Na+-dependent HCO3− uptake into the rat choroid plexus epithelium is partially DIDS sensitive

2005 ◽  
Vol 289 (6) ◽  
pp. C1448-C1456 ◽  
Author(s):  
Elena V. Bouzinova ◽  
Jeppe Praetorius ◽  
Leila V. Virkki ◽  
Søren Nielsen ◽  
Walter F. Boron ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Choroid Plexus ◽  
Brush Border Membrane ◽  
Bicarbonate Transport ◽  
Excitation Wavelength ◽  
Membrane Domain ◽  
Choroid Plexus Epithelium ◽  
Transport Inhibitor ◽  
Acid Loading ◽  
Choroid Plexus Epithelial

Several studies suggest the involvement of Na+ and HCO3− transport in the formation of cerebrospinal fluid. Two Na+-dependent HCO3− transporters were recently localized to the epithelial cells of the rat choroid plexus (NBCn1 and NCBE), and the mRNA for a third protein was also detected (NBCe2) (Praetorius J, Nejsum LN, and Nielsen S. Am J Physiol Cell Physiol 286: C601–C610, 2004). Our goal was to immunolocalize the NBCe2 to the choroid plexus by immunohistochemistry and immunogold electronmicroscopy and to functionally characterize the bicarbonate transport in the isolated rat choroid plexus by measurements of intracellular pH (pHi) using a dual-excitation wavelength pH-sensitive dye (BCECF). Both antisera derived from COOH-terminal and NH2-terminal NBCe2 peptides localized NBCe2 to the brush-border membrane domain of choroid plexus epithelial cells. Steady-state pHi in choroidal cells increased from 7.03 ± 0.02 to 7.38 ± 0.02 ( n = 41) after addition of CO2/HCO3− into the bath solution. This increase was Na+ dependent and inhibited by the Cl− and HCO3− transport inhibitor DIDS (200 μM). This suggests the presence of Na+-dependent, partially DIDS-sensitive HCO3− uptake. The pHi recovery after acid loading revealed an initial Na+ and HCO3−-dependent net base flux of 0.828 ± 0.116 mM/s ( n = 8). The initial flux in the presence of CO2/HCO3− was unaffected by DIDS. Our data support the existence of both DIDS-sensitive and -insensitive Na+- and HCO3−-dependent base loader uptake into the rat choroid plexus epithelial cells. This is consistent with the localization of the three base transporters NBCn1, Na+-driven Cl− bicarbonate exchanger, and NBCe2 in this tissue.

scholarly journals The murine choroid plexus epithelium expresses the 2Cl−/H+ exchanger ClC-7 and Na+/H+ exchanger NHE6 in the luminal membrane domain

2018 ◽  
Vol 314 (4) ◽  
pp. C439-C448 ◽  
Author(s):  
Helle H. Damkier ◽  
Henriette L. Christensen ◽  
Inga B. Christensen ◽  
Qi Wu ◽  
Robert A. Fenton ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Epithelial Cells ◽  
Choroid Plexus ◽  
Intracellular Ph ◽  
Ph Regulation ◽  
Membrane Domain ◽  
Choroid Plexus Epithelium ◽  
Acid Base ◽  
Luminal Membrane ◽  
Choroid Plexus Epithelial

