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Mondini A, Sassone F, Civello DA, Garavaglia ML, Bazzini C, Rodighiero S, Vezzoli V, Conti F, Torielli L, Capasso G, Paulmichl M, Meyer G. Hypertension-linked mutation of α-adducin increases CFTR surface expression and activity in HEK and cultured rat distal convoluted tubule cells. PLoS One 2012; 7:e52014. [PMID: 23284854 PMCID: PMC3528715 DOI: 10.1371/journal.pone.0052014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 11/08/2012] [Indexed: 11/18/2022] Open
Abstract
The CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) activity and localization are influenced by the cytoskeleton, in particular by actin and its polymerization state. In this study we investigated whether the expression of the hypertensive mutations of α-adducin (G460W-S586C in humans, F316Y in rats), an actin capping protein, led to a functional modification of CFTR activity and surface expression. The experiments were performed on HEK293 T cells cotransfected with CFTR and the human wild type (WT) or G460W mutated α-adducin. In whole-cell patch-clamp experiments, both the CFTR chloride current and the slope of current activation after forskolin addition were significantly higher in HEK cells overexpressing the G460W adducin. A higher plasma membrane density of active CFTR channels was confirmed by cell-attached patch-clamp experiments, both in HEK cells and in cultured primary DCT cells, isolated from MHS (Milan Hypertensive Strain, a Wistar rat (Rattus norvegicus) hypertensive model carrying the F316Y adducin mutation), compared to MNS (Milan Normotensive Strain) rats. Western blot experiments demonstrated an increase of the plasma membrane CFTR protein expression, with a modification of the channel glycosylation state, in the presence of the mutated adducin. A higher retention of CFTR protein in the plasma membrane was confirmed both by FRAP (Fluorescence Recovery After Photobleaching) and photoactivation experiments. The present data indicate that in HEK cells and in isolated DCT cells the presence of the G460W-S586C hypertensive variant of adducin increases CFTR channel activity, possibly by altering its membrane turnover and inducing a retention of the channel in the plasmamembrane. Since CFTR is known to modulate the activity of many others transport systems, the increased surface expression of the channel could have consequences on the whole network of transport in kidney cells.
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Affiliation(s)
- Anna Mondini
- Department of Life Sciences, Università degli Studi di Milano, Milano, Italy
| | - Francesca Sassone
- Department of Life Sciences, Università degli Studi di Milano, Milano, Italy
| | | | | | - Claudia Bazzini
- Department of Life Sciences, Università degli Studi di Milano, Milano, Italy
| | | | - Valeria Vezzoli
- Department of Life Sciences, Università degli Studi di Milano, Milano, Italy
| | - Fabio Conti
- Prassis Research Institute, Sigma Tau, Settimo M.se, Italy
| | - Lucia Torielli
- Prassis Research Institute, Sigma Tau, Settimo M.se, Italy
| | | | - Markus Paulmichl
- Institut of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | - Giuliano Meyer
- Department of Life Sciences, Università degli Studi di Milano, Milano, Italy
- * E-mail:
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Lange T, Jungmann P, Haberle J, Falk S, Duebbers A, Bruns R, Ebner A, Hinterdorfer P, Oberleithner H, Schillers H. Reduced number of CFTR molecules in erythrocyte plasma membrane of cystic fibrosis patients. Mol Membr Biol 2009; 23:317-23. [PMID: 16923725 DOI: 10.1080/09687860600738304] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Cystic fibrosis (CF), the most common genetic disease among Caucasians, is caused by mutations in the gene encoding CFTR (cystic fibrosis transmembrane conductance regulator). The most frequent mutation, DeltaF508, results in protein misfolding and, as a consequence, prevents CFTR from reaching its final location at the cell surface. CFTR is expressed in various cell types including red blood cells. The functional role of CFTR in erythrocytes is still unclear. Since the number of CFTR copies in a single erythrocyte of healthy donors and CF patients with a homozygous DeltaF508 mutation is unknown, we counted CFTR, localized in erythrocyte plasma membrane, at the single molecule level. A novel experimental approach combining atomic force microscopy with quantum-dot-labeled anti-CFTR antibodies, used as topographic surface markers, was employed to detect individual CFTR molecules. Analysis of erythrocyte plasma membranes taken from healthy donors and CF patients with a homozygous DeltaF508 mutation reveals mean (SEM) values of 698 (12.8) (n=542) and 172 (3.8) (n=538) CFTR molecules per red blood cell, respectively. We conclude that erythrocytes reflect the CFTR status of the organism and that quantification of CFTR in a blood sample could be useful in the diagnosis of CFTR related diseases.
