Cell Physiol 2013; 305:C457-67. [PMID: 23784542 DOI: 10.1152/ajpcell.00141.2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have reported that transmembrane mucin MUC17 binds PDZ protein PDZK1, which retains MUC17 apically in enterocytes. MUC17 and transmembrane mucins MUC3 and MUC12 are suggested to build the enterocyte apical glycocalyx. Carbachol (CCh) stimulation of the small intestine results in gel-forming mucin secretion from goblet cells, something that requires adjacent enterocytes to secrete chloride and bicarbonate for proper mucin formation. Surface labeling and confocal imaging demonstrated that apically expressed MUC17 in Caco-2 cells and Muc3(17) in murine enterocytes were endocytosed upon stimulation with CCh. Relocation of MUC17 in response to CCh was specific as MUC3 and MUC12 did not relocate following CCh stimulation. MUC17 colocalized with PDZK1 under basal conditions, while MUC17 relocated to the terminal web and into early endosomes after CCh stimulation. CCh stimulation concomitantly internalized the Na(+/)H(+) exchanger 3 (NHE3) and recruited cystic fibrosis transmembrane conductance regulator (CFTR) to the apical membranes, a process that was important for CFTR-mediated bicarbonate secretion necessary for proper gel-forming mucin unfolding. The reason for the specific internalization of MUC17 is not understood, but it could limit the diffusion barrier for ion secretion caused by the apical enterocyte glycocalyx or alternatively act to sample luminal bacteria. Our results reveal well-orchestrated mucus secretion and trafficking of ion channels and the MUC17 mucin.
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Affiliation(s)
- Thaher Pelaseyed
- Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden
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21
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Bhattacharya S, Ju JH, Orlova N, Khajeh JA, Cowburn D, Bu Z. Ligand-induced dynamic changes in extended PDZ domains from NHERF1. J Mol Biol 2013; 425:2509-28. [PMID: 23583913 DOI: 10.1016/j.jmb.2013.04.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Revised: 03/31/2013] [Accepted: 04/03/2013] [Indexed: 01/09/2023]
Abstract
The multi-domain scaffolding protein NHERF1 modulates the assembly and intracellular trafficking of various transmembrane receptors and ion-transport proteins. The two PDZ (postsynaptic density 95/disk large/zonula occluden 1) domains of NHERF1 possess very different ligand-binding capabilities: PDZ1 recognizes a variety of membrane proteins with high affinity, while PDZ2 only binds limited number of target proteins. Here using NMR, we have determined the structural and dynamic mechanisms that differentiate the binding affinities of the two PDZ domains, for the type 1 PDZ-binding motif (QDTRL) in the carboxyl terminus of cystic fibrosis transmembrane regulator. Similar to PDZ2, we have identified a helix-loop-helix subdomain coupled to the canonical PDZ1 domain. The extended PDZ1 domain is highly flexible with correlated backbone motions on fast and slow timescales, while the extended PDZ2 domain is relatively rigid. The malleability of the extended PDZ1 structure facilitates the transmission of conformational changes at the ligand-binding site to the remote helix-loop-helix extension. By contrast, ligand binding has only modest effects on the conformation and dynamics of the extended PDZ2 domain. The study shows that ligand-induced structural and dynamic changes coupled with sequence variation at the putative PDZ binding site dictate ligand selectivity and binding affinity of the two PDZ domains of NHERF1.
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Lee HW, Cheng J, Kovbasnjuk O, Donowitz M, Guggino WB. Insulin-like growth factor 1 (IGF-1) enhances the protein expression of CFTR. PLoS One 2013; 8:e59992. [PMID: 23555857 DOI: 10.1371/journal.pone.0059992] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 02/25/2013] [Indexed: 11/19/2022] Open
Abstract
Low levels of insulin-like growth factor 1 (IGF-1) have been observed in the serum of cystic fibrosis (CF) patients. However, the effects of low serum IGF-1 on the cystic fibrosis transmembrane conductance regulator (CFTR), whose defective function is the primary cause of cystic fibrosis, have not been studied. Here, we show in human cells that IGF-1 increases the steady-state levels of mature wildtype CFTR in a CFTR-associated ligand (CAL)- and TC10-dependent manner; moreover, IGF-1 increases CFTR-mediated chloride transport. Using an acceptor photobleaching fluorescence resonance energy transfer (FRET) assay, we have confirmed the binding of CAL and CFTR in the Golgi. We also show that CAL overexpression inhibits forskolin-induced increases in the cell-surface expression of CFTR. We found that IGF-1 activates TC10, and active TC10 alters the functional association between CAL and CFTR. Furthermore, IGF-1 and active TC10 can reverse the CAL-mediated reduction in the cell-surface expression of CFTR. IGF-1 does not increase the expression of ΔF508 CFTR, whose processing is arrested in the ER. This finding is consistent with our observation that IGF-1 alters the functional interaction of CAL and CFTR in the Golgi. However, when ΔF508 CFTR is rescued with low temperature or the corrector VRT-325 and proceeds to the Golgi, IGF-1 can increase the expression of the rescued ΔF508 CFTR. Our data support a model indicating that CAL-CFTR binding in the Golgi inhibits CFTR trafficking to the cell surface, leading CFTR to the degradation pathway instead. IGF-1-activated TC10 changes the interaction of CFTR and CAL, allowing CFTR to progress to the plasma membrane. These findings offer a potential strategy using a combinational treatment of IGF-1 and correctors to increase the post-Golgi expression of CFTR in cystic fibrosis patients bearing the ΔF508 mutation.
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Ren A, Zhang W, Yarlagadda S, Sinha C, Arora K, Moon CS, Naren AP. MAST205 competes with cystic fibrosis transmembrane conductance regulator (CFTR)-associated ligand for binding to CFTR to regulate CFTR-mediated fluid transport. J Biol Chem 2013; 288:12325-34. [PMID: 23504457 DOI: 10.1074/jbc.m112.432724] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The PDZ (postsynaptic density-95/discs large/zona occludens-1) domain-based interactions play important roles in regulating the expression and function of the cystic fibrosis transmembrane conductance regulator (CFTR). Several PDZ domain-containing proteins (PDZ proteins for short) have been identified as directly or indirectly interacting with the C terminus of CFTR. To better understand the regulation of CFTR processing, we conducted a genetic screen and identified MAST205 (a microtubule-associated serine/threonine kinase with a molecular mass of 205 kDa) as a new CFTR regulator. We found that overexpression of MAST205 increased the expression of CFTR and augmented CFTR-mediated fluid transport in a dose-dependent manner. Conversely, knockdown of MAST205 inhibited CFTR function. The PDZ motif of CFTR is required for the regulatory role of MAST205 in CFTR expression and function. We further demonstrated that MAST205 and the CFTR-associated ligand competed for binding to CFTR, which facilitated the processing of CFTR and consequently up-regulated the expression and function of CFTR at the plasma membrane. More importantly, we found that MAST205 could facilitate the processing of F508del-CFTR mutant and augment its quantity and channel function at the plasma membrane. Taken together, our data suggest that MAST205 plays an important role in regulating CFTR expression and function. Our findings have important clinical implications for treating CFTR-associated diseases such as cystic fibrosis and secretory diarrheas.
