FLVCR2 (MFSD7C) is a major facilitator superfamily transporter with dual functions in choline and heme homeostasis. As a choline uniporter, FLVCR2 mediates the majority of choline uptake across the blood-brain barrier from circulation into the brain 12, a process driven exclusively by the choline concentration gradient rather than proton coupling 3. Cryo-electron microscopy has resolved inward-facing and outward-facing conformations, revealing that conserved tryptophan and tyrosine residues form an aromatic cage for substrate binding 13. FLVCR2 also transports ethanolamine 3 and mediates choline export from brain lysophosphatidylcholine 2. Beyond the BBB, FLVCR2 enables apical choline uptake in intestinal epithelium 4. Additionally, FLVCR2 acts as a heme transporter required for mitochondrial respiration and thermogenesis regulation 5. At low heme levels, FLVCR2 interacts with electron transfer chain complexes and ATP2A2, promoting their ubiquitin-mediated degradation to inhibit thermogenesis; heme binding causes dissociation to allow ATP synthesis switching 5. Mutations in FLVCR2 cause Fowler syndrome (proliferative vasculopathy and hydranencephaly-hydrocephaly), characterized by impaired CNS vascular development, microcephaly, and embryonic lethality 6. FLVCR2 deficiency also exacerbates hemolytic-induced lung injury through ferroptosis 7.