Heme is critical for a variety of cellular processes, but excess intracellular 
heme may result in oxidative stress and membrane injury. Feline leukemia virus 
subgroup C receptor (FLVCR1), a member of the SLC49 family of four paralogous 
genes, is a cell surface heme exporter, essential for erythropoiesis and 
systemic iron homeostasis. Disruption of FLVCR1 function blocks development of 
erythroid progenitors, likely due to heme toxicity. Mutations of SLC49A1 
encoding FLVCR1 are noted in patients with a rare neurodegenerative disorder: 
posterior column ataxia with retinitis pigmentosa. FLVCR2 is highly homologous 
to FLVCR1 and may function as a cellular heme importer. Mutations of SLC49A2 
encoding FLVCR2 are observed in Fowler syndrome, a rare proliferative vascular 
disorder of the brain. The functions of the remaining members of the SLC49 
family, MFSD7 and DIRC2 (encoded by the SLC49A3 and SLC49A4 genes), are unknown, 
although the latter is implicated in hereditary renal carcinomas. SLC48A1 (heme 
responsive gene-1, HRG-1), the sole member of the SLC48 family, is associated 
with the endosome and appears to transport heme from the endosome into the 
cytosol.