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Affiliation(s)
- Aixia Ren
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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24
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Korb D, Tng PY, Milenkovic VM, Reichhart N, Strauss O, Ritter O, Fischer T, Benz PM, Schuh K. Identification of PDZ Domain Containing Proteins Interacting with 1.2 and PMCA4b. ACTA ACUST UNITED AC 2013; 2013:1-16. [DOI: 10.1155/2013/265182] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PDZ (PSD-95/Disc large/Zonula occludens-1) protein interaction domains bind to cytoplasmic protein C-termini of transmembrane proteins. In order to identify new interaction partners of the voltage-gated L-type Ca2+ channel 1.2 and the plasma membrane Ca2+ ATPase 4b (PMCA4b), we used PDZ domain arrays probing for 124 PDZ domains. We confirmed this by GST pull-downs and immunoprecipitations. In PDZ arrays, strongest interactions with 1.2 and PMCA4b were found for the PDZ domains of SAP-102, MAST-205, MAGI-1, MAGI-2, MAGI-3, and ZO-1. We observed binding of the 1.2 C-terminus to PDZ domains of NHERF1/2, Mint-2, and CASK. PMCA4b was observed to interact with Mint-2 and its known interactions with Chapsyn-110 and CASK were confirmed. Furthermore, we validated interaction of 1.2 and PMCA4b with NHERF1/2, CASK, MAST-205 and MAGI-3 via immunoprecipitation. We also verified the interaction of 1.2 and nNOS and hypothesized that nNOS overexpression might reduce Ca2+ influx through 1.2. To address this, we measured Ca2+ currents in HEK 293 cells co-expressing 1.2 and nNOS and observed reduced voltage-dependent 1.2 activation. Taken together, we conclude that 1.2 and PMCA4b bind promiscuously to various PDZ domains, and that our data provides the basis for further investigation of the physiological consequences of these interactions.
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Molinski S, Eckford PDW, Pasyk S, Ahmadi S, Chin S, Bear CE. Functional Rescue of F508del-CFTR Using Small Molecule Correctors. Front Pharmacol 2012; 3:160. [PMID: 23055971 PMCID: PMC3458236 DOI: 10.3389/fphar.2012.00160] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 08/17/2012] [Indexed: 01/21/2023] Open
Abstract
High-throughput screens for small molecules that are effective in “correcting” the functional expression of F508del-CFTR have yielded several promising hits. Two such compounds are currently in clinical trial. Despite this success, it is clear that further advances will be required in order to restore 50% or greater of wild-type CFTR function to the airways of patients harboring the F508del-CFTR protein. Progress will be enhanced by our better understanding of the molecular and cellular defects caused by the F508del mutation, present in 90% of CF patients. The goal of this chapter is to review the current understanding of defects caused by F508del in the CFTR protein and in CFTR-mediated interactions important for its biosynthesis, trafficking, channel function, and stability at the cell surface. Finally, we will discuss the gaps in our knowledge regarding the mechanism of action of existing correctors, the unmet need to discover compounds which restore proper CFTR structure and function in CF affected tissues and new strategies for therapy development.
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Affiliation(s)
- Steven Molinski
- Programme in Molecular Structure and Function, Research Institute, Hospital for Sick Children Toronto, ON, Canada ; Department of Biochemistry, University of Toronto Toronto, ON, Canada
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Dupré DJ, Rola-Pleszczynski M, Stankova J. Rescue of internalization-defective platelet-activating factor receptor function by EBP50/NHERF1. J Cell Commun Signal 2012; 6:205-16. [PMID: 22878922 DOI: 10.1007/s12079-012-0175-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 08/01/2012] [Indexed: 12/20/2022] Open
Abstract
Platelet-activating factor (PAF) is a potent phospholipid mediator involved in specific disease states such as allergic asthma, atherosclerosis and psoriasis. The human PAF receptor (PAFR) is a member of the G protein-coupled receptor (GPCR) family. Following PAF stimulation, cells become rapidly desensitized; this refractory state can be maintained for hours and is dependent on PAFR phosphorylation, internalization and trafficking. EBP50/NHERF1 has been found to interact with a variety of proteins and these interactions are involved in a growing range of functions including the assembly of signalling complexes, receptor recycling and transport of proteins to the cell surface. Crucial roles of EBP50 in GPCR physiology include its involvement in internalization, recycling, and downregulation. We were interested in identifying the role of EBP50 in PAFR trafficking. Our results showed that EBP50 binds the PAFR in its basal state, while stimulation decreased the ratio of interaction between the two proteins. We also demonstrated that EBP50 could bind PAFR via its PDZ 2 domain. In addition, we studied the role of EBP50 in various functions of the PAFR such as PAF-induced inositol phosphate accumulation and receptor internalization: EBP50 decreased the WT PAFR response and rescued the function of internalization-deficient mutant receptors, as previously described for the arrestins and the GRKs. These results suggest new roles for EBP50, some of which could help understanding the complex formation after receptor activation.
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Affiliation(s)
- Denis J Dupré
- Department of Pharmacology, Faculty of Medicine, Dalhousie University, 5850 College St., PO BOX 15000, Halifax, NS, B3H 4R2, Canada,
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Monterisi S, Favia M, Guerra L, Cardone RA, Marzulli D, Reshkin SJ, Casavola V, Zaccolo M. CFTR regulation in human airway epithelial cells requires integrity of the actin cytoskeleton and compartmentalized cAMP and PKA activity. J Cell Sci 2012; 125:1106-17. [PMID: 22302988 DOI: 10.1242/jcs.089086] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) mutation ΔF508CFTR still causes regulatory defects when rescued to the apical membrane, suggesting that the intracellular milieu might affect its ability to respond to cAMP regulation. We recently reported that overexpression of the Na(+)/H(+) exchanger regulatory factor NHERF1 in the cystic fibrosis (CF) airway cell line CFBE41o-rescues the functional expression of ΔF508CFTR by promoting F-actin organization and formation of the NHERF1-ezrin-actin complex. Here, using real-time FRET reporters of both PKA activity and cAMP levels, we find that lack of an organized subcortical cytoskeleton in CFBE41o-cells causes both defective accumulation of cAMP in the subcortical compartment and excessive cytosolic accumulation of cAMP. This results in reduced subcortical levels and increased cytosolic levels of PKA activity. NHERF1 overexpression in CFBE41o-cells restores chloride secretion, subcortical cAMP compartmentalization and local PKA activity, indicating that regulation of ΔF508CFTR function requires not only stable expression of the mutant CFTR at the cell surface but also depends on both generation of local cAMP signals of adequate amplitude and activation of PKA in proximity of its target. Moreover, we found that the knockdown of wild-type CFTR in the non-CF 16HBE14o-cells results in both altered cytoskeletal organization and loss of cAMP compartmentalization, whereas stable overexpression of wt CFTR in CF cells restores cytoskeleton organization and re-establishes the compartmentalization of cAMP at the plasma membrane. This suggests that the presence of CFTR on the plasma membrane influences the cytoskeletal organizational state and, consequently, cAMP distribution. Our data show that a sufficiently high concentration of cAMP in the subcortical compartment is required to achieve PKA-mediated regulation of CFTR activity.