The choroid plexus epithelium within the brain ventricles secretes the majority of the cerebrospinal fluid (CSF). The luminal Na+-K+-ATPase acts in concert with a host of other transport proteins to mediate efficient fluid secretion across the epithelium. The CSF contains little protein buffer, but the pH value seems nonetheless maintained within narrow limits, even when faced with acid-base challenges. The involvement of choroid plexus acid-base transporters in CSF pH regulation is highlighted by the expression of several acid-base transporters in the epithelium. The aim of the present study was to identify novel acid-base transporters expressed in the luminal membrane of the choroid plexus epithelium to pave the way for systematic investigations of each candidate transporter in the regulation of CSF pH. Mass spectrometry analysis of proteins from epithelial cells isolated by fluorescence-activated cell sorting identified the Cl−/H+ exchangers ClC-3, -4, -5, and -7 in addition to known choroid plexus acid-base transporters. RT-PCR on FACS isolated epithelial cells confirmed the expression of the corresponding mRNAs, as well as Na+/H+ exchanger NHE6 mRNA. Both NHE6 and ClC-7 were immunolocalized to the luminal plasma membrane domain of the choroid plexus epithelial cells. Dynamic imaging of intracellular pH and membrane potential changes in isolated choroid plexus epithelial cells demonstrated Cl− gradient-driven changes in intracellular pH and membrane potential that are consistent with Cl−/H+ exchange. In conclusion, we have detected for the first time NHE6 and ClC-7 in the choroid plexus, which are potentially involved in pH regulation of the CSF.

scholarly journals Glucose, Fructose, and Urate Transporters in the Choroid Plexus Epithelium

2020 ◽  
Vol 21 (19) ◽  
pp. 7230
Author(s):  
Yoichi Chiba ◽  
Ryuta Murakami ◽  
Koichi Matsumoto ◽  
Keiji Wakamatsu ◽  
Wakako Nonaka ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Choroid Plexus ◽  
High Energy ◽  
Choroid Plexus Epithelium ◽  
Energy Demands ◽  
Total Brain ◽  
Proximal Tubular ◽  
Renal Proximal Tubular ◽  
And Function ◽  
Choroid Plexus Epithelial

The choroid plexus plays a central role in the regulation of the microenvironment of the central nervous system by secreting the majority of the cerebrospinal fluid and controlling its composition, despite that it only represents approximately 1% of the total brain weight. In addition to a variety of transporter and channel proteins for solutes and water, the choroid plexus epithelial cells are equipped with glucose, fructose, and urate transporters that are used as energy sources or antioxidative neuroprotective substrates. This review focuses on the recent advances in the understanding of the transporters of the SLC2A and SLC5A families (GLUT1, SGLT2, GLUT5, GLUT8, and GLUT9), as well as on the urate-transporting URAT1 and BCRP/ABCG2, which are expressed in choroid plexus epithelial cells. The glucose, fructose, and urate transporters repertoire in the choroid plexus epithelium share similar features with the renal proximal tubular epithelium, although some of these transporters exhibit inversely polarized submembrane localization. Since choroid plexus epithelial cells have high energy demands for proper functioning, a decline in the expression and function of these transporters can contribute to the process of age-associated brain impairment and pathophysiology of neurodegenerative diseases.

scholarly journals Choroid plexus epithelial cells express the adhesion protein P-cadherin at cell-cell contacts and syntaxin-4 in the luminal membrane domain

2018 ◽  
Vol 314 (5) ◽  
pp. C519-C533 ◽  
Author(s):  
Inga Baasch Christensen ◽  
Esben Nees Mogensen ◽  
Helle Hasager Damkier ◽  
Jeppe Praetorius
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Choroid Plexus ◽  
Basolateral Membrane ◽  
Membrane Domain ◽  
Cell Contacts ◽  
Luminal Membrane ◽  
Syntaxin 4 ◽  
Choroid Plexus Epithelial ◽  
Cell Cell

