Human fibroblast growth factor-23 mutants suppress Na+-dependent phosphate co-transport activity and 1alpha,25-dihydroxyvitamin D3 production.
The human fibroblast growth factor 23 (hFGF23) and its autosomal dominant hypophosphatemic rickets (ADHR) mutant genes were incorporated into animals by naked DNA injection to investigate the action on phosphate homeostasis in vivo. The hFGF23 mutants (R176Q, R179Q, and R179W) markedly reduced serum phosphorus (6.2-6.9 mg/dl) compared with the plasmid MOCK (8.5 mg/dl). However, native hFGF23 did not affect serum phosphorus (8.6 mg/dl). Both hFGF23 and hFGF23R179Q mRNAs were expressed more than 100-fold in the liver 4 days after injection, however, the C-terminal portion of hFGF23 was detected only in the serum from hFGF23R179Q-injected animals (1109 pg/ml). hFGF23R179Q mutant was secreted as a 32-kDa protein, whereas, native hFGF23 was detected as a 20-kDa protein in the cell-conditioned media. These results suggest the hFGF23R179Q protein is resistant to intracellular proteolytic processing. The hFGF23R179Q suppressed Na/P(i) co-transport activities both in kidney and in small intestine by 45 and 30%, respectively, as well as serum 1alpha,25-dihydroxyvitamin D(3) to less than 15 pg/ml. However, it had little effect on serum parathyroid hormone (PTH). Infusion of hFGF23R179Q protein normalized serum phosphorus in thyroparathyroidectomized rats without affecting serum calcium. Taken together, the FGF23 mutants reduce both phosphate uptake in intestine and phosphate reabsorption in kidney, independent of PTH action.
Saito
Hitoshi
H
Pharmaceutical Laboratory II, Chugai Pharmaceutical Co., Ltd., Shizuoka 412-8513, Japan. saitohts@chugai-pharm.co.jp
Kusano
Kenichiro
K
Kinosaki
Masahiko
M
Ito
Hirotaka
H
Hirata
Michinori
M
Segawa
Hiroko
H
Miyamoto
Ken-Ichi
K
Fukushima
Naoshi
N
D000225:Adenine / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D019556:COS Cells; D002762:Cholecalciferol / Q000378:metabolism*; D003001:Cloning, Molecular; D003404:Creatinine / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000235:genetics*; D018014:Gene Transfer Techniques; D006801:Humans; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice; D009154:Mutation; D009393:Nephritis / Q000097:blood; D010710:Phosphates / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors
D018076:DNA, Complementary; C000717427:FGF23 protein, human; C000717428:Fgf23 protein, mouse; D010710:Phosphates; D012333:RNA, Messenger; D002762:Cholecalciferol; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D012964:Sodium; D003404:Creatinine; D000225:Adenine