TY - JOUR

T1 - Binding and intracellular transport of 25-hydroxycholesterol by Niemann-Pick C2 protein

AU - Petersen, Daniel

AU - Reinholdt, Peter

AU - Szomek, Maria

AU - Hansen, Selina Kruuse

AU - Poongavanam, Vasanthanathan

AU - Dupont, Alice

AU - Heegaard, Christian W.

AU - Krishnan, Kathiresan

AU - Fujiwara, Hideji

AU - Covey, Douglas F.

AU - Ory, Daniel S.

AU - Kongsted, Jacob

AU - Wüstner, Daniel

PY - 2020

Y1 - 2020

N2 - Side-chain oxidized cholesterol derivatives, like 25-hydroxycholesterol (25-OH-Chol) are important regulators of cellular cholesterol homeostasis. How transport of oxysterols through the endo-lysosomal pathway contributes to their biological function is not clear. The Niemann-Pick C2 protein (NPC2) is a small lysosomal sterol transfer protein required for export of cholesterol from late endosomes and lysosomes (LE/LYSs). Here, we show that 25-hydroxy-cholestatrienol, (25-OH-CTL), an intrinsically fluorescent analogue of 25-OH-Chol, becomes trapped in LE/LYSs of NPC2-deficient fibroblasts, but can efflux from the cells even in the absence of NPC2 upon removal of the sterol source. Fluorescence recovery after photobleaching (FRAP) of 25-OH-CTL in endo-lysosomes was rapid and extensive and only partially dependent on NPC2 function. Using quenching of NPC2's intrinsic fluorescence, we show that 25-OH-Chol and 25-OH-CTL can bind to NPC2 though with lower affinity compared to cholesterol and its fluorescent analogues, cholestatrienol (CTL) and dehydroergosterol (DHE). This is confirmed by calculations of binding energies which additionally show that 25-OH-CTL can bind in two orientations to NPC2, in stark contrast to cholesterol and its analogues. We conclude that NPC2's affinity for all sterols is energetically favored over their self-aggregation in the lysosomal lumen. Lysosomal export of 25-OH-Chol is not strictly dependent on the NPC2 protein.

AB - Side-chain oxidized cholesterol derivatives, like 25-hydroxycholesterol (25-OH-Chol) are important regulators of cellular cholesterol homeostasis. How transport of oxysterols through the endo-lysosomal pathway contributes to their biological function is not clear. The Niemann-Pick C2 protein (NPC2) is a small lysosomal sterol transfer protein required for export of cholesterol from late endosomes and lysosomes (LE/LYSs). Here, we show that 25-hydroxy-cholestatrienol, (25-OH-CTL), an intrinsically fluorescent analogue of 25-OH-Chol, becomes trapped in LE/LYSs of NPC2-deficient fibroblasts, but can efflux from the cells even in the absence of NPC2 upon removal of the sterol source. Fluorescence recovery after photobleaching (FRAP) of 25-OH-CTL in endo-lysosomes was rapid and extensive and only partially dependent on NPC2 function. Using quenching of NPC2's intrinsic fluorescence, we show that 25-OH-Chol and 25-OH-CTL can bind to NPC2 though with lower affinity compared to cholesterol and its fluorescent analogues, cholestatrienol (CTL) and dehydroergosterol (DHE). This is confirmed by calculations of binding energies which additionally show that 25-OH-CTL can bind in two orientations to NPC2, in stark contrast to cholesterol and its analogues. We conclude that NPC2's affinity for all sterols is energetically favored over their self-aggregation in the lysosomal lumen. Lysosomal export of 25-OH-Chol is not strictly dependent on the NPC2 protein.

KW - Binding

KW - Electronic structure calculation

KW - Fluorescence

KW - Free energy calculation

KW - Lysosome

UR - http://www.scopus.com/inward/record.url?scp=85075930997&partnerID=8YFLogxK

U2 - 10.1016/j.bbamem.2019.183063

DO - 10.1016/j.bbamem.2019.183063

M3 - Journal article

C2 - 31521631

AN - SCOPUS:85075930997

VL - 1862

JO - B B A - Biomembranes

JF - B B A - Biomembranes

SN - 0005-2736

IS - 2

M1 - 183063

ER -