title: Role of Rho small GTPases in meniscus cells.
abstract: We previously reported that mechanical stretch regulates Sry-type HMG box (SOX) 9-dependent α1(II) collagen (COL2A1) expression in inner meniscus cells. This study examined the role of the small Rho guanosine 5' triphosphatase Rac1 and Rho-associated kinase (ROCK) in the regulation of stretch-induced SOX9 gene expression in cultured human inner meniscus cells. COL2A1 and SOX9 gene expression was assessed by real-time PCR after application of uni-axial cyclic tensile strain (CTS) in the presence or absence of ROCK and Rac1 inhibitors. The subcellular localization of SOX9 and the Rac1 effector cyclic AMP response element-binding protein (CREB), the phosphorylation state of SOX9, Rac1 activation, and the binding of CREB to the SOX9 promoter were assessed. CTS increased the expression of COL2A1 and SOX9, which was suppressed by inhibition of Rac1. ROCK inhibition enhanced COL2A1 and SOX9 gene expression in the absence of CTS. CTS stimulated the nuclear translocation and phosphorylation of SOX9, and increased Rac1 activation. CTS also increased the binding of CREB to the SOX9 promoter. The results suggest that mechanical stretch-dependent upregulation of SOX9 by CREB in inner meniscus cells depends on the antagonistic activities of ROCK and Rac1.
authors.affiliation: Department of Orthopaedic Surgery, Science of Functional Recovery and Reconstruction, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikatacho, Kitaku, Okayama, 700-8558, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kanazawa
authors.forename: Takayuki
authors.initials: T
authors.lastname: Furumatsu
authors.forename: Emi
authors.initials: E
authors.lastname: Matsumoto-Ogawa
authors.forename: Ami
authors.initials: A
authors.lastname: Maehara
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Ozaki
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D002356:Cartilage / Q000201:enzymology*; D024043:Collagen Type II / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007717:Knee / Q000502:physiology*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D051381:Rats; D055758:SOX9 Transcription Factor / Q000378:metabolism; D013314:Stress, Mechanical; D013718:Tensile Strength; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: C499177:COL2A1 protein, human; C115163:CREB1 protein, human; D024043:Collagen Type II; D017362:Cyclic AMP Response Element-Binding Protein; C107953:RAC1 protein, human; D055758:SOX9 Transcription Factor; C527932:SOX9 protein, human; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins
keywords: CREB; Mechanical stretch; Meniscus; ROCK; Rac1; SOX9