Effect of parathyroid hormone, cyclic AMP and Ca2+ on the phosphorylation of brush border membranes in rabbit kidney

• Published in: Mineral and electrolyte metabolism Vol. 10; no. 2; p. 103
• Main Authors: Takenawa, T, Wada, E, Tsumita, T, Masaki, T, Filburn, C R, Sacktor, B
• Format: Journal Article
• Language: English
• Published: Switzerland 1984
• Subjects: Animals; Bucladesine - pharmacology; Calcium - pharmacology; Cyclic AMP - pharmacology; Kidney Cortex - drug effects; Kidney Cortex - metabolism; Membrane Proteins - metabolism; Microvilli - metabolism; Octoxynol; Parathyroid Hormone - pharmacology; Phosphates - metabolism; Phosphorylation; Polyethylene Glycols - pharmacology; Rabbits
• ISSN: 0378-0392

Renal cortical slices were incubated with parathyroid hormone or dibutyryl cAMP and the effects on phosphate uptake and phosphorylation of proteins in brush border membranes isolated from the treated slices were determined. Na+ gradient-dependent phosphate uptake was inhibited. Phosphorylation of proteins of Mr=170 K, 135 K, 105 K, 88 K, and 68 K was increased after incubation with the hormone or the cyclic nucleotide. Phosphorylation of membrane proteins was also examined in isolated relatively intact brush border membrane vesicles and in membrane vesicles disrupted with Triton X-100. With intact membrane vesicles, total phosphorylation of the membrane was not significantly altered by cAMP. However, phosphorylation of proteins of Mr=85 K and 48 K increased whereas phosphorylation of proteins of Mr=170 K, 78 K, and 56 K decreased, relative to that found with slices. With detergent-treated membranes, which presumably were made permeable to [gamma-32P]-ATP, a cAMP-induced increase in total phosphorylation was demonstrated. Phosphorylation of proteins of Mr=135 K, 78 K, 65 K, and 56 K was markedly enhanced. These findings suggest that proteins of Mr=135 K, 78 K, 65 K, and 56 K are localized on the cytosolic side of the membrane whereas proteins of Mr=85 K and 48 K are present on the luminal surface of the membrane. Incubation of the isolated brush border membrane vesicles with Ca2+, or Ca2+ plus cAMP, also affected the phosphorylation of membrane proteins. The phosphorylation of proteins of Mr=105 K, 68 K, and 20 K was increased by Ca2+. The Mr=20 K protein may be myosin light chain.