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Affiliation(s)
- Stefania Monterisi
- Department of General and Environmental Physiology, University of Bari, Bari, 70125, Italy
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Bodas M, Min T, Mazur S, Vij N. Critical modifier role of membrane-cystic fibrosis transmembrane conductance regulator-dependent ceramide signaling in lung injury and emphysema. J Immunol 2010; 186:602-13. [PMID: 21135173 DOI: 10.4049/jimmunol.1002850] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ceramide accumulation mediates the pathogenesis of chronic obstructive lung diseases. Although an association between lack of cystic fibrosis transmembrane conductance regulator (CFTR) and ceramide accumulation has been described, it is unclear how membrane-CFTR may modulate ceramide signaling in lung injury and emphysema. Cftr(+/+) and Cftr(-/-) mice and cells were used to evaluate the CFTR-dependent ceramide signaling in lung injury. Lung tissue from control and chronic obstructive pulmonary disease patients was used to verify the role of CFTR-dependent ceramide signaling in pathogenesis of chronic emphysema. Our data reveal that CFTR expression inversely correlates with severity of emphysema and ceramide accumulation in chronic obstructive pulmonary disease subjects compared with control subjects. We found that chemical inhibition of de novo ceramide synthesis controls Pseudomonas aeruginosa-LPS-induced lung injury in Cftr(+/+) mice, whereas its efficacy was significantly lower in Cftr(-/-) mice, indicating that membrane-CFTR is required for controlling lipid-raft ceramide levels. Inhibition of membrane-ceramide release showed enhanced protective effect in controlling P. aeruginosa-LPS-induced lung injury in Cftr(-/-) mice compared with that in Cftr(+/+) mice, confirming our observation that CFTR regulates lipid-raft ceramide levels and signaling. Our results indicate that inhibition of de novo ceramide synthesis may be effective in disease states with low CFTR expression like emphysema and chronic lung injury but not in complete absence of lipid-raft CFTR as in ΔF508-cystic fibrosis. In contrast, inhibiting membrane-ceramide release has the potential of a more effective drug candidate for ΔF508-cystic fibrosis but may not be effectual in treating lung injury and emphysema. Our data demonstrate the critical role of membrane-localized CFTR in regulating ceramide accumulation and inflammatory signaling in lung injury and emphysema.
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Affiliation(s)
- Manish Bodas
- Department of Pediatric Respiratory Sciences, Johns Hopkins University, Baltimore, MD 21287, USA
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Hammad MM, Kuang YQ, Yan R, Allen H, Dupré DJ. Na+/H+ exchanger regulatory factor-1 is involved in chemokine receptor homodimer CCR5 internalization and signal transduction but does not affect CXCR4 homodimer or CXCR4-CCR5 heterodimer. J Biol Chem 2010; 285:34653-64. [PMID: 20801883 PMCID: PMC2966081 DOI: 10.1074/jbc.m110.106591] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 08/25/2010] [Indexed: 11/06/2022] Open
Abstract
Chemokine receptors are members of the G protein-coupled receptor (GPCR) family. CCR5 is also the principal co-receptor for macrophage-tropic strains of human immunodeficiency virus, type 1 (HIV-1), and efforts have been made to develop ligands to inhibit HIV-1 infection by promoting CCR5 receptor endocytosis. Given the nature of GPCRs and their propensity to form oligomers, one can consider ligand-based therapies as unselective in terms of the oligomeric composition of complexes. For example, a ligand targeting a CCR5 homomer could likely induce signal transduction on a heteromeric CCR5-CXCR4. Other avenues could therefore be explored. We identified a receptor adaptor interacting specifically with one receptor complex but not others. NHERF1, an adaptor known for its role in desensitization, internalization, and regulation of the ERK signaling cascade for several GPCRs, interacts via its PDZ2 domain with the CCR5 homodimer but not with the CXCR4-CCR5 heterodimer or CXCR4 homodimer. To further characterize this interaction, we also show that NHERF1 increases the CCR5 recruitment of arrestin2 following stimulation. NHERF1 is also involved in CCR5 internalization, as we demonstrate that co-expression of constructs bearing the PDZ2 domain can block CCR5 internalization. We also show that NHERF1 potentiates RANTES (regulated on activation normal T cell expressed and secreted)-induced ERK1/2 phosphorylation via CCR5 activation and that this activation requires NHERF1 but not arrestin2. Taken together, our results suggest that oligomeric receptor complexes can associate specifically with partners and that in this case NHERF1 could represent an interesting new target for the regulation of CCR5 internalization and potentially HIV infection.
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Affiliation(s)
- Maha M. Hammad
- From the Department of Pharmacology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada
| | - Yi-Qun Kuang
- From the Department of Pharmacology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada
| | - Ronald Yan
- From the Department of Pharmacology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada
| | - Heather Allen
- From the Department of Pharmacology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada
| | - Denis J. Dupré
- From the Department of Pharmacology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada
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30
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Padányi R, Xiong Y, Antalffy G, Lór K, Pászty K, Strehler EE, Enyedi A. Apical scaffolding protein NHERF2 modulates the localization of alternatively spliced plasma membrane Ca2+ pump 2B variants in polarized epithelial cells. J Biol Chem 2010; 285:31704-12. [PMID: 20663896 DOI: 10.1074/jbc.m110.164137] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The membrane localization of the plasma membrane Ca(2+)-ATPase isoform 2 (PMCA2) in polarized cells is determined by alternative splicing; the PMCA2w/b splice variant shows apical localization, whereas the PMCA2z/b and PMCA2x/b variants are mostly basolateral. We previously reported that PMCA2b interacts with the PDZ protein Na(+)/H(+) exchanger regulatory factor 2 (NHERF2), but the role of this interaction for the specific membrane localization of PMCA2 is not known. Here we show that co-expression of NHERF2 greatly enhanced the apical localization of GFP-tagged PMCA2w/b in polarized Madin-Darby canine kidney cells. GFP-PMCA2z/b was also redirected to the apical membrane by NHERF2, whereas GFP-PMCA2x/b remained exclusively basolateral. In the presence of NHERF2, GFP-PMCA2w/b co-localized with the actin-binding protein ezrin even after disruption of the actin cytoskeleton by cytochalasin D or latrunculin B. Surface biotinylation and fluorescence recovery after photobleaching experiments demonstrated that NHERF2-mediated anchorage to the actin cytoskeleton reduced internalization and lateral mobility of the pump. Our results show that the specific interaction with NHERF2 enhances the apical concentration of PMCA2w/b by anchoring the pump to the apical membrane cytoskeleton. The data also suggest that the x/b splice form of PMCA2 contains a dominant lateral targeting signal, whereas the targeting and localization of the z/b form are more flexible and not fully determined by intrinsic sequence features.
