title: KPNA2 interacts with P65 to modulate catabolic events in osteoarthritis.
abstract: OBJECTIVE
  Karyopherin alpha 2 (KPNA2) is a member of the importin α family, which acts as an adaptor to deliver P65 to the nucleus by recognizing the classic nuclear localization signal (NLS) of the cargo protein, and which has been reported as being involved in the pathogenesis of many diseases. This study was undertaken to determine the expression and possible functions of KPNA2 in osteoarthritis (OA).
  
  
  METHODS
  KPNA2 expression in cartilage tissues of OA patients and normal controls was detected by RT-PCR and immunohistochemistry. SW1353 cells were stimulated with IL-1β to establish the chondrocyte injury model in vitro. The expression of KPNA2 and catabolic genes in IL-1β-treated SW1353 cells were determined by Western blot. The interaction between KPNA2 and P65 was analyzed by co-immunoprecipitation, the subcellular distribution and transportation of P65 were detected by the subcellular fractionation followed by immunoblot analysis and immunofluorescence. Furthermore, we used RNA interference to analyze the role of KPNA2 in IL-1β-induced P65 nuclear importation and MMP13, ADAMTS-5 expression in SW1353 cells.
  
  
  RESULTS
  Cartilage expression of KPNA2 was higher in patients with OA compared with normal controls and mainly locating in chondrocytes. In IL-1β-treated SW1353 cells, up-regulation of KPNA2 was accompanied by the elevated expression of the catabolic marker protein levels, including MMP13 and ADAMTS-5, and increased NF-κB P65 nuclear importation. Knock-down of KPNA2 resulted in decreased catabolic marker protein levels in IL-1β-treated SW1353 cells. KPNA2 interacted with p65, and loss of KPNA2 caused decreased nuclear translocation of the active p50/p65 NF-κB complex.
  
  
  CONCLUSIONS
  These findings suggested that KPNA2 may promote NF-κB activation via facilitating P65 nuclear transportation, and thus subsequently accelerate the catabolic events of osteoarthritis.
authors.affiliation: Department of Orthopaedics, Affiliated Hospital of Nantong University and Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Nantong University, Nantong 226001, China.
authors.forename: Ran
authors.initials: R
authors.lastname: Tao
authors.affiliation: Department of Orthopaedics, Affiliated Hospital of Nantong University and Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Nantong University, Nantong 226001, China.
authors.forename: Xinbao
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Orthopaedics, Affiliated Hospital of Nantong University and Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Nantong University, Nantong 226001, China.
authors.forename: Chi
authors.initials: C
authors.lastname: Sun
authors.affiliation: Department of Orthopaedics, Affiliated Hospital of Nantong University and Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Nantong University, Nantong 226001, China.
authors.forename: Youhua
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Orthopaedics, Affiliated Hospital of Nantong University and Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Nantong University, Nantong 226001, China.
authors.forename: Shitao
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Orthopaedics, Affiliated Hospital of Nantong University and Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Nantong University, Nantong 226001, China.
authors.forename: Zhongbing
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Orthopaedics, Affiliated Hospital of Nantong University and Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Nantong University, Nantong 226001, China.
authors.forename: Leilei
authors.initials: L
authors.lastname: Zhai
authors.affiliation: Department of Orthopaedics, Traditional Chinese Medical Hospital of Nantong City, Nantong 226001, China.
authors.forename: Hongbing
authors.initials: H
authors.lastname: Cheng
authors.affiliation: National Glycoengineering Research Center and State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China.
authors.forename: Min
authors.initials: M
authors.lastname: Xiao
authors.affiliation: Department of Orthopaedics, Affiliated Hospital of Nantong University and Jiangsu Province Key Laboratory for Inflammation and Molecular Drug Target, Nantong University, Nantong 226001, China; Department of Pathogen Biology, Medical College, Nantong University, Nantong 226001, China. Electronic address: zdm@ntu.edu.cn.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Zhang
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D000071116:ADAMTS5 Protein; D015415:Biomarkers / Q000378:metabolism*; D015153:Blotting, Western; D016022:Case-Control Studies; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D053583:Interleukin-1beta / Q000494:pharmacology; D008297:Male; D053509:Matrix Metalloproteinase 13 / Q000235:genetics / Q000378:metabolism; D008875:Middle Aged; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D010003:Osteoarthritis / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism*; D028901:alpha Karyopherins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D053583:Interleukin-1beta; C490630:KPNA2 protein, human; D016328:NF-kappa B; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051996:Transcription Factor RelA; D028901:alpha Karyopherins; D051722:ADAM Proteins; D000071116:ADAMTS5 Protein; C121532:ADAMTS5 protein, human; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13
keywords: ADAMTS-5; KPNA2; MMP13; Osteoarthritis; P65; SW1353 cells