scholarly journals Sorting Nexin 27 (SNX27): A Novel Regulator of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Trafficking

2018 ◽  
Author(s):  
Mark I. McDermott ◽  
William R. Thelin ◽  
Yun Chen ◽  
Patrick T. Lyons ◽  
Gabrielle Reilly ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Plasma Membrane ◽  
Cell Surface ◽  
Pdz Domain ◽  
Type I ◽  
Apical Surface ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Sorting Nexin ◽  
Cystic Fibrosis Transmembrane

AbstractThe underlying defect in cystic fibrosis is mutation of the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated chloride channel expressed at the apical surface of lung epithelia. In addition to its export and maintenance at the cell surface, CFTR regulation involves repeated cycles of transport through the endosomal trafficking system, including endocytosis and recycling. Many of the known disease mutations cause CFTR intracellular trafficking defects that result in failure of ion channel delivery to the apical plasma membrane. Corrective maneuvers directed at improving transport to the plasma membrane are thwarted by rapid internalization and degradation of the mutant CFTR proteins. The molecular mechanisms involved in these processes are not completely understood but may involve protein-protein interactions with the C-terminal type I PDZ-binding motif of CFTR. Using a proteomic approach, we identify sorting nexin 27 (SNX27) as a novel CFTR binding partner in human airway epithelial Calu-3 cells. SNX27 and CFTR interact directly, with the SNX27 PDZ domain being both necessary and sufficient for this interaction. SNX27 co-localizes with internalized CFTR at sub-apical endosomal sites in polarized Calu-3 cells, and either knockdown of the endogenous SNX27, or over-expression of a dominant-negative SNX27 mutant, resulted in significant decreases in cell surface CFTR levels. CFTR internalization was not affected by SNX27 knockdown, but defects were observed in the recycling arm of CFTR trafficking through the endosomal system. Furthermore, knockdown of SNX27 in Calu-3 cells resulted in significant decreases in CFTR protein levels, consistent with degradation of the internalized pool. These data identify SNX27 as a physiologically significant regulator of CFTR trafficking and homeostasis in epithelial cells.

scholarly journals Constitutive internalization of cystic fibrosis transmembrane conductance regulator occurs via clathrin-dependent endocytosis and is regulated by protein phosphorylation

1997 ◽  
Vol 328 (2) ◽  
pp. 353-361 ◽  
Author(s):  
L. Gergely LUKACS ◽  
Gersana SEGAL ◽  
Norbert KARTNER ◽  
Sergio GRINSTEIN ◽  
Fred ZHANG
Keyword(s):  
Cystic Fibrosis ◽  
Plasma Membrane ◽  
Protein Kinase ◽  
Cell Surface ◽  
Protein Phosphorylation ◽  
Chinese Hamster ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Hypertonic Medium ◽  
Cystic Fibrosis Transmembrane

Although the cystic fibrosis transmembrane conductance regulator (CFTR) is primarily implicated in the regulation of plasma-membrane chloride permeability, immunolocalization and functional studies indicate the presence of CFTR in the endosomal compartment. The mechanism of CFTR delivery from the cell surface to endosomes is not understood. To delineate the internalization pathway, both the rate and extent of CFTR accumulation in endosomes were monitored in stably transfected Chinese hamster ovary (CHO) cells. The role of clathrin-dependent endocytosis was assessed in cells exposed to hypertonic medium, potassium depletion or intracellular acid-load. These treatments inhibited clathrin-dependent endocytosis by > 90%, as verified by measurements of 125I-transferrin uptake. Functional association of CFTR with newly formed endosomes was determined by an endosomal pH dissipation protocol [Lukacs, Chang, Kartner, Rotstein, Riordan and Grinstein (1992) J. Biol. Chem. 267, 14568-14572]. As a second approach, endocytosis of CFTR was determined after cell-surface biotinylation with the cleavable sulphosuccinimidyl-2-(biotinamido)ethyl-1,3-dithiopropionate. Both the biochemical and the functional assays indicated that arresting the formation of clathrin-coated vesicles inhibited the retrieval of the CFTR from the plasma membrane to endosomes. An overall arrest of membrane traffic cannot account for the inhibition of CFTR internalization, since the fluid-phase endocytosis was not effected by the treatments used. Thus the efficient, constitutive internalization of surface CFTR (5% per min) occurs, predominantly by clathrin-dependent endocytosis. Stimulation of protein phosphorylation by cAMP-dependent protein kinase A and by protein kinase C decreased the rate of internalization of cell-surface biotinylated CFTR, and contributed to a substantial diminution of the internal CFTR pool compared with that of unstimulated cells. These results suggest that the rate of CFTR internalization may participate in the determination of the CFTR channel density, and consequently, of the cAMP-stimulated chloride conductance of the plasma membrane.

