Abstract
The purpose of the present study was to determine the effect of protein kinase A and protein kinase C activation on the membrane expression of NaPi-4, the type II sodium-phosphate cotransporter in OK cells. NaPi-4 expression was measured using polyclonal antisera produced in rabbits against a peptide identical to the carboxy-terminal 12-amino acid sequence of NaPi-4. The antisera identified an apically localized protein by confocal imaging of intact OK cells and a broad band of 110-140 kDa by immunoblot analysis of OK cell membranes. Treatment of OK cells with parathyroid hormone (PTH) decreased the intensity of the 110- to 140-kDa band, which was detectable by 2 h, maximal by 4 h at 62%, and sustained for 24 h. 8-Bromo-cAMP (8-BrcAMP) inhibited NaPi-4 expression for up to 24 h by over 90%. However, phorbol 12-myristate 13-acetate inhibited NaPi-4 expression by less than 10%. PTH-(3-34), a fragment which stimulates only protein kinase C, inhibited phosphate transport but also had no effect on NaPi-4 expression. We conclude that protein kinase A but not protein kinase C inhibits sodium-phosphate uptake in OK cells by downregulation of NaPi-4 expression.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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8-Bromo Cyclic Adenosine Monophosphate / pharmacology
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Amino Acid Sequence
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Animals
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Antibodies
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Carrier Proteins / biosynthesis
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Carrier Proteins / genetics*
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Cell Line
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Cell Membrane / physiology
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Cyclic AMP-Dependent Protein Kinase Type II
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Cyclic AMP-Dependent Protein Kinases / metabolism*
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Enzyme Activation
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Gene Expression Regulation* / drug effects
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Immunoblotting
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Kidney / metabolism*
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Kinetics
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Opossums
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Parathyroid Hormone / pharmacology
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Parathyroid Hormone / physiology
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Parathyroid Hormone-Related Protein*
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Peptide Fragments / chemistry
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Peptide Fragments / immunology
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Peptide Fragments / pharmacology
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Phosphates / metabolism
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Protein Kinase C / metabolism*
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Proteins / pharmacology
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Rabbits
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Sodium-Phosphate Cotransporter Proteins
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Sodium-Phosphate Cotransporter Proteins, Type II
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Symporters*
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Tetradecanoylphorbol Acetate / pharmacology
Substances
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Antibodies
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Carrier Proteins
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Parathyroid Hormone
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Parathyroid Hormone-Related Protein
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Peptide Fragments
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Phosphates
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Proteins
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Sodium-Phosphate Cotransporter Proteins
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Sodium-Phosphate Cotransporter Proteins, Type II
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Symporters
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parathyroid hormone-related protein (3-34)
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8-Bromo Cyclic Adenosine Monophosphate
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Cyclic AMP-Dependent Protein Kinase Type II
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Cyclic AMP-Dependent Protein Kinases
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Protein Kinase C
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Tetradecanoylphorbol Acetate