Function: Adapter protein, which negatively regulates T-cell receptor (TCR) signaling. Inhibits T-cell antigen-receptor induced activation of nuclear factor of activated T-cells. Involved in the negative regulation of positive selection and mitosis of T-cells. May act by linking signaling proteins such as ZAP70 with CBL, leading to a CBL dependent degradation of signaling proteins. Tissue specificity: Expressed in lung and fetal brain. Weakly expressed in heart, adult brain, placenta, liver, skeletal muscle, kidney and pancreas. Similarity: Contains 1 SH2 domain. Contains 1 SH3 domain. Domain: The C-terminal domain is essential for the homodimerization and the interaction with CBL. While the interaction with CBL is apparently mediated via the hydrophobic region of this domain, the highly charged region is apparently required for the homodimerization.