Parathyroid hormone regulation of type II sodium-phosphate cotransporters is dependent on an A kinase anchoring protein.
Parathyroid hormone inhibits sodium-phosphate cotransport in proximal renal tubule cells through activation of several kinases. We tested the hypothesis that the activity of these kinases was coordinated by an A kinase anchoring protein (AKAP) by demonstrating that the type II sodium-phosphate cotransporter (NaPi-4) physically associated with an AKAP and that this association was necessary for regulation of phosphate transport by parathyroid hormone. Immunoprecipitation with anti-NaPi-4 antiserum and glutathione S-transferase pull-down with GST-NaPi-4 showed that NaPi-4 associated with AKAP79, protein kinase A catalytic and regulatory subunits, and the parathyroid hormone receptor in opossum kidney cells. When the regulatory subunit of protein kinase A was uncoupled from the AKAP by a competing peptide, parathyroid hormone lost the ability to inhibit phosphate transport. This result was confirmed by co-transfecting HEK293 cells with the sodium-phosphate cotransporter and wild type AKAP, a mutant AKAP79, or the empty vector. 8-Bromo-cAMP was able to inhibit phosphate transport in cells expressing the wild type AKAP79 but not empty vector or mutant AKAP79. We conclude that parathyroid hormone inhibits proximal renal tubule sodium-phosphate cotransport through a signaling complex dependent upon an AKAP.
Khundmiri
Syed Jalal
SJ
Kidney Disease Program, Department of Medicine, University of Louisville, Kentucky 40202, USA.
Rane
Madhavi J
MJ
Lederer
Eleanor D
ED
D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000502:physiology*; D002478:Cells, Cultured; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008969:Molecular Sequence Data; D009893:Opossums; D010281:Parathyroid Hormone / Q000502:physiology*; D011493:Protein Kinase C / Q000502:physiology; D018016:Receptors, Parathyroid Hormone / Q000502:physiology; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters / Q000737:chemistry / Q000502:physiology*
D054758:A Kinase Anchor Proteins; C487775:AKAP5 protein, human; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D010281:Parathyroid Hormone; D018016:Receptors, Parathyroid Hormone; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D027981:Symporters; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C