Ca2+ is a key second messenger in many intracellular signaling pathways. Stromal interaction molecule 1 (Stim1) is a ubiquitously expressed cell surface transmembrane glycoprotein that plays a role in medi-ating Ca2+ influx following the depletion of intracellular Ca2+ stores. STIM1 is a potential tumor suppressor; defects in STIM1 may cause rhabdomyosarcoma and rhabdoid tumors. Stim1 is implicated in tumor growth suppression and stromal-hematopoietic cell interactions.
