Lipid-binding START domain of mammalian STARD10 and related proteins
This subfamily includes the steroidogenic acute regulatory protein (StAR)-related lipid transfer (START) domains of mammalian STARD10 (also known as CGI-52, PTCP-like, and SDCCAG28). The START domain family belongs to the SRPBCC (START/RHO_alpha_C/PITP/Bet_v1/CoxG/CalC) domain superfamily of proteins that bind hydrophobic ligands. SRPBCC domains have a deep hydrophobic ligand-binding pocket. STARD10 binds phophatidylcholine and phosphatidylethanolamine. This protein is widely expressed and is synthesized constitutively in many organs. It may function in the liver in the export of phospholipids into bile. It is concentrated in the sperm flagellum, and may play a role in energy metabolism. In the mammary gland it may participate in the enrichment of lipids in milk, and be a potential marker of differentiation. Its expression is induced in this gland during gestation and lactation. It is overexpressed in mammary tumors from Neu/ErbB2 transgenic mice, in several breast carcinoma cell lines, and in 35% of primary human breast cancers, and may cooperate with c-erbB receptor signaling in breast oncogenesis. It is a potential marker of disease outcome in breast cancer; loss of STARD10 expression in breast cancer strongly predicts an aggressive disease course. The lipid transfer activity of STRAD10 is downregulated by phosphorylation of its Ser284 by CK2 (casein kinase 2).