2Lomonosov Moscow State University, Biological Faculty, Department of Biochemistry, 119234 Moscow, Russia
3Lomonosov Moscow State University, Biological Faculty, Department of Biophysics, 119991 Moscow, Russia
* To whom correspondence should be addressed.
Received August 24, 2018; Revised September 13, 2018; Accepted September 13, 2018
Steroidogenesis takes place mainly in adrenal and gonadal cells that produce a variety of structurally similar hormones regulating numerous body functions. The rate-limiting stage of steroidogenesis is cholesterol delivery to the inner mitochondrial membrane, where it is converted by cytochrome P450scc into pregnenolone, a common precursor of all steroid hormones. The major role of supplying mitochondria with cholesterol belongs to steroidogenic acute regulatory protein (STARD1). STARD1, which is synthesized de novo as a precursor containing mitochondrial localization sequence and sterol-binding domain, significantly accelerates cholesterol transport and production of pregnenolone. Despite a tremendous interest in STARD1 fueled by its involvement in hereditary diseases and extensive efforts of numerous laboratories worldwide, many aspects of STARD1 structure, functioning, and regulation remain obscure and debatable. This review presents current concepts on the structure of STARD1 and other lipid transfer proteins, the role of STARD1 in steroidogenesis, and the mechanism of its functioning, as well as identifies the most controversial and least studied questions related to the activity of this protein.
KEY WORDS: cholesterol, lipid-binding proteins, protein structure, protein–protein interactions, steroidogenesis, phosphorylation, steroids