Figure 6.

CoQ₁₀ uptake and trafficking in mammalian cells. Dashed arrows indicate CoQ movement; solid arrows indicate chemical reactions. Proteins responsible for trafficking CoQ are identified where known; proteins mediating the transport shown by dashed arrows remain to be identified. (a) Exogenous CoQ uptake and intracellular CoQ distribution are mediated by several known mechanisms in mammalian cell culture. CD36 and NPC1L1 recognize and import exogenous CoQ within brown adipose tissue and small intestine epithelial cells, respectively. The endomembrane system facilitates intracellular trafficking of CoQ between membrane-bound vesicles. Dual-localized STARD7 in the mitochondria and cytosol support endogenous CoQ biosynthesis and distribution to the plasma membrane, respectively. (b) Model of lipoprotein-associated CoQ trafficking at the blood–brain barrier. SR-B1 and RAGE regulate influx of the HDL-associated CoQ across the blood–brain barrier, while LRP-1 regulates the efflux of LDL-associated CoQ. 1, receptor-mediated endocytosis; 2, recycling to apical side via the same receptor; 3, transcytosis to basolateral side; 4, transport to lysosome; 5, recycling or efflux of CoQ to apical membrane via LDL receptor family proteins; 6, paracellular transport detected due to defects in tight junctions. HDL, high-density lipoprotein; LDL, low-density lipoprotein. Created with BioRender.com (Accessed on 28 June 2023).