Expression and sub cellular localization of the sodium hydrogen exchanger isoform-1 in rat tissues: a possible functional relevance.
In an attempt to understand the mechanism underlying the tissue-dependent function, the expression of NHE-1 protein and its sub cellular localization was examined in the rat GI-tract and other tissues. Rat NHE-1 polyclonal antibodies were raised in rabbits using a NHE-1 fusion protein antigen. The antibodies recognized a 110 kD protein in rats and mice, but not in human or rabbit RBCs. Colon, stomach, brain, spleen and kidney expressed NHE-1 protein abundantly, whereas the skeletal muscle the least abundant. Ouabain-sensitive-K+-stimulated p-nitrophenylphosphatase (PNPPase), the partial activity of the sodium pump and alkaline phosphatase (Apase) were used as the markers of the basolateral and apical membranes. NHE-1 was detected predominantly in the PNPPase enriched membrane fractions, but was also detected in the apical membrane enriched fractions in the kidney cortex, jejunum and colon at a lower level. NHE-1 was detected in the plasma membrane enriched fractions from the skeletal muscle and ventricle. Immunofluorescence data showed a similar localization pattern of NHE-1 in the colon and kidney sections. These findings suggest that NHE-1 is localized both on the apical and basolateral membrane. In view of its similar sub cellular localization in the GI-tract and kidney, but a different level of expression, might suggest that the level of protein, but not the sub cellular distribution is important to regulate its tissue-dependent function.
Khan
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I
Department of Biochemistry, Faculty of Medicine, Kuwait University.
Thomas
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N
Haridas
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S
D009597:4-Nitrophenylphosphatase / Q000032:analysis; D000469:Alkaline Phosphatase / Q000032:analysis; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity; D003106:Colon / Q000378:metabolism; D003429:Cross Reactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007668:Kidney / Q000378:metabolism; D008861:Microsomes / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D010042:Ouabain / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012680:Sensitivity and Specificity; D017386:Sequence Homology, Amino Acid; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis; D014018:Tissue Distribution
D000906:Antibodies; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D011993:Recombinant Fusion Proteins; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D010042:Ouabain; D000469:Alkaline Phosphatase; D009597:4-Nitrophenylphosphatase; D000254:Sodium-Potassium-Exchanging ATPase