StAR Related Lipid Transfer Domain Containing Protein 6 (STARD6)

Cholesterol homeostasis is regulated, at least in part, by sterol regulatory element (SRE)-binding proteins and by liver X receptors. Upon sterol depletion, LXRs are inactive and SREBPs are cleaved, after which they bind promoter SREs and activate genes involved in cholesterol biosynthesis and uptake. Sterol transport is mediated by vesicles or by soluble protein carriers, such as steroidogenic acute regulatory protein (STAR). STAR is homologous to a family of proteins containing a 200- to 210-amino acid STAR-related lipid transfer (START) domain, including STARD6. The deduced 220-amino acid STARD6 protein is 26% and 32% identical to STARD4 and STARD5, respectively, and consists entirely of a START domain. Northern blot analysis revealed expression of a 1.5-kb transcript restricted to testis.