Abstract
We reported previously an IRE in rat ANG gene promoter that binds to two nuclear proteins with apparent molecular weights of 48- and 70-kDa from rat immortalized renal proximal tubular cells (IRPTCs). We recently identified the 48-kDa nuclear protein as the 46 kDa heterogenous nuclear ribonucleoprotein F (hnRNP F) that binds to rANG-IRE and inhibits ANG gene expression in IRPTCs. The present studies aimed to clone the 70-kDa nuclear protein and to study its action on ANG gene expression. Nuclear proteins isolated from IRPTCs were subjected to 2-dimensional gel 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 hnRNP K. Transient transfection of hnRNP K cDNA inhibits ANG mRNA expression and ANG gene promoter activity in IRPTCs. Most interestingly, hnRNP K pulls down with hnRNP F. Co-transfection of hnRNP K with hnRNP F positively regulates ANG gene expression in IRPTCs. In conclusion, our studies demonstrate that 65-kDa hnRNP K is a novel nuclear protein that interacts with hnRNP F and binds to IRE of the rat ANG gene promoter and subsequently modulates ANG gene expression in IRPTCs. These data indicate that 65-kDa hnRNP K plays an important role in modulating intrarenal ANG gene expression and renin-angiotensin system activation and subsequently kidney injury. These observations open a novel research route to study renal ANG gene regulation.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have