The N terminus of SKAP55 enables T cell adhesion to TCR and integrin ligands via distinct mechanisms

• Published in: The Journal of cell biology Vol. 203; no. 6; pp. 1021 - 1041
• Main Authors: Ophir, Michael J, Liu, Beiyun C, Bunnell, Stephen C
• Format: Journal Article
• Language: English
• Published: United States Rockefeller University Press 23.12.2013; The Rockefeller University Press
• Subjects: Adaptor Proteins, Signal Transducing - metabolism; Cell Adhesion; Cell adhesion & migration; Dimerization; Humans; Integrins - metabolism; Jurkat Cells; Ligands; Molecules; Phosphoproteins - chemistry; Phosphoproteins - metabolism; Phosphoproteins - physiology; Protein Structure, Tertiary; Proteins; Receptors, Antigen, T-Cell - metabolism; Signal Transduction; T cell receptors; T-Lymphocytes - cytology
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.201305088

The T cell receptor (TCR) triggers the assembly of "SLP-76 microclusters," which mediate signals required for T cell activation. In addition to regulating integrin activation, we show that Src kinase-associated phosphoprotein of 55 kD (SKAP55) is required for microcluster persistence and movement, junctional stabilization, and integrin-independent adhesion via the TCR. These functions require the dimerization of SKAP55 and its interaction with the adaptor adhesion and degranulation-promoting adaptor protein (ADAP). A "tandem dimer" containing two ADAP-binding SKAP55 Src homology 3 (SH3) domains stabilized SLP-76 microclusters and promoted T cell adhesion via the TCR, but could not support adhesion to integrin ligands. Finally, the SKAP55 dimerization motif (DM) enabled the coimmunoprecipitation of the Rap1-dependent integrin regulator Rap1-GTP-interacting adaptor molecule (RIAM), the recruitment of talin into TCR-induced adhesive junctions, and "inside-out" signaling to β1 integrins. Our data indicate that SKAP55 dimers stabilize SLP-76 microclusters, couple SLP-76 to the force-generating systems responsible for microcluster movement, and enable adhesion via the TCR by mechanisms independent of RIAM, talin, and β1 integrins.