Cholesterol and related sterols differentially modulate lipid domain dynamics in model membranes: A dual-probe...

The role of cholesterol in the organization and ordering of membrane domains has been well established over the past decades. However, the involvement of cholesterol precursors and byproduct sterols in modulating the physicochemical properties of cell membranes remains less thoroughly explored. In this study, we investigated the effects of cholesterol, two hydroxylated catabolites (24-hydroxycholesterol and 25-hydroxycholesterol), and two biosynthesis precursors (desmosterol and lanosterol) on model of liquid-ordered (Lo) and liquid-disordered (Ld) membrane domains. Membrane ordering and molecular mobility were assessed using two fluorescent probes; Laurdan, which senses polarity near the membrane aqueous interface and cholesterol-pyrene, which senses ordering closer to the center of the membrane bilayer. The results showed that Laurdan can distinguish between environmental polarity and the contribution of membrane domains. The probe mobility varied depending on the sterol and did not strictly correlate with membrane order. Cholesterol-pyrene revealed that the sterols induce varying degrees of ordering around the bilayer center. A notable observation in Ld membranes using different probes was that the ordering effect of sterols was similar near the lipid head groups and at the center of the bilayer. Hydroxycholesterols exhibited a low ordering effect, whereas cholesterol and desmosterol induced a strong effect. In contrast, in Lo membranes, hydroxycholesterols produced a strong ordering effect near the head groups but a reduced effect near the bilayer center.