FLVCR1
Developmental stage
Isoform 1
Down-regulated in haemopoietic progenitor cells undergoing differentiation and hemoglobinization. Abundant in fetal liver.
Function
Uniporter that mediates the transport of extracellular choline and ethanolamine into cells, thereby playing a key role in phospholipid biosynthesis (PubMed:37100056, PubMed:38693265, PubMed:38778100). Choline and ethanolamine are the precursors of phosphatidylcholine and phosphatidylethanolamine, respectively, the two most abundant phospholipids (PubMed:38693265, PubMed:38778100). Transport is not coupled with proton transport and is exclusively driven by the choline (or ethanolamine) gradient across the plasma membrane (PubMed:38693265, PubMed:38778100). Also acts as a heme b transporter that mediates heme efflux from the cytoplasm to the extracellular compartment (PubMed:15369674, PubMed:20610401, PubMed:22483575, PubMed:23187127, PubMed:27923065).
Isoform 1
Uniporter that mediates the transport of extracellular choline and ethanolamine into cells (PubMed:37100056, PubMed:38693265). Choline and ethanolamine are the precursors of phosphatidylcholine and phosphatidylethanolamine, respectively, the two most abundant phospholipids (PubMed:38693265). Transport is not coupled with proton transport and is exclusively driven by the choline (or ethanolamine) gradient across the plasma membrane (PubMed:38693265). Also acts as a heme b transporter that mediates heme efflux from the cytoplasm to the extracellular compartment (PubMed:15369674, PubMed:20610401, PubMed:22483575, PubMed:23187127, PubMed:27923065). Heme export depends on the presence of HPX and is required to maintain intracellular free heme balance, protecting cells from heme toxicity (PubMed:20610401). Heme export provides protection from heme or ferrous iron toxicities in liver, brain, sensory neurons and during erythropoiesis, a process in which heme synthesis intensifies (PubMed:20610401, PubMed:23187127). Possibly export coproporphyrin and protoporphyrin IX, which are both intermediate products in the heme biosynthetic pathway (PubMed:20610401). Does not export bilirubin (PubMed:20610401). The molecular mechanism of heme transport, whether electrogenic, electroneutral or coupled to other ions, remains to be elucidated (PubMed:20610401, PubMed:23187127).
Isoform 2
Heme b transporter that promotes heme efflux from the mitochondrion to the cytoplasm. Essential for erythroid differentiation.
Isoform 1
(Microbial infection) Confers susceptibility to feline leukemia virus subgroup C (FeLV-C) infection in vitro.
Involvement in disease
Posterior column ataxia with retinitis pigmentosa
PCARP
A neurodegenerative syndrome beginning in infancy with areflexia and retinitis pigmentosa. Nyctalopia (night blindness) and peripheral visual field loss are usually evident during late childhood or teenage years, with subsequent progressive constriction of the visual fields and loss of central retinal function over time. A sensory ataxia caused by degeneration of the posterior columns of the spinal cord results in a loss of proprioceptive sensation that is clinically evident in the second decade of life and gradually progresses. Scoliosis, camptodactyly, achalasia, gastrointestinal dysmotility, and a sensory peripheral neuropathy are variable features of the disease. Affected individuals have no clinical or radiological evidence of cerebral or cerebellar involvement.
None
The disease is caused by variants affecting the gene represented in this entry. Defective neuronal heme transmembrane export due to FLVCR1 mutations may abrogate the neuroprotective effects of neuroglobin and initiate an apoptotic cascade that results in the selective degeneration of photoreceptors in the neurosensory retina and sensory neurons in the posterior spinal cord.
Defects in FLVCR1 are a cause of a sensory neuropathy resulting in pain insensitivity. Patients have decreased sensing of pain, temperature and touch. Self-injury, ulcers and amputations are commonly observed in affected individuals.
Post-translational modifications
N-Glycosylated.
Sequence Similarities
Belongs to the major facilitator superfamily. Feline leukemia virus subgroup C receptor (TC 2.A.1.28.1) family.
Tissue Specificity
Found all hematopoietic tissues including peripheral blood lymphocytes. Some expression is found in pancreas and kidney.
Cellular localization
- Isoform 1
- Cell membrane
- Multi-pass membrane protein
- Isoform 2
- Mitochondrion membrane
- Multi-pass membrane protein
Alternative names
FLVCR, FLVCR1, Choline/ethanolamine transporter FLVCR1, Feline leukemia virus subgroup C receptor-related protein 1, Heme transporter FLVCR1, Feline leukemia virus subgroup C receptor, hFLVCR