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Affiliation(s)
- Tobias Lange
- Institute of Physiology II, University of Muenster, and Department of Pediatrics, University Hospitals of Muenster, Germany
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Souza-Menezes J, Morales MM. CFTR structure and function: is there a role in the kidney? Biophys Rev 2009; 1:3-12. [PMID: 28510151 PMCID: PMC5387792 DOI: 10.1007/s12551-008-0002-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Accepted: 12/19/2008] [Indexed: 12/27/2022] Open
Abstract
Cystic fibrosis (CF) is a lethal autosomal recessive genetic disease caused by mutations in the CF transmembrane conductance regulator (CFTR). Mutations in the CFTR gene may result in a defective protein processing that leads to changes in function and regulation of this chloride channel. Despite of the expression of CFTR in the kidney, patients with CF do not present major renal dysfunction, but it is known that both the urinary excretion of proteins and renal capacity to concentrate and dilute urine are altered in these patients. CFTR mRNA is expressed in all nephron segments of rat and human, and this abundance is more prominent in renal cortex and outer medulla renal areas. CFTR protein was detected in apical surface of both proximal and distal tubules of rat kidney but not in the outer medullary collecting ducts. Studies have demonstrated that CFTR does not only transport Cl- but also ATP. ATP transport by CFTR could be involved in the control of other ion transporters such as Na+ (ENaC) and K+ (renal outer medullary potassium) channels, especially in TAL and CCD. In the kidney, CFTR also might be involved in the endocytosis of low-molecular-weight proteins by proximal tubules. This review is focused on the CFTR function and structure, its role in the renal physiology, and its modulation by hormones involved in the control of extracellular fluid volume.
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Affiliation(s)
- J. Souza-Menezes
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Macaé, Brazil
| | - M. M. Morales
- Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Av Carlos Chagas Filho 373, Centro de Ciências da Saúde Bloco G Sala 48, Cidade Universitária, Rio de Janeiro, 21941-902 Brazil
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Ebner A, Nikova D, Lange T, Häberle J, Falk S, Dübbers A, Bruns R, Hinterdorfer P, Oberleithner H, Schillers H. Determination of CFTR densities in erythrocyte plasma membranes using recognition imaging. NANOTECHNOLOGY 2008; 19:384017. [PMID: 21832576 DOI: 10.1088/0957-4484/19/38/384017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
CFTR (cystic fibrosis transmembrane conductance regulator) is a cAMP-regulated chloride (Cl(-)) channel that plays an important role in salt and fluid movement across epithelia. Cystic fibrosis (CF), the most common genetic disease among Caucasians, is caused by mutations in the gene encoding CFTR. The most predominant mutation, F508del, disturbs CFTR protein trafficking, resulting in a reduced number of CFTR in the plasma membrane. Recent studies indicate that CFTR is not only found in epithelia but also in human erythrocytes. Although considerable attempts have been made to quantify CFTR in cells, conclusions on numbers of CFTR molecules localized in the plasma membrane have been drawn indirectly. AFM has the power to provide the needed information, since both sub-molecular spatial resolution and direct protein recognition via antibody-antigen interaction can be observed. We performed a quantification study of the CFTR copies in erythrocyte membranes at the single molecule level, and compared the difference between healthy donors and CF patients. We detected that the number of CFTR molecules is reduced by 70% in erythrocytes of cystic fibrosis patients.
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Affiliation(s)
- Andreas Ebner
- Institute for Biophysics, University of Linz, A-4040 Linz, Austria
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Current World Literature. Curr Opin Nephrol Hypertens 2005. [DOI: 10.1097/01.mnh.0000172731.05865.69] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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