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Affiliation(s)
- Rita Padányi
- Department of Molecular Cell Biology, National Blood Center, H-1113 Budapest, Hungary
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31
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Favia M, Guerra L, Fanelli T, Cardone RA, Monterisi S, Di Sole F, Castellani S, Chen M, Seidler U, Reshkin SJ, Conese M, Casavola V. Na+/H+ exchanger regulatory factor 1 overexpression-dependent increase of cytoskeleton organization is fundamental in the rescue of F508del cystic fibrosis transmembrane conductance regulator in human airway CFBE41o- cells. Mol Biol Cell 2009; 21:73-86. [PMID: 19889841 PMCID: PMC2801722 DOI: 10.1091/mbc.e09-03-0185] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
NHERF1 overexpression increases functional apical expression of F508del CFTR in CFBE41o- cells. Here, we show that this occurs via the formation of the multiprotein complex NHERF1-phosphoezrin-actin, which provides a regulated linkage between F508del CFTR and the actin cytoskeleton resulting in an increased F508del CFTR stability in the membrane. We have demonstrated that Na+/H+ exchanger regulatory factor 1 (NHERF1) overexpression in CFBE41o- cells induces a significant redistribution of F508del cystic fibrosis transmembrane conductance regulator (CFTR) from the cytoplasm to the apical membrane and rescues CFTR-dependent chloride secretion. Here, we observe that CFBE41o- monolayers displayed substantial disassembly of actin filaments and that overexpression of wild-type (wt) NHERF1 but not NHERF1-Δ Ezrin-Radixin-Moesin (ERM) increased F-actin assembly and organization. Furthermore, the dominant-negative band Four-point one, Ezrin, Radixin, Moesin homology (FERM) domain of ezrin reversed the wt NHERF1 overexpression-induced increase in both F-actin and CFTR-dependent chloride secretion. wt NHERF1 overexpression enhanced the interaction between NHERF1 and both CFTR and ezrin and between ezrin and actin and the overexpression of wt NHERF1, but not NHERF1-ΔERM, also increased the phosphorylation of ezrin in the apical region of the cell monolayers. Furthermore, wt NHERF1 increased RhoA activity and transfection of constitutively active RhoA in CFBE41o- cells was sufficient to redistribute phospho-ezrin to the membrane fraction and rescue both the F-actin content and the CFTR-dependent chloride efflux. Rho kinase (ROCK) inhibition, in contrast, reversed the wt NHERF1 overexpression-induced increase of membrane phospho-ezrin, F-actin content, and CFTR-dependent secretion. We conclude that NHERF1 overexpression in CFBE41o- rescues CFTR-dependent chloride secretion by forming the multiprotein complex RhoA-ROCK-ezrin-actin that, via actin cytoskeleton reorganization, tethers F508del CFTR to the cytoskeleton stabilizing it on the apical membrane.
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Affiliation(s)
- Maria Favia
- Department of General and Environmental Physiology, University of Bari, Bari, Italy
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32
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Singh AK, Riederer B, Krabbenhöft A, Rausch B, Bonhagen J, Lehmann U, de Jonge HR, Donowitz M, Yun C, Weinman EJ, Kocher O, Hogema BM, Seidler U. Differential roles of NHERF1, NHERF2, and PDZK1 in regulating CFTR-mediated intestinal anion secretion in mice. J Clin Invest 2009; 119:540-50. [PMID: 19221439 DOI: 10.1172/jci35541] [Citation(s) in RCA: 293] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Accepted: 01/07/2009] [Indexed: 01/29/2023] Open
Abstract
The epithelial anion channel CFTR interacts with multiple PDZ domain-containing proteins. Heterologous expression studies have demonstrated that the Na+/H+ exchanger regulatory factors, NHERF1, NHERF2, and PDZK1 (NHERF3), modulate CFTR membrane retention, conductivity, and interactions with other transporters. To study their biological roles in vivo, we investigated CFTR-dependent duodenal HCO3- secretion in mouse models of Nherf1, Nherf2, and Pdzk1 loss of function. We found that Nherf1 ablation strongly reduced basal as well as forskolin-stimulated (FSK-stimulated) HCO3- secretory rates and blocked beta2-adrenergic receptor (beta2-AR) stimulation. Conversely, Nherf2-/- mice displayed augmented FSK-stimulated HCO3- secretion. Furthermore, although lysophosphatidic acid (LPA) inhibited FSK-stimulated HCO3- secretion in WT mice, this effect was lost in Nherf2-/- mice. Pdzk1 ablation reduced basal, but not FSK-stimulated, HCO3- secretion. In addition, laser microdissection and quantitative PCR revealed that the beta2-AR and the type 2 LPA receptor were expressed together with CFTR in duodenal crypts and that colocalization of the beta2-AR and CFTR was reduced in the Nherf1-/- mice. These data suggest that the NHERF proteins differentially modulate duodenal HCO3- secretion: while NHERF1 is an obligatory linker for beta2-AR stimulation of CFTR, NHERF2 confers inhibitory signals by coupling the LPA receptor to CFTR.
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Affiliation(s)
- Anurag Kumar Singh
- Department of Gastroenterology, Hepatology, and Endocrinology, Carl-Neuberg-Strasse 1, Hannover Medical School, Hannover, Germany
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33
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Dudez T, Borot F, Huang S, Kwak BR, Bacchetta M, Ollero M, Stanton BA, Chanson M. CFTR in a lipid raft-TNFR1 complex modulates gap junctional intercellular communication and IL-8 secretion. Biochim Biophys Acta 2008; 1783:779-88. [PMID: 18255040 DOI: 10.1016/j.bbamcr.2008.01.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 01/08/2008] [Accepted: 01/09/2008] [Indexed: 11/25/2022]
Abstract
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) cause a chronic inflammatory response in the lung of patients with Cystic Fibrosis (CF). We have showed that TNF-alpha signaling through the Src family tyrosine kinases (SFKs) was defective as determined by an inability of TNF-alpha to regulate gap junctional communication (GJIC) in CF cells. Here, we sought to elucidate the mechanisms linking TNF-alpha signaling to the functions of CFTR at the molecular level. In a MDCKI epithelial cell model expressing wild-type (WtCFTR) or mutant CFTR lacking its PDZ-interacting motif (CFTR-DeltaTRL), TNF-alpha increased the amount of WtCFTR but not CFTR-DeltaTRL in detergent-resistant membrane microdomains (DRMs). This recruitment was modulated by SFK activity and associated with DRM localization of TNFR1 and c-Src. Activation of TNFR1 signaling also decreased GJIC and markedly stimulated IL-8 production in WtCFTR cells. In contrast, the absence of CFTR in DRMs was associated with abnormal TNFR1 signaling as revealed by no recruitment of TNFR1 and c-Src to lipid rafts in CFTR-DeltaTRL cells and loss of regulation of GJIC and IL-8 secretion. These results suggest that localization of CFTR in lipid rafts in association with c-Src and TNFR1 provides a responsive signaling complex to regulate GJIC and cytokine signaling.
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Affiliation(s)
- Tecla Dudez
- Laboratory of Clinical Investigation III, Micheli-du-Crest, Geneva, Switzerland
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34
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Abstract
Cystic fibrosis results from mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Premature termination codons represent a common minority of CFTR mutations, and are caused by base pair substitutions that produce abnormal stop codons in the coding sequence. Select aminoglycosides induce "translational readthrough" of premature stop codons and have been shown to restore full-length functional protein in a number of preclinical and clinical settings. We studied two well-described premature termination codons found in the distal open reading frame of CFTR, W1282X and R1162X, expressed in polarizing and nonpolarizing cells. Our findings indicate that W1282X CFTR-expressing cells demonstrate significantly greater CFTR activity when overexpressed compared with R1162X CFTR cells, even when truncated protein is the predominant form. In addition, our results show that the combination of stimulated expression and stop codon suppression produces additive effects on CFTR-mediated ion transport. These findings provide evidence that W1282X CFTR exhibits membrane localization and retained chloride channel function after enhanced expression, and suggest that patients harboring this mutation may be more susceptible to CFTR rescue.