The choroid plexus epithelial cells (CPECs) belong to a small group of polarized cells, where the Na+-K+-ATPase is expressed in the luminal membrane. The basic polarity of the cells is, therefore, still debated. We investigated the subcellular distribution of an array of proteins known to play fundamental roles either in establishing and maintaining basic cell polarity or in the polarized delivery and recycling of plasma membrane proteins. Immunofluorescence histochemical analysis was applied to determine the subcellular localization of apical and basolateral membrane determinants. Mass spectrometry analysis of CPECs isolated by fluorescence-activated cell sorting was applied to determine the expression of specific forms of the proteins. CPECs mainly express the cell-adhesive P-cadherin, which is localized to the lateral membranes. Proteins belonging to the Crumbs and partitioning defective (Par) protein complexes were all localized to the luminal membrane domain. Par-1 and the Scribble complex were localized to the basolateral membrane domain. Lethal(2) giant larvae homolog 2 (Lgl2) labeling was preferentially observed in the luminal membrane domain. Phosphatidylinositol 3,4,5-trisphosphate (PIP3) was immunolocalized to the basolateral membrane domain, while phosphatidylinositol 4,5-bisphosphate (PIP2) staining was most prominent in the luminal membrane domain along with the PIP3 phosphatase, Pten. The apical target-SNARE syntaxin-3 and the basolateral target-SNARE syntaxin-4 were both localized to the apical membrane domain in CPECs, which lack cellular expression of the clathrin adaptor protein AP-1B for basolateral protein recycling. In conclusion, the CPECs are conventionally polarized, but express P-cadherin at cell-cell contacts, and Lgl2 and syntaxin-4 in the luminal plasma membrane domain.

scholarly journals Nhe1 is a luminal Na+/H+ exchanger in mouse choroid plexus and is targeted to the basolateral membrane in Ncbe/Nbcn2-null mice

2009 ◽  
Vol 296 (6) ◽  
pp. C1291-C1300 ◽  
Author(s):  
Helle Hasager Damkier ◽  
Vikram Prasad ◽  
Christian Andreas Hübner ◽  
Jeppe Praetorius
Keyword(s):  
Choroid Plexus ◽  
Basolateral Membrane ◽  
Anion Transport ◽  
Wild Type ◽  
Membrane Domain ◽  
Choroid Plexus Epithelium ◽  
Major Fraction ◽  
Compensatory Response ◽  
Luminal Membrane ◽  
Transport Inhibitor

The choroid plexus epithelium (CPE) secretes the major fraction of the cerebrospinal fluid (CSF). The Na+-HCO3− transporter Ncbe/Nbcn2 in the basolateral membrane of CPE cells is important for Na+-dependent pHi increases and probably for CSF secretion. In the current study, the anion transport inhibitor DIDS had no effect on the residual pHi recovery in acidified CPE from Ncbe/Nbcn2 knockout mouse by 2′,7′- bis(2-carboxyethyl)-5( 6 )-carboxyfluorescein (BCECF)-fluorescence microscopy in the presence of CO2/HCO3− (Ncbe/Nbcn2-ko+DIDS 109% of control, P = 0.76, n = 5). Thus Ncbe/Nbcn2 mediates the DIDS-sensitive Na+-dependent pHi recovery in the CPE. The Na+/H+ exchanger-1 Nhe1 is proposed to mediate similar functions as Ncbe/Nbcn2 in CPE. Here, we immunolocalize the Nhe1 protein to the luminal membrane domain in mouse and human CPE. The Na+-dependent pHi recovery of Nhe1 wild-type (Nhe1-wt) mice in the absence of CO2/HCO3− was abolished in the Nhe1 knockout CPE (Nhe1-ko 0.37% of Nhe1-wt, P = 0.0007, n = 5). In Ncbe/Nbcn2-ko mice, Nhe1 was targeted to the basolateral membrane. Nevertheless, the luminal Na+-dependent pHi recovery was increased in Ncbe/Nbcn2-ko compared with wild-type littermates (Nhe1-ko 146% of Nhe1-wt, P = 0.007, n = 5). Whereas the luminal Nhe activity was inhibited by the Nhe blocker EIPA (10 μM) in the Ncbe/Nbcn2-wt, it was insensitive to the inhibitor in Ncbe/Nbcn2-ko (Ncbe/Nbcn2-ko+EIPA 100% of control, P = 0.98, n = 5). This indicates that a luminal EIPA-insensitive Nhe was induced in Ncbe/Nbcn2-ko CPE and that EIPA-sensitive Nhe activity was basolateral. The Nhe1 translocation in Ncbe/Nbcn2-ko CPE may reflect a compensatory response, which provides the cells with better means of regulating pHi or transporting Na+ after Ncbe/Nbcn2 disruption.