Rme-1 regulates the recycling of the cystic fibrosis transmembrane conductance regulator

2003 ◽  
Vol 285 (5) ◽  
pp. C1009-C1018 ◽  
Author(s):  
John A. Picciano ◽  
Nadia Ameen ◽  
Barth D. Grant ◽  
Neil A. Bradbury
Keyword(s):  
Cystic Fibrosis ◽  
Plasma Membrane ◽  
Cell Surface ◽  
Dominant Negative ◽  
Traffic Information ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Endosomal Recycling ◽  
Carboxyl Terminal ◽  
Cystic Fibrosis Transmembrane

Endocytic motifs in the carboxyl terminus of cystic fibrosis transmembrane conductance regulator (CFTR) direct internalization from the plasma membrane by clathrin-mediated endocytosis. However, the fate of such internalized CFTR has remained unknown. Internalized membrane proteins can be either targeted for degradation or recycled back to the plasma membrane. Using cell surface biotinylation and antibody uptake studies, we show that CFTR undergoes constitutive endocytosis and recycling back to the plasma membrane. Expression of dominant negative Rme-1 (a protein that regulates exit from the endosomal recycling compartment) in CFTR-expressing cells results in the expansion of recycling compartments. Transferrin, a marker for the endosomal recycling compartment, and CFTR accumulate in these enlarged recycling endosomes. Such accumulation leads to a loss of cell surface CFTR because it is prevented from being recycled back to the cell surface. In contrast, traffic of the low-density lipoprotein (LDL) is unaffected by the expression of dominant negative Rme-1. In addition, chimeras containing the extracellular domain of the transferrin receptor and the carboxyl terminal tail of CFTR also enter Rme-1-regulated recycling compartments and accumulate in these compartments containing dominant negative Rme-1, suggesting that in addition to endocytic signals, the carboxyl terminal tail of CFTR also contains intracellular traffic information.

scholarly journals Functional expression and apical localization of the cystic fibrosis transmembrane conductance regulator in MDCK I cells

1997 ◽  
Vol 322 (1) ◽  
pp. 259-265 ◽  
Author(s):  
Abdalla MOHAMED ◽  
Donald FERGUSON ◽  
Fabian S. SEIBERT ◽  
Hou-ming CAI ◽  
Norbert KARTNER ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Plasma Membrane ◽  
Proximal Tubule ◽  
Model Systems ◽  
Type I ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Cystic Fibrosis Transmembrane ◽  
I Cells ◽  
Mdck I

The gene product affected in cystic fibrosis, the cystic fibrosis transmembrane conductance regulator (CFTR), is a chloride-selective ion channel that is regulated by cAMP-dependent protein kinase-mediated phosphorylation, ATP binding and ATP hydrolysis. Mutations in the CFTR gene may result in cystic fibrosis characterized by severe pathology (e.g. recurrent pulmonary infection, male infertility and pancreatic insufficiency) involving organs expressing the CFTR. Interestingly, in the kidney, where expression of the CFTR has been reported, impaired ion transport in patients suffering from cystic fibrosis could not be observed. To understand the role of the CFTR in chloride transport in the kidney, we attempted to identify an epithelial cell line that can serve as a model. We demonstrate that the CFTR is expressed constitutively in MadineŐDarby canine kidney (MDCK) type I cells, which are thought to have originated from the distal tubule of the dog nephron. We show expression at the mRNA level, using reverse transcriptase-PCR, and at the protein level, using Western blot analysis with three different monoclonal antibodies. Iodide efflux measurements indicate that CFTR expression confers a plasma membrane anion conductance that is responsive to stimulation by cAMP. The cAMP-stimulated iodide release is sensitive to glybenclamide, diphenylamine carboxylic acid and 5-nitro-2-(3-phenylpropylamino)benzoic acid, but not to 4,4ƀ-di-isothiocyanostilbene-2,2ƀ-disulphonic acid, an inhibitor profile characteristic of the CFTR chloride channel. Finally, the polarized localization of the CFTR to the apical plasma membrane was established by iodide efflux measurements and cell-surface biotinylation on MDCK I monolayers. Interestingly, MDCK type II cells, which are thought to have originated from the proximal tubule of the kidney, lack CFTR protein expression and cAMP-stimulated chloride conductance. In conclusion, we propose that MDCK type I and II cells can serve as convenient model systems to study the physiological role and differential expression of CFTR in the distal and proximal tubule respectively.

