期刊
AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY
卷 279, 期 4, 页码 C1135-C1143出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpcell.2000.279.4.C1135
关键词
Na-P-i-III; amphotropic murine retrovirus receptor; Ram-1; sodium-dependent phosphate cotransporter; sodium-phosphate transporter; Pit-2
资金
- NIDDK NIH HHS [2R01-R37DK33209] Funding Source: Medline
Intestinal and renal absorption of inorganic phosphate (P-i) is critical for phosphate homeostasis in mammals. We have isolated a cDNA that encodes a type III Na-dependent phosphate cotransporter from mouse small intestine (mPit-2). The nucleotide sequence of mPit-2 predicts a protein of 653 amino acids with at least 10 putative transmembrane domains. Kinetic studies, carried out in Xenopus oocytes, showed that mPit-2 cRNA induces significant Na-dependent P-i uptake with an apparent Michaelis constant (K-m) for phosphate of 38 mu M. The transport of phosphate by mPit-2 is inhibited at high pH. Northern blot analysis demonstrated the presence of mPit-2 mRNA in various tissues, including intestine, kidney, heart, liver, brain, testis, and skin. The highest expression of mPit-2 in the intestine was found in the jejunum. In situ hybridization revealed that mPit-2 mRNA is expressed throughout the vertical crypt-villus axis of the intestinal epithelium. The presence of mPit-2 in the mouse intestine and its unique transport characteristics suggest that multiple Na-dependent cotransporters may contribute to phosphate absorption in the mammalian small intestine.
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