Signaling threshold-regulating transmembrane adaptor 1 (SIT1)

Signaling threshold-regulating transmembrane adaptor 1 (SIT1) is a transmembrane adaptor protein that regulates T-cell receptor (TCR)-mediated signaling, serving as a negative modulator of T-cell activation, proliferation, and tolerance. SIT1 is essential for proper thymocyte selection and peripheral T-cell homeostasis. Loss of SIT1 leads to enhanced TCR signaling, increased T-cell activation, and a predisposition to autoimmunity in experimental models. Mechanistically, SIT1 negatively regulates several signaling pathways downstream of TCR stimulation, including the PI3K-Akt and Foxo1 pathways, and may function by interacting with signal transducers such as Grb2 and SHP2. SIT1 is predominantly classified as a scaffold/adaptor protein rather than a classical receptor, enzyme, or ion channel, and is primarily studied in the context of immune cell biology rather than as a direct therapeutic target[1][2][3][6].

Other names

SITSHP2-interacting transmembrane adaptor proteinSuppression-inducing transmembrane adaptor 1gp30/40SHP2 interacting transmembrane adaptorSIT-RSHP-2 interacting transmembrane adaptor protein