Fig. 6: RMDN3 TPR domain binds and transfers lipid radicals.

a Schematic of the liposome assay to monitor lipid radical transfer activity. b RMDN3 shows higher lipid transfer activity in the presence of lipid radicals. The y‐axes in the graphs show the percentage of acceptor liposome fluorescence, which was calculated using the following formula: 100×Facceptor /(Facceptor+Fdonor). c Liposome assay to measure lipid radicals transfer by RMDN3 TPR. Donor liposome (containing biotinyl-cap lipids and unsaturated lipids), which bind to streptavidin magnetic beads, were treated with or without AAPH (500 µM), a radical inducer. After washed out AAPH, acceptor liposomes and RMDN3 TPR were mixed with donor liposome-bead lysates. LipiRADICAL Green was then added to the mixture. After removing donor liposome-bead by binding to magnetic racks, the supernatant (including acceptor liposomes and RMDN3 TPR mixture) LipiRADICAL Green fluorescence signals were measured. d The RMDN3 TPR binds and transfers lipid radicals. The donor liposome (containing biotinyl-cap lipids and unsaturated lipids), which bind streptavidin magnetic beads, lysates were treated with or without AAPH (500 µM), a radical inducer. After washed out AAPH, acceptor liposomes and RMDN3 TPR or RMDN3 TPR alone were mixed with donor liposome-bead lysates. Then, LipiRADICAL Green was added to the mixture. After removing donor liposome-bead by binding to magnetic racks, the supernatant (including acceptor liposomes and RMDN3 TPR or RMDN3 TPR alone) LipiRADICAL Green fluorescence signals were measured. e Schematic illustration: induction of mitochondrial ROS promotes MERC formation, and RMDN3 transfers lipid radicals from mitochondria to the ER at MERCs to attenuate mitochondrial oxidative stress. Data are mean ± s.e.m. (n = 3, triplicate), and statistical significance was analyzed by one-way analysis of variance (ANOVA) (b–d). P values are indicated as ****p < 0.0001.