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Affiliation(s)
- Steven M Rowe
- Department of Medicine, Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama 35294-0006, USA.
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35
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Bąk D, Cutting GR, Milewski M. The CFTR-derived peptides as a model of sequence-specific protein aggregation. Cell Mol Biol Lett 2007; 12:435-47. [PMID: 17361366 PMCID: PMC6275903 DOI: 10.2478/s11658-007-0014-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Accepted: 01/26/2007] [Indexed: 12/02/2022] Open
Abstract
Protein aggregation is a hallmark of a growing group of pathologies known as conformational diseases. Although many native or mutated proteins are able to form aggregates, the exact amino acid sequences involved in the process of aggregation are known only in a few cases. Hence, there is a need for different model systems to expand our knowledge in this area. The so-called ag region was previously found to cause the aggregation of the C-terminal fragment of the cystic fibrosis transmembrane conductance regulator (CFTR). To investigate whether this specific amino acid sequence is able to induce protein aggregation irrespective of the amino acid context, we altered its position within the CFTR-derived C-terminal peptide and analyzed the localization of such modified peptides in transfected mammalian cells. Insertion of the ag region into a different amino acid background affected not only the overall level of intracellular protein aggregation, but also the morphology and subcellular localization of aggregates, suggesting that sequences other than the ag region can substantially influence the peptide’s behavior. Also, the introduction of a short dipeptide (His-Arg) motif, a crucial component of the ag region, into different locations within the C-terminus of CFTR lead to changes in the aggregation pattern that were less striking, although still statistically significant. Thus, our results indicate that even subtle alterations within the aggregating peptide can affect many different aspects of the aggregation process.
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Affiliation(s)
- Daniel Bąk
- Laboratory of Cell Biology, Department of Medical Genetics, Institute of Mother and Child, Kasprzaka 17A, 01-211, Warsaw, Poland.
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36
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Tandon C, De Lisle RC, Boulatnikov I, Naik PK. Interaction of carboxyl-terminal peptides of cytosolic-tail of apactin with PDZ domains of NHERF/EBP50 and PDZK-1/CAP70. Mol Cell Biochem 2007; 302:157-67. [PMID: 17390218 DOI: 10.1007/s11010-007-9437-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2006] [Accepted: 02/28/2007] [Indexed: 11/28/2022]
Abstract
The C-terminal PDZ-binding motifs are required for polarized apical/basolateral localization of many membrane proteins. Ezrin-radixin-moesin (ERM) proteins regulate the organization and function of specific cortical structures in polarized epithelial cells by connecting filamentous (F)-actin to plasma membrane proteins through EBP50. Previous work showed that the membrane phosphoprotein apactin (an 80-kDa type I membrane protein derived from pro-Muclin) is associated with the acinar cell apical actin cytoskeleton and that this association is modulated by changes in the phosphorylation state of the apactin cytosolic tail. The carboxyl-terminal amino acids of apactin (-STKL-COOH) are predicted to form a type I PDZ-binding domain, similar to that of CFTR (-DTRL-COOH). Pairwise sequence comparison between NHERF/EBP50 and PDZK1/CAP70 PDZ domains reveals significant identity among the 83 amino-acid residues (12-92) of EBP50 and CAP70 (241-323), which are involved in the interaction with the carboxyl-terminal peptides (STKL-COOH and phosphomimetics) of apactin. Hence, the specificity and affinity of interactions are identical between them, which is corroborated with the two hybrid results. Substitution of all the four-carboxyl-terminal amino acids in the wild type to Ala reduces the interaction. Only the carbonyl oxygen and amide nitrogen of Ala are found to be involved in hydrogen bonding. Further, truncation of the wild carboxyl-terminal peptide to RGQPP-COOH, showed very low affinity of interaction with PDZ1 domain. Only the atom O(epsilon1) of Gln-2 hydrogen bonds with N(epsilon2) of His72 of PDZ domain. Ser-3 amino acid in wild type apactin protein (STKL-COOH) is not involved in hydrogen bonding with PDZ1 domain. However, substitution of Ser-3 to Asp-3 in PDTKL-COOH peptide increases the affinity of interaction of PDTKL-COOH with PDZ1 domain. Thus, carboxyl-terminal Asp(D) -3, Thr(T) -2, Lys(K) -1 and Leu(L) 0 are involved in numerous interactions with PDZ1 domains of NHERF/EBP50 and PDZK1/CAP70.
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Affiliation(s)
- Chanderdeep Tandon
- Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh, 173215, India.
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37
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Abstract
Cell-to-cell communication through gap junctions exists in most animal cells and is essential for many important biological processes including rapid transmission of electric signals to coordinate contraction of cardiac and smooth muscle, the intercellular propagation of Ca(2+) waves and synchronization of physiological processes between adjacent cells within a tissue. Recent studies have shown that connexins (Cx) can have either direct or indirect interactions with other plasma membrane ion channels or membrane transport proteins with important functional consequences. For example, in tissues most severely affected by cystic fibrosis (CF), activation of the CF Transmembrane Conductance Regulator (CFTR) has been shown to influence connexin function. Moreover, a direct interaction between Cx45.6 and the Major Intrinsic Protein/AQP0 in lens appears to influence the process of cell differentiation whereas interactions between aquaporin 4 (AQP4) and Cx43 in mouse astrocytes may coordinate the intercellular movement of ions and water between astrocytes. In this review, we discuss evidence supporting interactions between Cx and membrane channels/transporters including CFTR, aquaporins, ionotropic glutamate receptors, and between pannexin1, another class of putative gap-junction-forming proteins, and Kvbeta3, a regulatory beta-subunit of voltage gated potassium channels. Although the precise molecular nature of these interactions has yet to be defined, their consequences may be critical for normal tissue homeostasis.
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Affiliation(s)
- Marc Chanson
- Dept. of Pediatrics, Geneva University Hospitals, Geneva, Switzerland
| | - Basilio A. Kotsias
- Instituto de Investigaciones Médicas Alfredo Lanari, Universidad de Buenos Aires, Argentina
| | - Camillo Peracchia
- Dept. of Pharmacology and Physiology, University of Rochester, School of Medicine, Rochester, NY, USA
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38
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Abstract
Mutations in cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-regulated chloride channel, cause cystic fibrosis. To investigate interactions of CFTR in living cells, we measured the diffusion of quantum dot-labeled CFTR molecules by single particle tracking. In multiple cell lines, including airway epithelia, CFTR diffused little in the plasma membrane, generally not moving beyond 100-200 nm. However, CFTR became mobile over micrometer distances after 1) truncations of the carboxy terminus, which contains a C-terminal PDZ (PSD95/Dlg/ZO-1) binding motif; 2) blocking PDZ binding by C-terminal green fluorescent protein fusion; 3) disrupting CFTR association with actin by expression of a mutant EBP50/NHERF1 lacking its ezrin binding domain; or 4) skeletal disruption by latrunculin. CFTR also became mobile when the cytoskeletal adaptor protein binding capacity was saturated by overexpressing CFTR or its C terminus. Our data demonstrate remarkable and previously unrecognized immobilization of CFTR in the plasma membrane and provide direct evidence that C-terminal coupling to the actin skeleton via EBP50/ezrin is responsible for its immobility.
