Interleukin-6 (IL-6) and/or Soluble IL-6 Receptor Down-regulation of Human Type II Collagen Gene Expression in Articular Chondrocytes Requires a Decrease of Sp1·Sp3 Ratio and of the Binding Activity of Both Factors to the COL2A1 Promoter

Benoît Porée (1) , Magdalini Kypriotou (1) , Christos Chadjichristos (1) , Gallic Beauchef (1) , Emmanuelle Renard (1) , Florence Legendre (1) , Martine Melin (2, 3) , Sylviane Gueret (3, 2) , Daniel-Jean Hartmann (2, 3) , Frédéric Malléin-Gerin (4) , Jean-Pierre Pujol (1) , Karim Boumediene (1) , Philippe Galéra (1)

1 Matrice extracellulaire normale et pathologique
2 NOVOTEC
3 LMI - Laboratoire des Multimatériaux et Interfaces
4 IBCP - Institut de biologie et chimie des protéines [Lyon]

Type II collagen is composed of alpha1(II) chains encoded by the COL2A1 gene. Alteration of this cartilage marker is a common feature of osteoarthritis. Interleukin-6 (IL-6) is a pro-inflammatory cytokine that needs a soluble form of receptor called sIL-6R to exert its effects in some cellular models. In that case, sIL-6R exerts agonistic action. This mechanism can make up for the partial or total absence of membrane-anchored IL-6 receptors in some cell types, such as chondrocytes. Our study shows that IL-6, sIL-6R, or both inhibit type II collagen production by rabbit articular chondrocytes through a transcriptional control. The cytokine and/or sIL-6R repress COL2A1 transcription by a -63/-35 sequence that binds Sp1.Sp3. Indeed, IL-6 and/or sIL-6R inhibit Sp1 and Sp3 expression and their binding activity to the 63-bp promoter. In chromatin immunoprecipitation experiments, IL-6.sIL-6R induced an increase in Sp3 recruitment to the detriment of Sp1. Knockdown of Sp1.Sp3 by small interference RNA and decoy strategies were found to prevent the IL-6- and/or sIL-6R-induced inhibition of COL2A1 transcription, indicating that each of these Sp proteins is required for down-regulation of the target gene and that a heterotypic Sp1.Sp3 complex is involved. Additionally, Sp1 was shown to interact with Sp3 and HDAC1. Indeed, overexpression of a full-length Sp3 cDNA blocked the Sp1 up-regulation of the 63-bp COL2A1 promoter activity, and by itself, inhibits COL2A1 transcription. We can conclude that IL-6, sIL-6R, or both in combination decrease both the Sp1.Sp3 ratio and DNA-binding activities, thus inhibiting COL2A1 transcription.

Domaines: Rhumatologie et système ostéo-articulaire; Génomique, Transcriptomique et Protéomique [q-bio.GN]

Benoît Porée, Magdalini Kypriotou, Christos Chadjichristos, Gallic Beauchef, Emmanuelle Renard, et al.. Interleukin-6 (IL-6) and/or Soluble IL-6 Receptor Down-regulation of Human Type II Collagen Gene Expression in Articular Chondrocytes Requires a Decrease of Sp1·Sp3 Ratio and of the Binding Activity of Both Factors to the COL2A1 Promoter. Journal of Biological Chemistry, 2008, 283 (8), pp.4850-4865. ⟨10.1074/jbc.M706387200⟩. ⟨hal-03838464⟩