This entry includes TESPA1, ITPRID1 (also known CCDC129) and ITPRID2 (also known as SSFA2). SSFA2, also known as Ki-ras-induced actin-interacting protein (KRAP), interacts with inositol 1,4,5-trisphosphate receptor (IP3R, also known as ITPR) []. SSFA2 was first localised as a membrane-bound form with extracellular regions suggesting it might be involved in the regulation of filamentous actin and signals from the outside of the cells []. It has now been shown to be critical for the proper subcellular localisation and function of IP3R. Inositol 1,4,5-trisphosphate receptor functions as the Ca2+ release channel on specialised endoplasmic reticulum membranes, so the subcellular localisation of IP3R is crucial for its proper function [].TESPA1 (Thymocyte-expressed positive selection-associated protein 1) is required for the development and maturation of T-cells, its function being essential for the late stages of thymocyte development. It plays a role in T-cell antigen receptor (TCR)-mediated activation of the ERK and NFAT signaling pathways, possibly by serving as a scaffolding protein that promotes the assembly of the LAT signalosome in thymocytes []. TESPA1 shows sequence homology to SSFA2 and physically associates with IP3R in T and B lymphocytes [].The function of ITPRID1 is not clear.
