title: AKT regulation of mesothelial-to-mesenchymal transition in peritoneal dialysis is modulated by Smurf2 and deubiquitinating enzyme USP4.
abstract: BACKGROUND
  Transforming growth factor-β1 (TGF-β1) plays a key role in mesothelial-to-mesenchymal transition (MMT) during peritoneal dialysis (PD). However, the role of Akt in MMT transformation in PD is not clear.
  
  
  RESULTS
  In this study, we observed that the phosphorylated form of protein kinase B (Akt), termed as pAkt, was up-regulated in the peritoneum of mice undergoing PD. It was associated with thickening of the peritoneum and up-regulation of TGF-β1. Upregulation of pAkt paralleled with the increased expression of Smad ubiquitination regulatory factor 2 (Smurf2), Vimentin and fibronectin (FN), and decreased expression of mothers against decapentaplegic homolog 7 (Smad7) and Zonula Occludens protein 1(ZO-1) in mice undergoing PD treatment and in TGF-β1 induced human peritoneal mesothelial cells (HPMCs). These changes were reversed with the treatment of a PI3K/Akt inhibitor LY294002 in vivo or in cells transfected with Akt dominant-negative (Akt-DN) plasmids in vitro. Increased Smurf2 expression in HPMCs, induced by TGF-β1 was accompanied with altered expression of Transforming growth factor receptor I (TβR-I), Smad7, ZO-1, Vimentin and FN via Akt modulation. In addition, inhibition of Ubiquitin carboxyl-terminal hydrolase 4 (USP4) decreased TGF- β1-induced expression of TβR-I and reversed the altered expression of Smad7, Smurf2, ZO-1 and Vimentin. Moreover, TGF-β1 accentuated the interactions between Smurf2 and Smad7, while reduced the association between TβR-I and Smurf2. These interactions were reversed by the treatment of Akt-DN and USP4 siRNA, respectively.
  
  
  CONCLUSIONS
  These data implied that Akt mediated MMT in PD via Smurf2 modulation/and or Smad7 degradation while conceivably maintaining the TβRI stability, most likely by the USP4.
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. xiaolidoc@aliyun.com.
authors.forename: Li
authors.initials: L
authors.lastname: Xiao
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. pengxiangxy@163.com.
authors.forename: Xiang
authors.initials: X
authors.lastname: Peng
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. liufuyoukidney@163.com.
authors.forename: Fuyou
authors.initials: F
authors.lastname: Liu
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. Tangcy12@163.com.
authors.forename: Chengyuan
authors.initials: C
authors.lastname: Tang
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. huchunly@126.com.
authors.forename: Chun
authors.initials: C
authors.lastname: Hu
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. xu129214@163.com.
authors.forename: Xiaoxuan
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. wangminggoodlk@163.com.
authors.forename: Ming
authors.initials: M
authors.lastname: Wang
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. luoying2420@163.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. ysk_1234@163.com.
authors.forename: Shikun
authors.initials: S
authors.lastname: Yang
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. spa863@163.com.
authors.forename: Panai
authors.initials: P
authors.lastname: Song
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. xiaopingxy3366@163.com.
authors.forename: Ping
authors.initials: P
authors.lastname: Xiao
authors.affiliation: Departments of Pathology & Medicine, Northwestern University, Chicago, USA. y-kanwar@northwestern.edu.
authors.forename: Yashpal S
authors.initials: YS
authors.lastname: Kanwar
authors.affiliation: Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China. sunlinnwu11@163.com.
authors.forename: Lin
authors.initials: L
authors.lastname: Sun
mesh_terms: D000818:Animals; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects; D005260:Female; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D010530:Peritoneal Dialysis; D010537:Peritoneum / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051906:Smad7 Protein / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism / Q000494:pharmacology; D043222:Ubiquitin Thiolesterase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D064570:Ubiquitin-Specific Proteases; D015854:Up-Regulation / Q000187:drug effects; D014746:Vimentin / Q000235:genetics / Q000378:metabolism; D062826:Zonula Occludens-1 Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D002867:Chromones; D005353:Fibronectins; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D051906:Smad7 Protein; D053773:Transforming Growth Factor beta1; D043222:Ubiquitin Thiolesterase; D044767:Ubiquitin-Protein Ligases; D064570:Ubiquitin-Specific Proteases; D014746:Vimentin; D062826:Zonula Occludens-1 Protein; C569043:Tjp1 protein, mouse; C082325:Usp4 protein, mouse; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C533325:Smurf2 protein, mouse