Sterol-binding protein that mediates cholesterol transport from the endoplasmic reticulum to endosomes (PubMed:11053434, PubMed:15930133, PubMed:22514632, PubMed:28377464, PubMed:33124732). The sterol transport mechanism is triggered by phosphorylation of FFAT motif that leads to membrane tethering between the endoplasmic reticulum and late endosomes via interaction with VAPA and VAPB (PubMed:24105263, PubMed:28377464, PubMed:33124732). Acts as a lipid transfer protein that redirects sterol to the endosome at the expense of the cell membrane and favors membrane formation inside endosomes (PubMed:28377464). May also mediate cholesterol transport between other membranes, such as mitochondria membrane or cell membrane (PubMed:12070139, PubMed:19965586). However, such results need additional experimental evidences; probably mainly mediates cholesterol transport from the endoplasmic reticulum to endosomes (PubMed:28377464). Does not activate transcriptional cholesterol sensing (PubMed:28377464). Able to bind other lipids, such as lutein, a xanthophyll carotenoids that form the macular pigment of the retina (PubMed:21322544). {ECO:0000269|PubMed:11053434, ECO:0000269|PubMed:12070139, ECO:0000269|PubMed:15930133, ECO:0000269|PubMed:19965586, ECO:0000269|PubMed:21322544, ECO:0000269|PubMed:22514632, ECO:0000269|PubMed:24105263, ECO:0000269|PubMed:28377464, ECO:0000269|PubMed:33124732}. This is the function of STARD3 (StAR related lipid transfer domain containing 3, Ensembl gene identifier ENSG00000131748).