Pi transport, phosphorylation, and dephosphorylation in renal membranes from HYP/Y mice.
To ascertain whether cAMP-dependent phosphorylation could be demonstrated in brush border membrane vesicles (BBMV) isolated from kidneys of mice with X-linked hypophosphatemic rickets (HYP/Y) and normal littermates (+/Y) and, if so, to determine whether the absence of dephosphorylation might underlie differences in Na+-dependent 32Pi transport in BBMV, we measured 1) 32Pi transport, 2) cAMP-dependent phosphorylation, and 3) dephosphorylation in BBMV from +/Y and HYP/Y mice. Na+ gradient-dependent 32Pi transport was decreased in BBMV from HYP/Y mice as reflected in a decreased apparent Vmax. cAMP-dependent phosphorylation of a 62,000 Mr protein was demonstrated in sodium dodecyl sulfate polyacrylamide gels of BBMV from +/Y and HYP/Y mice and was associated with decreased Na+-dependent 32Pi transport. Dephosphorylation of the 62,000 Mr band was demonstrable in both types of membranes. Thus, both cAMP-dependent protein kinase and phosphoprotein phosphatase activities were demonstrable in BBMV isolated from +/Y and HYP/Y mice. These results are consistent with the renal tubular defect in the HYP/Y mouse reflecting an intrinsic abnormality of Pi transport in the brush border membrane independent from mediation of the phosphaturic effect of parathyroid hormone.
D000818:Animals; D001692:Biological Transport; D003433:Crosses, Genetic; D005260:Female; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D008871:Microvilli / Q000378:metabolism*; D008970:Molecular Weight; D010710:Phosphates / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D012964:Sodium / Q000494:pharmacology
D008565:Membrane Proteins; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D012964:Sodium