Citrullination preferentially proceeds in glomerular Bowman's capsule and increases in obstructive nephropathy.
BACKGROUND
Peptidylarginine deiminases (PADs) are a group of posttranslational modification enzymes that citrullinate (deiminate) protein arginine residues, yielding citrulline residues. Citrullination of arginine residues abolishes their positive charge, markedly altering their structure. We undertook this study to investigate the actions of PADs in the kidney.


METHODS
In male rats, we ligated the unilateral ureter, then analyzed the obstructed and contralateral kidneys 1 week later. Controls were rats simultaneously given sham operations. In another experiment, we ligated unilateral ureters of eight rats, four of which received a ureter-bladder anastomosis 1 week later. These rats were subjected to histologic examinations 5 weeks after unilateral ureteral obstruction (UUO).


RESULTS
Reverse transcription-polymerase chain reaction (RT-PCR) revealed that, of PADs (type I, II, III, and IV), only PAD type II was expressed in kidneys. Western blot study showed that PAD type II expression and citrullinated protein content increased greatly in kidneys that underwent unilateral ureteral ligation compared to that in contralateral or sham-operated kidneys. Immunohistochemical analyses revealed that PAD type II was preferentially expressed by parietal epithelial cells and that only in Bowman's capsule were proteins citrullinated. Additionally, these PAD type II and citrullinated proteins in obstructed nephropathy were significantly attenuated by the release of the obstruction. Proteome analysis revealed that one of citrullinated proteins in the kidney should be actin.


CONCLUSIONS
This result indicates that PAD type II and citrullinated proteins are suitable markers of Bowman's capsule. Not only are these markers preferentially expressed in Bowman's capsules but their expression is also increased in damaged kidneys by UUO, features that promise the further clarification of kidney diseases.
Feng
Dongyun
D
Department of Molecular Pathology, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.
Imasawa
Toshiyuki
T
Nagano
Tadasuke
T
Kikkawa
Masaru
M
Takayanagi
Kaori
K
Ohsawa
Takako
T
Akiyama
Kyoichi
K
Ishigami
Akihito
A
Toda
Tosifusa
T
Mitarai
Tetsuya
T
Machida
Takeo
T
Maruyama
Naoki
N
D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D015415:Biomarkers; D001806:Blood Urea Nitrogen; D002956:Citrulline / Q000378:metabolism*; D003404:Creatinine / Q000097:blood; D004847:Epithelial Cells / Q000201:enzymology; D006867:Hydrolases / Q000235:genetics; D007678:Kidney Glomerulus / Q000378:metabolism* / Q000503:physiopathology*; D008297:Male; D010449:Peptide Mapping; D000080064:Protein-Arginine Deiminase Type 2; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D014517:Ureteral Obstruction / Q000378:metabolism* / Q000503:physiopathology*
D015415:Biomarkers; D012333:RNA, Messenger; D002956:Citrulline; D003404:Creatinine; D006867:Hydrolases; C461539:Padi2 protein, rat; D000080064:Protein-Arginine Deiminase Type 2