title: S100A4 regulates the Src-tyrosine kinase dependent differentiation of Th17 cells in rheumatoid arthritis.
abstract: OBJECTIVE
  To evaluate the role of S100A4, a calcium-binding regulator of nonmuscle myosin assembly, for T-cell responses in rheumatoid arthritis.
  
  
  METHODS
  Arthritis was induced in the methylated bovine serum albumin (mBSA)-immunized mice lacking the entire S100A4 protein (S100A4KO) and in wild-type counterparts treated with short hairpin ribonucleic acid (shRNA)-lentiviral constructs targeting S100A4 (S100A4-shRNA). The severity of arthritis was evaluated morphologically. T-cell subsets were characterized by the expression of master transcription factors, and functionally by proliferation activity and cytokine production. The activity of the Scr-kinases Fyn and Lck was assessed by the autophosphorylation of C-terminal thyrosine and by the phosphorylation of the CD5 cytodomain. The interaction between S100A4 and the CD5 cytodomain was analysed by nuclear magnetic resonance spectrophotometry.
  
  
  RESULTS
  S100A4-deficient mice (S100A4KO and S100A4-shRNA) had significantly alleviated morphological signs of arthritis and joint damage. Leukocyte infiltrates in the arthritic joints of S100A4-deficient mice accumulated Foxp3(+) Treg cells, while the number of RORγt(+) and (pTyr705)STAT3(+) cells was reduced. S100A4-deficient mice had a limited formation of Th17-cells with low retinoic acid orphan receptor gamma t (RORγt) mRNA and IL17 production in T-cell cultures. S100A4-deficient mice had a low expression and activity of T-cell receptor (TCR) inhibitor CD5 and low (pTyr705)STAT3 (signal transducer and activator of transcription 3), which led to increased (pTyr352)ZAP-70 (theta-chain associated protein kinase of 70kDa), lymphocyte proliferation and production of IL2. In vitro experiments showed that S100A4 directly binds Lck and Fyn and reciprocally regulates their kinase activity towards the CD5 cytodomain. Spectrometry demonstrates an interaction between the CD5 cytodomain and EF2-binding sites of S100A4.
  
  
  CONCLUSIONS
  The present study demonstrates that S100A4 plays an important part in the pathogenesis of arthritis. It controls CD5-dependent differentiation of Th17 cells by regulating the activity of the Src-family kinases Lck and Fyn.
authors.affiliation: Department of Rheumatology and Inflammation Research, The Sahlgren's Academy at University of Gothenburg, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Brisslert
authors.affiliation: Department of Rheumatology and Inflammation Research, The Sahlgren's Academy at University of Gothenburg, Sweden.
authors.forename: Li
authors.initials: L
authors.lastname: Bian
authors.affiliation: Department of Rheumatology and Inflammation Research, The Sahlgren's Academy at University of Gothenburg, Sweden.
authors.forename: Mattias N D
authors.initials: MN
authors.lastname: Svensson
authors.affiliation: IBMC - Instituto de Biologia Molecular e Celular, University of Porto, Portugal.
authors.forename: Rita F
authors.initials: RF
authors.lastname: Santos
authors.affiliation: Department of Rheumatology and Inflammation Research, The Sahlgren's Academy at University of Gothenburg, Sweden.
authors.forename: Ing-Marie
authors.initials: IM
authors.lastname: Jonsson
authors.affiliation: Department of Structural and Chemical Biology, Institute of Integrative Biology, University of Liverpool, United Kingdom.
authors.forename: Igor
authors.initials: I
authors.lastname: Barsukov
authors.affiliation: Department of Rheumatology and Inflammation Research, The Sahlgren's Academy at University of Gothenburg, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Erlandsson
authors.affiliation: Department of Rheumatology and Inflammation Research, The Sahlgren's Academy at University of Gothenburg, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Andersson
authors.affiliation: IBMC - Instituto de Biologia Molecular e Celular, University of Porto, Portugal; ICBAS - Instituto de Ciencias Biomedicas Abel Salazar, University of Porto, Portugal.
authors.forename: Alexandre M
authors.initials: AM
authors.lastname: Carmo
authors.affiliation: Department of Rheumatology and Inflammation Research, The Sahlgren's Academy at University of Gothenburg, Sweden. Electronic address: maria.bokarewa@rheuma.gu.se.
authors.forename: Maria I
authors.initials: MI
authors.lastname: Bokarewa
keywords: Arthritis; CD5; S100A4; Src-tyrosine kinase; TCR; Th17 cell