Sterol regulatory element-binding protein cleavage-activating protein (SCAP) is a escort protein required for cholesterol and lipid homeostasis []. It is an endoplasmic reticulum protein with eight transmembrane helices that serves as a cholesterol sensor []. In cholesterol-depleted cells, SCAP transports sterol regulatory element-binding proteins (SREBPs) to the Golgi, where the active fragment of SREBP is liberated by proteases so that it can activate genes for cholesterol synthesis [].A homologue of SCAP exists in Schizosaccharomyces pombe, named Scp1, which together with Sre1 (homologue to SREBP), may mediate a hypoxic response by monitoring oxygen-dependent sterol synthesis []..
SPRING1 is a glycosylated Golgi-resident membrane protein involved in SREBP signaling and cholesterol metabolism. It modulates the proper localization of SCAP (SREBP cleavage-activating protein) to the endoplasmic reticulum, thereby controlling the level of functional SCAP [].