Ochratoxin A impairs ?postproximal? nephron function in vivo and blocks plasma membrane anion conductance in Madin-Darby canine kidney cells in vitro

1993 ◽  
Vol 425 (5-6) ◽  
pp. 401-408 ◽  
Author(s):  
Michael Gekle ◽  
Hans Oberleithner ◽  
Stefan Silbernagl
2019 ◽  
Vol 317 (1) ◽  
pp. F30-F42
Author(s):  
Te-Jung Lu ◽  
Wei-Chih Kan ◽  
Sung-Sen Yang ◽  
Si-Tse Jiang ◽  
Sheng-Nan Wu ◽  
...  

Liddle syndrome is an inherited form of human hypertension caused by increasing epithelial Na+ channel (ENaC) expression. Increased Na+ retention through ENaC with subsequent volume expansion causes hypertension. In addition to ENaC, the Na+-K+-Cl− cotransporter (NKCC) and Na+-Cl− symporter (NCC) are responsible for Na+ reabsorption in the kidneys. Several Na+ transporters are evolutionarily regulated by the Ste20 kinase family. Ste20-related proline/alanine-rich kinase and oxidative stress-responsive kinase-1 phosphorylate downstream NKCC2 and NCC to maintain Na+ and blood pressure (BP) homeostasis. Mammalian Ste20 kinase 3 (MST3) is another member of the Ste20 family. We previously reported that reduced MST3 levels were found in the kidneys in spontaneously hypertensive rats and that MST3 was involved in Na+ regulation. To determine whether MST3 is involved in BP stability through Na+ regulation, we generated a MST3 hypomorphic mutation and designated MST3+/− and MST3−/− mice to examine BP and serum Na+ and K+ concentrations. MST3−/− mice exhibited hypernatremia, hypokalemia, and hypertension. The increased ENaC in the kidney played roles in hypernatremia. The reabsorption of more Na+ promoted more K+ secretion in the kidney and caused hypokalemia. The hypernatremia and hypokalemia in MST3−/− mice were significantly reversed by the ENaC inhibitor amiloride, indicating that MST3−/− mice reabsorbed more Na+ through ENaC. Furthermore, Madin-Darby canine kidney cells stably expressing kinase-dead MST3 displayed elevated ENaC currents. Both the in vivo and in vitro results indicated that MST3 maintained Na+ homeostasis through ENaC regulation. We are the first to report that MST3 maintains BP stability through ENaC regulation.


1983 ◽  
Vol 97 (5) ◽  
pp. 1365-1374 ◽  
Author(s):  
G van Meer ◽  
K Simons

An efficient method has been devised to introduce lipid molecules into the plasma membrane of mammalian cells. This method has been applied to fuse lipid vesicles with the apical plasma membrane of Madin-Darby canine kidney cells. The cells were infected with fowl plague or influenza N virus. 4 h after infection, the hemagglutinin (HA) spike glycoprotein of the virus was present in the apical plasma membrane of the cells. Lipid vesicles containing egg phosphatidylcholine, cholesterol, and an HA receptor (ganglioside) were then bound to the cells at 0 degrees C. More than 85% of the vesicles were released by external neuraminidase at 0 degrees C or by simply warming the cells to 37 degrees C for 10 s, probably because of the action of the viral neuraminidase at the cell surface. However, when the cells were warmed to 37 degrees C in a pH 5.3 medium for 30 s, 50% of the bound vesicles could no longer be released by external neuraminidase. This only occurred when the HA protein had been cleaved into its HA1 and HA2 subunits. When we used influenza N virus, whose HA is not cleaved in Madin-Darby canine kidney cells, cleavage with external trypsin was required. The fact that the HA protein has fusogenic properties at low pH only in its cleaved form suggests that fusion of the vesicles with the plasma membrane had taken place. Further confirmation for fusion was obtained using an assay based on the decrease of energy transfer between two fluorescent phospholipids in a vesicle upon fusion of the vesicle with the plasma membrane (Struck, D. K., D. Hoekstra, and R. E. Pagano. 1981. Biochemistry, 20:4093-4099).


