Cyclic AMP-dependent protein phosphorylation in canine renal brush-border membrane vesicles is associated with decreased phosphate transport.
It is known that the administration of parathyroid hormone to dogs results in phosphaturia and decreased phosphate transport in brush-border vesicles isolated from the kidneys of those dogs. Parathyroid hormone has been shown to activate adenylate cyclase at the basal-lateral membrane of the renal proximal tubular cell. It has been postulated that parathyroid hormone-induced phosphaturia is effected through phosphorylation of brush-border protein by membrane-bound cAMP-dependent protein kinase. An experimental system was designed such that phosphorylation of brush-border vesicles and Na+-stimulated solute transport could be studied in the same preparations. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of membrane vesicles revealed cAMP-dependent phosphorylation of 2 protein bands (Mr = 96,000 and 62,000), which was enhanced by exposure of the inside of the membrane vesicles to ATP and cAMP. Cyclic AMP-dependent phosphorylation of brush-border vesicles was accompanied by inhibition of Na+-stimulated Pi but not D-glucose transport or 22Na+ uptake. When renal brush-border vesicles from parathyroidectomized and normal dogs were phosphorylated in vitro in the presence and absence of cAMP, both the cAMP-dependent phosphorylation and inhibition of Na+-stimulated Pi transport were greater in vesicles isolated from kidneys of parathyroidectomized dogs relative to control animals. We conclude that the cAMP-dependent phosphorylation of brush-border membrane-vesicle proteins is associated with specific inhibition of Na+-stimulated Pi transport. The phosphaturic action of parathyroid hormone (PTH) could be mediated through the cAMP-dependent phosphorylation of specific brush-border membrane proteins.
D000818:Animals; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D004285:Dogs; D007672:Kidney Cortex / Q000378:metabolism*; D007700:Kinetics; D008563:Membrane Lipids / Q000378:metabolism*; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism*; D008970:Molecular Weight; D010710:Phosphates / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*
D008563:Membrane Lipids; D008565:Membrane Proteins; D010710:Phosphates; D000242:Cyclic AMP; D011494:Protein Kinases