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Affiliation(s)
- Peter M Haggie
- Department of Medicine and Physiology, University of California, San Francisco, San Francisco, CA 94143-0521, USA
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39
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Hernando N, Gisler SM, Pribanic S, Déliot N, Capuano P, Wagner CA, Moe OW, Biber J, Murer H. NaPi-IIa and interacting partners. J Physiol 2005; 567:21-6. [PMID: 15890704 PMCID: PMC1474164 DOI: 10.1113/jphysiol.2005.087049] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Accepted: 05/09/2005] [Indexed: 11/08/2022] Open
Abstract
Regulation of renal proximal tubular reabsorption of phosphate (Pi) is one of the critical steps in Pi homeostasis. Experimental evidence suggests that this regulation is achieved mainly by controlling the apical expression of the Na+-dependent Pi cotransporter type IIa (NaPi-IIa) in proximal tubules. Only recently have we started to obtain information regarding the molecular mechanisms that control the apical expression of NaPi-IIa. The first critical observation was the finding that truncation of only its last three amino acid residues has a strong effect on apical expression. A second major finding was the observation that the last intracellular loop of NaPi-IIa contains sequence information that confers parathyroid hormone (PTH) sensitivity. The use of the above domains of the cotransporter in yeast two-hybrid (Y2H) screening allowed the identification of proteins interacting with NaPi-IIa. Biochemical and morphological, as well as functional, analyses have allowed us to obtain insights into the physiological roles of such interactions, although our present knowledge is still far from complete.
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Affiliation(s)
- N Hernando
- Institute of Physiology, Zurich University, CH-8057, Zurich, Switzerland .
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40
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Abstract
Cystic fibrosis (CF) is a genetic disease caused by autosomal recessive mutations of the CF transmembrane regulator, CFTR. CFTR functions in the plasma membrane of epithelial cells lining the lung, pancreas, liver, intestines, sweat duct, and the epididymis. The primary problem in CF is that mutations in CFTR affect its ability to be made, processed, and trafficked to the plasma membrane and/or its function as a Cl(-) channel and conductance regulator. Many proteins and processes normally interact with normal CFTR throughout its life cycle and mutant CFTR during the disease process. Understanding the function of these proteins and processes is expected to provide a clearer understanding of how normal CFTR is involved in salt movement and how mutant CFTR is handled by the cell and leads to the pathophysiology of CF. Recently, efforts to find therapies that correct defective CFTR have been intensifying. To facilitate our understanding of normal and mutant CFTR and the identification of new drug targets for developing novel therapies, a panel of experts was convened by the National Heart, Lung, and Blood Institute to explore the critical questions, challenges, and current opportunities to highlight new areas of research that would facilitate a integrated understanding of the processes and proteins that impact CFTR. The meeting highlighted the multiple pathways and interacting proteins involved in CFTR folding and biosynthesis, processing, and trafficking. A number of critical areas for future study were identified. Although these therapies are promising, a big question remains as to whether simply correcting defective CFTR will lead to significant improvement in patient health or whether the symptoms manifested in CF will require therapies in addition to those that target defective CFTR specifically.
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Affiliation(s)
- William B Guggino
- Department of Physiology and Pediatrics, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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41
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Raghuram V, Hormuth H, Foskett JK. A kinase-regulated mechanism controls CFTR channel gating by disrupting bivalent PDZ domain interactions. Proc Natl Acad Sci U S A 2003; 100:9620-5. [PMID: 12881487 PMCID: PMC170967 DOI: 10.1073/pnas.1633250100] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2003] [Accepted: 06/19/2003] [Indexed: 11/18/2022] Open
Abstract
Dynamic regulation of ion channels is critical for maintaining fluid balance in epithelial tissues. Cystic fibrosis, a genetic disease characterized by impaired fluid transport in epithelial tissues, is caused by dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel activity. Recent studies have shown that binding of PSD-95/Dlg/ZO-1 (PDZ) domain proteins to CFTR is important for retaining it at the apical membrane and for regulating its channel activity. Here, we describe a phosphorylation mechanism that regulates CFTR channel activity, which is mediated by PDZ domains. The Na+/H+ exchanger regulatory factor (NHERF) binds to CFTR and increases its open probability (Po). Protein kinase C disrupts the stimulatory effect of NHERF on CFTR channel Po. Phosphorylation by PKC of Ser-162 in the PDZ2 domain of NHERF is critical for this functional effect. Furthermore, a mutation in PDZ2 that mimics phosphorylation decreases CFTR binding and disrupts the ability of NHERF PDZ1-2 to stimulate CFTR channel Po. Our results identify a role for PKC and suggest that phosphorylation of NHERF PDZ2 domain may be an important mechanism for regulating CFTR channel activity.
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Affiliation(s)
- Viswanathan Raghuram
- Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104-6085, USA
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42
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Nielsen PA, Baruch A, Shestopalov VI, Giepmans BNG, Dunia I, Benedetti EL, Kumar NM. Lens connexins alpha3Cx46 and alpha8Cx50 interact with zonula occludens protein-1 (ZO-1). Mol Biol Cell 2003; 14:2470-81. [PMID: 12808044 PMCID: PMC194895 DOI: 10.1091/mbc.e02-10-0637] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Connexin alpha1Cx43 has previously been shown to bind to the PDZ domain-containing protein ZO-1. The similarity of the carboxyl termini of this connexin and the lens fiber connexins alpha3Cx46 and alpha8Cx50 suggested that these connexins may also interact with ZO-1. ZO-1 was shown to be highly expressed in mouse lenses. Colocalization of ZO-1 with alpha3Cx46 and alpha8Cx50 connexins in fiber cells was demonstrated by immunofluorescence and by fracture-labeling electron microscopy but showed regional variations throughout the lens. ZO-1 was found to coimmunoprecipitate with alpha3Cx46 and alpha8Cx50, and pull-down experiments showed that the second PDZ domain of ZO-1 was involved in this interaction. Transiently expressed alpha3Cx46 and alpha8Cx50 connexins lacking the COOH-terminal residues did not bind to the second PDZ domain but still formed structures resembling gap junctions by immunofluorescence. These results indicate that ZO-1 interacts with lens fiber connexins alpha3Cx46 and alpha8Cx50 in a manner similar to that previously described for alpha1Cx43. The spatial variation in the interaction of ZO-1 with lens gap junctions is intriguing and is suggestive of multiple dynamic roles for this association.
