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. Author manuscript; available in PMC: 2010 Jan 1.
Published in final edited form as: Annu Rev Immunol. 2009;27:591–619. doi: 10.1146/annurev.immunol.021908.132706

Figure 2. A model of integrin activation.

Figure 2

Upon TCR ligation, the LAT/SLP-76-nucleated signalosome assembles. This complex allows for the activation of three pathways necessary for inside-out activation of integrins. Vav1 and Itk contribute to the actin reorganization required for integrin mobility (pathway A). Mobilization of the ADAP/SKAP-55/RIAM complex is necessary for activated Rap1 plasma membrane localization (pathway B). An active Rap1/RIAM complex induces the association of talin with integrin β tails, perhaps resulting in altered integrin affinity. Thirdly, PLCγ1-mediated activation of DAG leads to PKD1 activation and association with Rap1 (pathway C). This interaction is required for Rap1 activation and contributes to Rap1 recruitment. Rap1 in turn recruits RAPL, and subsequent RAPL binding to αL subunits results in integrin clustering and affinity changes.