StAR-related lipid transfer protein 3

Sterol-binding protein that mediates cholesterol transport from the endoplasmic reticulum to endosomes. Creates contact site between the endoplasmic reticulum and late endosomes: localizes to late endosome membranes and contacts the endoplasmic reticulum via interaction with VAPA and VAPB. 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. May also mediate cholesterol transport between other membranes, such as mitochondria membrane or cell membrane. However, such results need additional experimental evidences; probably mainly mediates cholesterol transport from the endoplasmic reticulum to endosomes. Does not activate transcriptional cholesterol sensing. Able to bind other lipids, such as lutein, a xanthophyll carotenoids that form the macular pigment of the retina.