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Affiliation(s)
- Peter A Nielsen
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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43
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Gormley K, Dong Y, Sagnella GA. Regulation of the epithelial sodium channel by accessory proteins. Biochem J 2003; 371:1-14. [PMID: 12460120 PMCID: PMC1223251 DOI: 10.1042/bj20021375] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2002] [Revised: 11/27/2002] [Accepted: 12/03/2002] [Indexed: 11/17/2022]
Abstract
The epithelial sodium channel (ENaC) is of fundamental importance in the control of sodium fluxes in epithelial cells. Modulation of sodium reabsorption through the distal nephron ENaC is an important component in the overall control of sodium balance, blood volume and thereby of blood pressure. This is clearly demonstrated by rare genetic disorders of sodium-channel activity (Liddle's syndrome and pseudohypoaldosteronism type 1), associated with contrasting effects on blood pressure. The mineralocorticoid aldosterone is a well-established modulator of sodium-channel activity. Considerable insight has now been gained into the intracellular signalling pathways linking aldosterone-mediated changes in gene transcription with changes in ion transport. Activating pathways include aldosterone-induced proteins and especially the serum- and glucocorticoid-inducible kinase (SGK) and the small G-protein, K-Ras 2A. Targeting of the ENaC for endocytosis and degradation is now emerging as a major mechanism for the down-regulation of channel activity. Several proteins acting in concert are an intrinsic part of this process but Nedd4 (neural precursor cell expressed developmentally down-regulated 4) is of central importance. Other mechanisms known to interact with ENaC and affect sodium transport include channel-activating protease 1 (CAP-1), a membrane-anchored protein, and the cystic fibrosis transmembrane regulator. The implications of research on accessory factors controlling ENaC activity are wide-ranging. Understanding cellular mechanisms controlling ENaC activity may provide a more detailed insight not only of ion-channel abnormalities in cystic fibrosis but also of the link between abnormal renal sodium transport and essential hypertension.
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Affiliation(s)
- Kelly Gormley
- Division of Neurosciences, St. George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK
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Ostedgaard LS, Randak C, Rokhlina T, Karp P, Vermeer D, Ashbourne Excoffon KJ, Welsh MJ. Effects of C-terminal deletions on cystic fibrosis transmembrane conductance regulator function in cystic fibrosis airway epithelia. Proc Natl Acad Sci U S A 2003; 100:1937-42. [PMID: 12578973 PMCID: PMC149937 DOI: 10.1073/pnas.2627982100] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/30/2002] [Indexed: 11/18/2022] Open
Abstract
To better understand the function of the conserved C terminus of the cystic fibrosis (CF) transmembrane conductance regulator, we studied constructs containing deletions in the C-terminal tail. When expressed in well differentiated CF airway epithelia, each construct localized predominantly to the apical membrane and generated transepithelial Cl(-) current. The results suggested that neither the C-terminal PSD-95/Discs-large/ZO-1 (PDZ)-interacting motif nor other C-terminal sequences were absolutely required for apical expression in airway epithelia. Surprisingly, deleting an acidic cluster near the C terminus reduced both channel opening rate and transepithelial Cl(-) transport, indicating that it influences channel gating. These results may help explain the relative paucity of CF-associated mutations in the C terminus.
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Affiliation(s)
- Lynda S Ostedgaard
- Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA
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Naren AP, Cobb B, Li C, Roy K, Nelson D, Heda GD, Liao J, Kirk KL, Sorscher EJ, Hanrahan J, Clancy JP. A macromolecular complex of beta 2 adrenergic receptor, CFTR, and ezrin/radixin/moesin-binding phosphoprotein 50 is regulated by PKA. Proc Natl Acad Sci U S A 2003; 100:342-6. [PMID: 12502786 PMCID: PMC140971 DOI: 10.1073/pnas.0135434100] [Citation(s) in RCA: 180] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2002] [Indexed: 11/18/2022] Open
Abstract
It has been demonstrated previously that both the cystic fibrosis transmembrane conductance regulator (CFTR) and beta(2) adrenergic receptor (beta(2)AR) can bind ezrinradixinmoesin-binding phosphoprotein 50 (EBP50, also referred to as NHERF) through their PDZ motifs. Here, we show that beta(2) is the major adrenergic receptor isoform expressed in airway epithelia and that it colocalizes with CFTR at the apical membrane. beta(2)AR stimulation increases CFTR activity, in airway epithelial cells, that is glybenclamide sensitive. Deletion of the PDZ motif from CFTR uncouples the channel from the receptor both physically and functionally. This uncoupling is specific to the beta(2)AR receptor and does not affect CFTR coupling to other receptors (e.g., adenosine receptor pathway). Biochemical studies demonstrate the existence of a macromolecular complex involving CFTR-EBP50-beta(2)AR through PDZ-based interactions. Assembly of the complex is regulated by PKA-dependent phosphorylation. Deleting the regulatory domain of CFTR abolishes PKA regulation of complex assembly. This report summarizes a macromolecular signaling complex involving CFTR, the implications of which may be relevant to CFTR-dysfunction diseases.
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Affiliation(s)
- Anjaparavanda P Naren
- Department of Physiology and Biophysics, Medical Center, University of Tennessee Health Science Center, Memphis 38163, USA.
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Abstract
Na+/H+ exchanger regulatory factors, NHERF1 and NHERF2, are structurally related proteins and highly expressed in epithelial cells. These proteins are initially identified as accessory proteins in the regulation of Na+/H+ exchanger isoform 3, NHE3. In addition to regulation of NHE3, recent studies demonstrate the importance of NHERF1 and NHERF2 in recycling and localization of membrane receptors, ion channels and transporters. Recent studies show that serum- and glucocorticoid-induced kinase 1 (SGK1) specifically interacts with NHERF2 but not with NHERF1, adding to the growing number of differences between the two proteins. The association of SGK1 with NHERF2 is necessary for stimulation of NHE3 activity by glucocorticoids. In addition, SGK1 together with NHERF2 stimulates the K+ channel ROMK1, suggesting a broader role of SGK1 in regulation of ion transport.
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Affiliation(s)
- C Chris Yun
- Division of Digestive Disease, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
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Hernando N, Déliot N, Gisler SM, Lederer E, Weinman EJ, Biber J, Murer H. PDZ-domain interactions and apical expression of type IIa Na/P(i) cotransporters. Proc Natl Acad Sci U S A 2002; 99:11957-62. [PMID: 12192091 PMCID: PMC129376 DOI: 10.1073/pnas.182412699] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2002] [Accepted: 07/09/2002] [Indexed: 11/18/2022] Open
Abstract
Type IIa Na/P(i) cotransporters are expressed in renal proximal brush border and are the major determinants of inorganic phosphate (P(i)) reabsorption. Their carboxyl-terminal tail contains information for apical expression, and interacts by means of its three terminal amino acids with several PSD95/DglA/ZO-1-like domain (PDZ)-containing proteins. Two of these proteins, NaPi-Cap1 and Na/H exchanger-regulatory factor 1 (NHERF1), colocalize with the cotransporter in the proximal brush border. We used opossum kidney cells to test the hypothesis of a potential role of PDZ-interactions on the apical expression of the cotransporter. We found that opossum kidney cells contain NaPi-Cap1 and NHERF1 mRNAs. For NHERF1, an apical location of the protein could be documented; this location probably reflects interaction with the cytoskeleton by means of the MERM-binding domain. Overexpression of PDZ domains involved in interaction with the cotransporter (PDZ-1/NHERF1 and PDZ-3/NaPi-Cap1) had a dominant-negative effect, disturbing the apical expression of the cotransporter without affecting the actin cytoskeleton or the basolateral expression of Na/K-ATPase. These data suggest an involvement of PDZ-interactions on the apical expression of type IIa cotransporters.
