De novo synthesis, uptake and proteolytic processing of lipocalin-type prostaglandin D synthase, beta-trace, in the kidneys.
Lipocalin-type prostaglandin D synthase (L-PGDS) is a multifunctional protein that produces prostaglandin D(2) and binds and transports various lipophilic substances after secretion into various body fluids as beta-trace. L-PGDS has been proposed to be a useful diagnostic marker for renal injury associated with diabetes or hypertension, because the urinary and plasma concentrations are increased in patients with these diseases. However, it remains unclear whether urinary L-PGDS is synthesized de novo in the kidney or taken up from the blood circulation. In crude extracts of monkey kidney and human urine, we found L-PGDS with its original N-terminal sequence starting from Ala23 after the signal sequence, and also its N-terminal-truncated products starting from Gln31 and Phe34. In situ hybridization and immunohistochemical staining with monoclonal antibody 5C11, which recognized the amino-terminal Ala23-Val28 loop of L-PGDS, revealed that both the mRNA and the intact form of L-PGDS were localized in the cells of Henle's loop and the glomeruli of the kidney, indicating that L-PGDS is synthesized de novo in these tissues. However, truncated forms of L-PGDS were found in the lysosomes of tubular cells, as visualized by immunostaining with 10A5, another monoclonal antibody, which recognized the three-turn alpha-helix between Arg156 and Thr173. These results suggest that L-PGDS is taken up by tubular cells and actively degraded within their lysosomes to produce the N-terminal-truncated form.
Nagata
Nanae
N
Department of Molecular Behavioral Biology, Osaka Bioscience Institute, Suita, Japan.
Fujimori
Ko
K
Okazaki
Issey
I
Oda
Hiroshi
H
Eguchi
Naomi
N
Uehara
Yoshio
Y
Urade
Yoshihiro
Y
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000882:Haplorhini; D006801:Humans; D017403:In Situ Hybridization; D019746:Intramolecular Oxidoreductases / Q000096:biosynthesis* / Q000235:genetics; D007668:Kidney / Q000201:enzymology* / Q000378:metabolism; D054834:Lipocalins / Q000096:biosynthesis* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D051381:Rats; D017207:Rats, Sprague-Dawley; D016415:Sequence Alignment
D000911:Antibodies, Monoclonal; D054834:Lipocalins; D019746:Intramolecular Oxidoreductases; C022466:prostaglandin R2 D-isomerase