Dynasore inhibits removal of wild-type and ΔF508 cystic fibrosis transmembrane conductance regulator (CFTR) from the plasma membrane

2009 ◽  
Vol 421 (3) ◽  
pp. 377-385 ◽  
Author(s):  
Andrew Young ◽  
Martina Gentzsch ◽  
Cynthia Y. Abban ◽  
Ying Jia ◽  
Patricio I. Meneses ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Cell Surface ◽  
Small Molecule ◽  
Short Exposure ◽  
Growth Media ◽  
Transmembrane Conductance Regulator ◽  
Wild Type ◽  
Transmembrane Conductance ◽  
Δf508 Cftr ◽  
Cystic Fibrosis Transmembrane

Dynasore, a small molecule inhibitor of dynamin, was used to probe the role of dynamin in the endocytosis of wild-type and mutant CFTR (cystic fibrosis transmembrane conductance regulator). Internalization of both wild-type and ‘temperature-corrected’ ΔF508 CFTR was markedly inhibited by a short exposure to dynasore, implicating dynamin as a key element in the endocytic internalization of both wild-type and mutant CFTR. The inhibitory effect of dynasore was readily reversible upon washout of dynasore from the growth media. Corr-4 ({2-(5-chloro-2-methoxy-phenylamino)-4′-methyl-[4,5′]-bithiazolyl-2′-yl}-phenyl-methanonone), a pharmacological corrector of ΔF508 CFTR biosynthesis, caused a marked increase in the cell surface expression of mutant CFTR. Co-incubation of ΔF508 CFTR expressing cells with Corr-4 and dynasore caused a significantly greater level of cell surface CFTR than that observed in the presence of Corr-4 alone. These results argue that inhibiting the endocytic internalization of mutant CFTR provides a novel therapeutic target for augmenting the benefits of small molecule correctors of mutant CFTR biosynthesis.

scholarly journals Dimeric cystic fibrosis transmembrane conductance regulator exists in the plasma membrane

2003 ◽  
Vol 374 (3) ◽  
pp. 793-797 ◽  
Author(s):  
Mohabir RAMJEESINGH ◽  
Jackie F. KIDD ◽  
Ling Jun HUAN ◽  
Yanchun WANG ◽  
Christine E. BEAR
Keyword(s):  
Cystic Fibrosis ◽  
Epithelial Cells ◽  
Cell Biology ◽  
Plasma Membranes ◽  
Chinese Hamster Ovary Cells ◽  
Apical Surface ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
The Impact ◽  
Cystic Fibrosis Transmembrane

CFTR (cystic fibrosis transmembrane conductance regulator) mediates chloride conduction across the apical membrane of epithelia, and mutations in CFTR lead to defective epithelial fluid transport. Recently, there has been considerable interest in determining the quaternary structure of CFTR at the cell surface, as such information is a key to understand the molecular basis for pathogenesis in patients harbouring disease-causing mutations. In our previous work [Ramjeesingh, Li, Kogan, Wang, Huan and Bear (2001) Biochemistry 40, 10700–10706], we showed that monomeric CFTR is the minimal functional form of the protein, yet when expressed in Sf 9 cells using the baculovirus system, it also exists as dimers. The purpose of the present study was to determine if dimeric CFTR exists at the surface of mammalian cells, and particularly in epithelial cells. CFTR solubilized from membranes prepared from Chinese-hamster ovary cells stably expressing CFTR and from T84 epithelial cells migrates as predicted for monomeric, dimeric and larger complexes when subjected to sizing by gel filtration and analysis by non-dissociative electrophoresis. Purification of plasma membranes led to the enrichment of CFTR dimers and this structure exists as the complex glycosylated form of the protein, supporting the concept that dimeric CFTR is physiologically relevant. Consistent with its localization in plasma membranes, dimeric CFTR was labelled by surface biotinylation. Furthermore, dimeric CFTR was captured at the apical surface of intact epithelial cells by application of a membrane-impermeable chemical cross-linker. Therefore it follows from the present study that CFTR dimers exist at the surface of epithelial cells. Further studies are necessary to understand the impact of dimerization on the cell biology of wild-type and mutant CFTR proteins.

scholarly journals PDZ Domain Interaction Controls the Endocytic Recycling of the Cystic Fibrosis Transmembrane Conductance Regulator

2002 ◽  
Vol 277 (42) ◽  
pp. 40099-40105 ◽  
Author(s):  
Agnieszka Swiatecka-Urban ◽  
Marc Duhaime ◽  
Bonita Coutermarsh ◽  
Katherine H. Karlson ◽  
James Collawn ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pdz Domain ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Domain Interaction ◽  
Endocytic Recycling ◽  
Cystic Fibrosis Transmembrane
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