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Affiliation(s)
- Nati Hernando
- Institute of Physiology, University of Zurich, Wintherthurerstrasse 190, CH-8057 Zurich, Switzerland
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Shenolikar S, Voltz JW, Minkoff CM, Wade JB, Weinman EJ. Targeted disruption of the mouse NHERF-1 gene promotes internalization of proximal tubule sodium-phosphate cotransporter type IIa and renal phosphate wasting. Proc Natl Acad Sci U S A 2002; 99:11470-5. [PMID: 12169661 PMCID: PMC123280 DOI: 10.1073/pnas.162232699] [Citation(s) in RCA: 277] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2002] [Indexed: 11/18/2022] Open
Abstract
Na+/H+ exchanger regulatory factor (NHERF)-1 and NHERF-2, two structurally related protein adapters containing tandem PSD-95/Discs large/ZO-1 (PDZ) domains, were identified as essential factors for protein kinase A-mediated inhibition of the sodium-hydrogen exchanger, NHE3. NHERF-1 and NHERF-2 also bound other cellular targets including the sodium-phosphate cotransporter type IIa encoded by the NPT2 gene. Targeted disruption of the mouse NHERF-1 gene eliminated NHERF-1 expression in kidney and other tissues of the mutant mice without altering NHERF-2 levels in these tissues. NHERF-1 (+/-) and (-/-) male mice maintained normal blood electrolytes but showed increased urinary excretion of phosphate when compared with wild-type (+/+) animals. Although the overall levels of renal NHERF-1 targets, NHE3 and Npt2, were unchanged in the mutant mice, immunocytochemistry showed that the Npt2 protein was aberrantly localized at internal sites in the renal proximal tubule cells. The mislocalization of Npt2 paralleled a reduction in the transporter protein in renal brush-border membranes isolated from the mutant mice. In contrast, NHE3 was appropriately localized at the apical surface of proximal tubules in both wild-type and mutant mice. These data suggested that NHERF-1 played a unique role in the apical targeting and/or trafficking of Npt2 in the mammalian kidney, a function not shared by NHERF-2 or other renal PDZ proteins. Phosphate wasting seen in the NHERF-1(-/-) null mice provided a new experimental system for defining the role of PDZ adapters in the hormonal control of ion transport and renal disease.
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Affiliation(s)
- S Shenolikar
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
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Chen JM, Cutler C, Jacques C, Boeuf G, Denamur E, Lecointre G, Mercier B, Cramb G, Férec C. A combined analysis of the cystic fibrosis transmembrane conductance regulator: implications for structure and disease models. Mol Biol Evol 2001; 18:1771-88. [PMID: 11504857 DOI: 10.1093/oxfordjournals.molbev.a003965] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Over the past decade, nearly 1,000 variants have been identified in the cystic fibrosis transmembrane conductance regulator (CFTR) gene in classic and atypical cystic fibrosis (CF) patients worldwide, and an enormous wealth of information concerning the structure and function of the protein has also been accumulated. These data, if evaluated together in a sequence comparison of all currently available CFTR homologs, are likely to refine the global structure-function relationship of the protein, which will, in turn, facilitate interpretation of the identified mutations in the gene. Based on such a combined analysis, we had recently defined a "functional R domain" of the CFTR protein. First, presenting two full-length cDNA sequences (termed sCFTR-I and sCFTR-II) from the Atlantic salmon (Salmo salar) and an additional partial coding sequence from the eastern gray kangaroo (Macropus giganteus), this study went further to refine the boundaries of the two nucleotide-binding domains (NBDs) and the COOH-terminal tail (C-tail), wherein NBD1 was defined as going from P439 to G646, NBD2 as going from A1225 to E1417, and the C-tail as going from E1418 to L1480. This approach also provided further insights into the differential roles of the two halves of CFTR and highlighted several well-conserved motifs that may be involved in inter- or intramolecular interactions. Moreover, a serious concern that a certain fraction of missense mutations identified in the CFTR gene may not have functional consequences was raised. Finally, phylogenetic analysis of all the full-length CFTR amino acid sequences and an extended set of exon 13--coding nucleotide sequences reinforced the idea that the rabbit may represent a better CF model than the mouse and strengthened the assertion that a long-branch attraction artifact separates the murine rodents from the rabbit and the guinea pig, the other Glires.
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Affiliation(s)
- J M Chen
- Institut National de la Santé et de la Recherche Médicale EMI 01 15, Etablissement Français du Sang-Bretagne, Universite de Bretagne Occidentale, and Centre Hospitalier Universitaire, Brest, France
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Benharouga M, Haardt M, Kartner N, Lukacs GL. COOH-terminal truncations promote proteasome-dependent degradation of mature cystic fibrosis transmembrane conductance regulator from post-Golgi compartments. J Cell Biol 2001; 153:957-70. [PMID: 11381082 PMCID: PMC2174331 DOI: 10.1083/jcb.153.5.957] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Impaired biosynthetic processing of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR), a cAMP-regulated chloride channel, constitutes the most common cause of CF. Recently, we have identified a distinct category of mutation, caused by premature stop codons and frameshift mutations, which manifests in diminished expression of COOH-terminally truncated CFTR at the cell surface. Although the biosynthetic processing and plasma membrane targeting of truncated CFTRs are preserved, the turnover of the complex-glycosylated mutant is sixfold faster than its wild-type (wt) counterpart. Destabilization of the truncated CFTR coincides with its enhanced susceptibility to proteasome-dependent degradation from post-Golgi compartments globally, and the plasma membrane specifically, determined by pulse-chase analysis in conjunction with cell surface biotinylation. Proteolytic cleavage of the full-length complex-glycosylated wt and degradation intermediates derived from both T70 and wt CFTR requires endolysosomal proteases. The enhanced protease sensitivity in vitro and the decreased thermostability of the complex-glycosylated T70 CFTR in vivo suggest that structural destabilization may account for the increased proteasome susceptibility and the short residence time at the cell surface. These in turn are responsible, at least in part, for the phenotypic manifestation of CF. We propose that the proteasome-ubiquitin pathway may be involved in the peripheral quality control of other, partially unfolded membrane proteins as well.
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Affiliation(s)
- Mohamed Benharouga
- Program in Lung and Cell Biology, The Hospital for Sick Children, Toronto M5G 1X8, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto M5G 1X8, Ontario, Canada
| | - Martin Haardt
- Program in Lung and Cell Biology, The Hospital for Sick Children, Toronto M5G 1X8, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto M5G 1X8, Ontario, Canada
| | - Norbert Kartner
- Department of Pharmacology, University of Toronto, Toronto M5G 1X8, Ontario, Canada
| | - Gergely L. Lukacs
- Program in Lung and Cell Biology, The Hospital for Sick Children, Toronto M5G 1X8, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto M5G 1X8, Ontario, Canada
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