Research ArticleTCR Signaling

RIAM Regulates the Cytoskeletal Distribution and Activation of PLC-γ1 in T Cells

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Science Signaling  01 Dec 2009:
Vol. 2, Issue 99, pp. ra79
DOI: 10.1126/scisignal.2000409

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Dual Nature of RIAM

Activation of T cells involves not only signaling downstream of the T cell receptor (TCR), but also activation of and signaling by integrins. The adaptor protein Rap1–guanosine triphosphate (GTP)–interacting adaptor molecule (RIAM) mediates inside-out activation of integrins in lymphocytes and participates in reorganization of the actin cytoskeleton. RIAM is also recruited to the interface between the T cell and an antigen-presenting cell; therefore, Patsoukis et al. investigated whether RIAM participated in the TCR signaling events that contribute to T cell activation. They found that RIAM bound to phospholipase C–γ1 (PLC-γ1) and, through interactions with the actin cytoskeleton, regulated the localization of PLC-γ1, resulting in the production of inositol trisphophate (IP3) and diacylglycerol. Knockdown of RIAM in T cells resulted in defective activation of PLC-γ1, diminished mobilization of Ca2+, and impaired translocation of the transcription factor NFAT to the nucleus in response to stimulation of the TCR. Thus, RIAM has multiple functions in T cell activation, regulating Ca2+ signaling and gene expression downstream of the TCR, integrin activity, and the actin cytoskeleton.

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