p8I inhibits T cell receptor (TCR) signal transduction and NFAT activation: p8I is a proteolytic product of p12I in the ER membranes, the protein traffics to plasma membrane and localizes in the immunological synapse; p8I interacts with and inhibits the phosphorylation of the transmembrane protein called linker for activation of T cells (LAT) and by doing so, p8I disables LAT to transmit signals from TCR and to interact with other proteins, such as phospholipase C gamma 1, Vav proteins, and lymphocyte-specific protein tyrosine kinase (shown in red, cyan and green) on the TCR signaling pathway.