1984 ◽  
Vol 99 (3) ◽  
pp. 796-782 ◽  
Author(s):  
M Pesonen ◽  
W Ansorge ◽  
K Simons

The G protein of vesicular stomatitis virus, implanted into the apical plasma membrane of Madin-Darby canine kidney cells, is rapidly transcytosed to the basolateral membrane. In this and the accompanying paper (Pesonen, M., R. Bravo, and K. Simons, 1984, J. Cell Biol. 99:803-809.) we have studied the intracellular route by which the G protein traverses during transcytosis. Using Percoll density gradient centrifugation and free flow electrophoresis we could demonstrate that the G protein is endocytosed into a nonlysosomal compartment with a density of approximately 1.05 g/cm3, which has many of the characteristics of endosomes. Transcytosis to the basolateral membrane appeared to occur from this compartment. No direct evidence for the involvement of lysosomes in the transcytotic route could be obtained. No G protein was detected in the lysosomes when transcytosis of G protein was occurring. Moreover, at 21 degrees C when passage of G protein to the lysosomes was shown to be arrested, transcytosis of G protein could still be demonstrated.


1983 ◽  
Vol 97 (3) ◽  
pp. 638-643 ◽  
Author(s):  
M Pesonen ◽  
K Simons

The envelope of vesicular stomatitis virus was fused with the apical plasma membrane of Madin-Darby canine kidney cells by low pH treatment. The fate of the implanted G protein was then followed using a protein A-binding assay, which was designed to quantitate the amount of G protein in the apical and the basolateral membranes. The implanted G protein was rapidly internalized at 31 degrees C, whereas at 10 degrees C no uptake was observed. Already after 15 min at 31 degrees C, a fraction of the G protein could be detected at the basolateral membrane. After 60 min 25-48% of the G protein was basolateral as measured by the protein A-binding assay. At the same time, 25-33% of the implanted G protein was detected at the apical membrane. Internalization of G protein was not affected by 20 mM ammonium chloride or by 10 microM monensin. However, the endocytosed G protein accumulated in intracellular vacuoles and redistribution back to the plasma membrane was inhibited. We conclude that the implanted G protein was rapidly internalized from the apical surface of Madin-Darby canine kidney cells and a major fraction was routed to the basolateral domain.


1990 ◽  
Vol 96 (1) ◽  
pp. 143-149
Author(s):  
J.M. Wilson ◽  
N. Fasel ◽  
J.P. Kraehenbuhl

Madin-Darby canine kidney cells (MDCK) were transfected with a cDNA encoding the glycosyl-phosphatidylinositol (GPI)-anchored protein mouse Thy-1 in order to study the steady-state surface distribution of exogenous and endogenous GPI-linked proteins. Immunofluorescence of transfected cells grown on collagen-coated coverslips showed that expression of Thy-1 was variable throughout the epithelium, with some cells expressing large amounts of Thy-1 adjacent to very faintly staining cells. Selective surface iodination of cells grown on collagen-coated or uncoated transwell filters followed by immunoprecipitation of Thy-1 demonstrated that all the Thy-1 was present exclusively in the apical plasma membrane. Although cells grown on uncoated filters had much smaller amounts of Thy-1, it was consistently localized on the apical surfaces. Immunofluorescent localization of Thy-1 on 1 micron frozen sections of filter-grown cells demonstrated that all the Thy-1 was on the apical surface and there was no detectable intracellular pool. Phosphatidylinositol-specific phospholipase C digestion of intact iodinated monolayers released Thy-1 only into the apical medium, indicating that Thy-1 was processed normally in transfected cells and was anchored by a GPI-tail. In agreement with previous findings, endogenous GPI-linked proteins were found only on the apical plasma membrane. These results suggest that there is a common mechanism for sorting and targeting of GPI-linked proteins in polarized epithelial cells.


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