Renal Na(+)-phosphate cotransport in murine X-linked hypophosphatemic rickets. Molecular characterization.
The X-linked Hyp mouse is characterized by a specific defect in proximal tubular phosphate (Pi) reabsorption that is associated with a decrease in Vmax of the high affinity Na(+)-Pi cotransport system in the renal brush border membrane. To understand the mechanism for Vmax reduction, we examined the effect of the Hyp mutation on renal expression of Na(+)-Pi cotransporter mRNA and protein. Northern hybridization of renal RNA with a rat, renal-specific Na(+)-Pi cotransporter cDNA probe (NaPi-2) (Magagnin et al. 1993. Proc. Natl. Acad. Sci. USA. 90:5979-5983.) demonstrated a reduction in a 2.6-kb transcript in kidneys of Hyp mice relative to normal littermates (NaPi-2/beta-actin mRNA = 57 +/- 6% of normal in Hyp mice, n = 6, P < 0.01). Na(+)-Pi cotransport, but not Na(+)-sulfate cotransport, was approximately 50% lower in Xenopus oocytes injected with renal mRNA extracted from Hyp mice when compared with that from normal mice. Hybrid depletion experiments documented that the mRNA-dependent expression of Na(+)-Pi cotransport in oocytes was related to NaPi-2. Western analysis demonstrated that NaPi-2 protein is also significantly reduced in brush border membranes of Hyp mice when compared to normals. The present data demonstrate that the specific reduction in renal Na(+)-Pi cotransport in brush border membranes of Hyp mice can be ascribed to a proportionate decrease in the abundance of Na(+)-Pi cotransporter mRNA and protein.
Tenenhouse
H S
HS
McGill University-Montreal Children's Hospital Research Institute, Department of Pediatrics, Quebec, Canada.
Werner
A
A
Biber
J
J
Ma
S
S
Martel
J
J
Roy
S
S
Murer
H
H
D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D003433:Crosses, Genetic; D005260:Female; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism; D007015:Hypophosphatemia, Familial / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008871:Microvilli / Q000378:metabolism; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010710:Phosphates / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D050608:Sodium-Phosphate Cotransporter Proteins; D013431:Sulfates / Q000378:metabolism; D027981:Symporters; D014960:X Chromosome
D002352:Carrier Proteins; D009838:Oligodeoxyribonucleotides; D010710:Phosphates; D012333:RNA, Messenger; D050608:Sodium-Phosphate Cotransporter Proteins; D013431:Sulfates; D027981:Symporters; D012964:Sodium; D005947:Glucose