Orthogonal lipid sensors identify transbilayer asymmetry of plasma membrane cholesterol

• Published in: Nature chemical biology Vol. 13; no. 3; pp. 268 - 274
• Main Authors: Liu, Shu-Lin, Sheng, Ren, Jung, Jae Hun, Wang, Li, Stec, Ewa, O'Connor, Matthew J, Song, Seohyoen, Bikkavilli, Rama Kamesh, Winn, Robert A, Lee, Daesung, Baek, Kwanghee, Ueda, Kazumitsu, Levitan, Irena, Kim, Kwang-Pyo, Cho, Wonhwa
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.03.2017; Nature Publishing Group
• Subjects: 631/80/86; 631/92/287; 631/92/314; 631/92/96; Asymmetry; Biochemical Engineering; Biochemistry; Bioorganic Chemistry; Cell Biology; Cell Line; Cell Membrane - chemistry; Chemistry; Chemistry/Food Science; Cholesterol; Cholesterol - analysis; HEK293 Cells; Homeostasis; Humans; Hyperlipidemia; Lipids; Lipids - chemistry; Membranes; Sensors; United States > US; Illinois; Chicago Illinois
• ISSN: 1552-4450; 1552-4469
• DOI: 10.1038/nchembio.2268

Orthogonal cholesterol sensors that are useful for imaging cholesterol in the plasma membrane leaflets reveal an asymmetry in which a high outer leaflet concentration is important for signaling processes and is potentially actively maintained. Controlled distribution of lipids across various cell membranes is crucial for cell homeostasis and regulation. We developed an imaging method that allows simultaneous in situ quantification of cholesterol in two leaflets of the plasma membrane (PM) using tunable orthogonal cholesterol sensors. Our imaging revealed marked transbilayer asymmetry of PM cholesterol (TAPMC) in various mammalian cells, with the concentration in the inner leaflet (IPM) being ∼12-fold lower than that in the outer leaflet (OPM). The asymmetry was maintained by active transport of cholesterol from IPM to OPM and its chemical retention at OPM. Furthermore, the increase in the IPM cholesterol level was triggered in a stimulus-specific manner, allowing cholesterol to serve as a signaling lipid. We found excellent correlation between the IPM cholesterol level and cellular Wnt signaling activity, suggesting that TAPMC and stimulus-induced PM cholesterol redistribution are crucial for tight regulation of cellular processes under physiological conditions.