Regulation of expression of type II sodium-phosphate cotransporters by protein kinases A and C.
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.
Lederer
E D
ED
Department of Internal Medicine, Veterans Affairs Medical Center, Louisville 40206; and Department of Internal Medicine, University of Louisville, Louisville, Kentucky 40202-1718, USA.
Sohi
S S
SS
Mathiesen
J M
JM
Klein
J B
JB
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D005786:Gene Expression Regulation / Q000187:drug effects; D015151:Immunoblotting; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D009893:Opossums; D010281:Parathyroid Hormone / Q000494:pharmacology / Q000502:physiology; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology; D011817:Rabbits; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000906:Antibodies; D002352:Carrier Proteins; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D010710:Phosphates; D011506:Proteins; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters; C067924:parathyroid hormone-related protein (3-34); D015124:8-Bromo Cyclic Adenosine Monophosphate; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate