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

• Published in: The Journal of biological chemistry Vol. 278; no. 1; pp. 208 - 218
• Main Authors: Gutiérrez-López, Marı́a Dolores, Ovalle, Susana, Yáñez-Mó, Marı́a, Sánchez-Sánchez, Noelia, Rubinstein, Eric, Olmo, Nieves, Lizarbe, Marı́a Antonia, Sánchez-Madrid, Francisco, Cabañas, Carlos
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 03.01.2003
• 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 β1 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 β1 integrins by temperature, divalent cation Mn2+, 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 β1 integrin subfamily we show that the expression of the PAINS-13 epitope depends on CD9 association with α6β1 integrin. The mAb PAINS-13 reactivity has been mapped to the CD9 region comprising residues 112–154 in the NH2 half of the large extracellular loop. Also, we show that the CD9 conformation recognized by mAb PAINS-13 is functionally relevant in β1 integrin-mediated cellular processes including wound healing migration, tubular morphogenesis, cell adhesion and spreading and in signal transduction involving phosphatidylinositol 3-kinase activation.