scholarly journals Multiple Na,K-ATPase Subunits Colocalize in the Brush Border of Mouse Choroid Plexus Epithelial Cells

2021 ◽  
Vol 22 (4) ◽  
pp. 1569
Author(s):  
Inga Baasch Christensen ◽  
Lei Cheng ◽  
Jonathan R. Brewer ◽  
Udo Bartsch ◽  
Robert A. Fenton ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Choroid Plexus ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Full Range ◽  
Stimulated Emission ◽  
Actin Binding ◽  
Pcr Analysis ◽  
Atpase Subunits ◽  
Choroid Plexus Epithelial

(1) Background: The unusual accumulation of Na,K-ATPase complexes in the brush border membrane of choroid plexus epithelial cells have intrigued researchers for decades. However, the full range of the expressed Na,K-ATPase subunits and their relation to the microvillus cytoskeleton remains unknown. (2) Methods: RT-PCR analysis, co-immunoprecipitation, native PAGE, mass spectrometry, and differential centrifugation were combined with high-resolution immunofluorescence histochemistry, proximity ligase assays, and stimulated emission depletion (STED) microscopy on mouse choroid plexus cells or tissues in order to resolve these issues. (3) Results: The choroid plexus epithelium expresses Na,K-ATPase subunits α1, α2, β1, β2, β3, and phospholemman. The α1, α2, β1, and β2, subunits are all localized to the brush border membrane, where they appear to form a complex. The ATPase complexes may stabilize in the brush border membrane via anchoring to microvillar actin indirectly through ankyrin-3 or directly via other co-precipitated proteins. Aquaporin 1 (AQP1) may form part of the proposed multi-protein complexes in contrast to another membrane protein, the Na-K-2Cl cotransporter 1 (NKCC1). NKCC1 expression seems necessary for full brush border membrane accumulation of the Na,K-ATPase in the choroid plexus. (4) Conclusion: A multitude of Na,K-ATPase subunits form molecular complexes in the choroid plexus brush border, which may bind to the cytoskeleton by various alternative actin binding proteins.

scholarly journals Porcine Choroid Plexus Epithelial Cells Induce Streptococcus suis Bacteriostasis In Vitro

2004 ◽  
Vol 72 (5) ◽  
pp. 3084-3087 ◽  
Author(s):  
Rüdiger A. Adam ◽  
Tobias Tenenbaum ◽  
Peter Valentin-Weigand ◽  
Maurice Laryea ◽  
Bernd Schwahn ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Bacterial Meningitis ◽  
Choroid Plexus ◽  
Host Defense ◽  
Streptococcus Suis ◽  
Active Role ◽  
Necrosis Factor Alpha ◽  
Ifn Γ ◽  
Choroid Plexus Epithelial

ABSTRACT The involvement of the choroid plexus in host defense during bacterial meningitis is unclear. Aiming to elucidate possible antibacterial mechanisms, we stimulated primary porcine choroid plexus epithelial cells (pCPEC) with proinflammatory cytokines and challenged them with various Streptococcus suis strains. In the supernatant of gamma interferon (IFN-γ)-stimulated pCPEC, streptococcal growth was markedly suppressed. Costimulation with tumor necrosis factor alpha enhanced this bacteriostatic effect, while supplementation of l-tryptophan completely eliminated it. We also demonstrate that an activation of indoleamine 2,3-dioxygenase in the pCPEC seems to be responsible for the IFN-γ-induced bacteriostasis. This supports the hypothesis of an active role of the choroid plexus in host defense against bacterial meningitis.

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