Heterogeneous nuclear ribonucleoprotein K modulates angiotensinogen gene expression in kidney cells.
The present studies aimed to identify the 70-kDa nuclear protein that binds to an insulin-responsive element in the rat angiotensinogen gene promoter and to define its action on angiotensinogen gene expression. Nuclear proteins were isolated from rat kidney proximal tubular cells and subjected to two-dimensional electrophoresis. The 70-kDa nuclear protein was detected by Southwestern blotting and subsequently identified by mass spectrometry, which revealed that it was identical to 65-kDa heterogeneous nuclear ribonucleoprotein K (hnRNP K). hnRNP K bound to the insulin-responsive element of the rat angiotensinogen gene was revealed by a gel mobility shift assay and chromatin immunoprecipitation assay. hnRNP K inhibited angiotensinogen mRNA expression and promoter activity. In contrast, hnRNP K down-expression by small interference RNA enhanced angiotensinogen mRNA expression. Moreover, hnRNP K interacted with hnRNP F in pulldown and co-immunoprecipitation assays. Co-transfection of hnRNP K and hnRNP F further suppressed angiotensinogen mRNA expression. Finally, in vitro and in vivo studies demonstrated that high glucose increases and insulin inhibits hnRNP K expression in rat kidney proximal tubular cells. In conclusion, our experiments revealed that hnRNP K is a nuclear protein that binds to the insulin-responsive element of the rat angiotensinogen gene promoter and modulates angiotensinogen gene transcription in the kidney.
Wei
Chih-Chang
CC
Centre de Recherche, Centre Hospitalier de l'Université de Montréal-Hôtel-Dieu, Montreal, Quebec H2W 1T8, Canada.
Zhang
Shao-Ling
SL
Chen
Yun-Wen
YW
Guo
Deng-Fu
DF
Ingelfinger
Julie R
JR
Bomsztyk
Karol
K
Chan
John S D
JS
D000595:Amino Acid Sequence; D000808:Angiotensinogen / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D005947:Glucose / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D034641:Heterogeneous-Nuclear Ribonucleoprotein K / Q000378:metabolism / Q000502:physiology*; D007328:Insulin / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D051381:Rats
D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D007328:Insulin; D000808:Angiotensinogen; D005982:Glutathione Transferase; D005947:Glucose