FLVCR2

Feline leukemia virus subgroup C cellular receptor family, member 2 is a choline transporter belonging to the major facilitator superfamily. It is a uniporter transmembrane protein that transports choline across the plasma membrane via a concentration gradient. FLVCR2 is highly enriched in endothelial cells of the blood-brain barrier but is also expressed in peripheral tissues such as the small intestine where it absorbs dietary choline. At the blood-brain barrier, FLVCR2 is the primary transporter of choline responsible for approximately 60% of the brains supply.
Mutations in FLVCR2 have been associated with proliferative vasculopathy and hydranencephaly-hydrocephaly syndrome.

Discovery

In 2009, the feline FLVCR2 ortholog was the first identified as a receptor of the Feline leukemia virus in cats. The following year, it was characterised as a heme transporter as it was shown to bind heme, increase heme transport. However, in 2024 it was shown to transport choline both in vivo and in vitro through the use of radiolabel choline transport assays and structural characterisation showing choline bound. FLVCR2's role in disease and interactions with heme remains an ongoing investigation.

Structure

FLVCR2 adopts the canonical MFS fold consisting of 12 transmembrane alpha-helices. It is a 60 kDa protein with no significant extracellular structures or glycosylation.