STARD3
Description
The STARD3 (StAR related lipid transfer domain containing 3) is a protein-coding gene located on chromosome 17.
STARD3, also known as metastatic lymph node 64 protein (MLN64), is a late endosomal integral membrane protein involved in cholesterol transport. STARD3 creates membrane contact sites between the endoplasmic reticulum (ER) and late endosomes where it moves cholesterol. STARD3 forms a complex with STARD3NL (also known as MENTHO), and VAP proteins A and B (VAP-A, VAP-B) to tether the ER and late endosomes together. This interaction is regulated by phosphorylation of a serine in its FFAT motif. STARD3's closest homolog is StAR/StarD1, which initiates steroid production by moving cholesterol inside the mitochondrion.
STARD3 is a sterol-binding protein that primarily mediates cholesterol transport from the endoplasmic reticulum to endosomes. This transport mechanism is triggered by phosphorylation of the FFAT motif within STARD3, leading to membrane tethering between the endoplasmic reticulum and late endosomes through interactions with VAPA and VAPB. STARD3 functions as a lipid transfer protein, redirecting sterol to the endosome at the expense of the cell membrane, promoting membrane formation within endosomes. While STARD3 may also mediate cholesterol transport between other membranes, such as the mitochondrial or cell membrane, additional experimental evidence is needed to confirm this. STARD3 does not activate transcriptional cholesterol sensing. Furthermore, STARD3 can bind other lipids, such as lutein, a xanthophyll carotenoid that contributes to the macular pigment of the retina.
STARD3 is also known as CAB1, MLN64, es64.
