A Functionally Relevant Conformational Epitope on the CD9 Tetraspanin Depends on the Association with Activated β1Integrin

• Published in: The Journal of biological chemistry 2003-01, Vol.278 (1), p.208
• Main Authors: Marı́a Dolores Gutiérrez-López, Susana Ovalle, Marı́a Yáñez-MÃ, Noelia Sánchez-Sánchez, Eric Rubinstein, Nieves Olmo, Marı́a Antonia Lizarbe, Francisco Sánchez-Madrid, Carlos Cabañas
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M207805200

Tetraspanins associate on the cell membrane with several transmembrane proteins, including members of the integrin superfamily. The tetraspanin CD9 has been implicated in cell motility, metastasis, and sperm-egg fusion. In this study we characterize the first CD9 conformation-dependent epitope (detected by monoclonal antibody (mAb) PAINS-13) whose expression depends on changes in the activation state of associated β 1 integrins. MAb PAINS-13 precipitates CD9 under conditions that preserve the association of this tetraspanin with integrins, but not under conditions that disrupt these interactions. Induction of activation of β 1 integrins by temperature, divalent cation Mn 2+ , or mAb TS2/16 correlated with enhanced expression of the PAINS-13 epitope on a variety of cells. Through the use of different K562 myeloid leukemia transfectant cells expressing specific members of the β 1 integrin subfamily we show that the expression of the PAINS-13 epitope depends on CD9 association with α 6 β 1 integrin. The mAb PAINS-13 reactivity has been mapped to the CD9 region comprising residues 112–154 in the NH 2 half of the large extracellular loop. Also, we show that the CD9 conformation recognized by mAb PAINS-13 is functionally relevant in β 1 integrin-mediated cellular processes including wound healing migration, tubular morphogenesis, cell adhesion and spreading and in signal transduction involving phosphatidylinositol 3-kinase activation.