FLVCR2

Summary: Endogenous human imaging supports an ER-associated pool without resolving its bilayer.

Reason: PMID:32973183 Results and supplementary Figure 10d/e support a fraction of endogenous human THP-1 FLVCR2 at ER-mitochondrial junctions, with ER-marker overlap and separate SERCA2b association experiments. This is not inferred merely because an interaction partner is an ER protein. Retain the experimental ER-associated location as non-core while preserving the contact-site resolution limit: these images do not independently resolve insertion into the ER bilayer. Mouse-brain fractionation and murine tagged-protein experiments are kept distinct from the endogenous human imaging.

Summary: The mapped ER-associated pool is contextual, with contact-site resolution limits.

Reason: The UniProt subcellular-location mapping is supported by the contextual organellar localization study PMID:32973183. Actual supplementary Figure 10 shows endogenous human THP-1 FLVCR2 colocalizing with an ER marker and SERCA2b at ER-mitochondrial contacts; the source also reports predominant mitochondrial localization. Retain the curator-supported ER-associated pool as non-core, with the explicit limit that diffraction-limited colocalization does not determine which bilayer contains FLVCR2 at a contact. Do not turn this into a claim that every FLVCR2 product is an ER transporter.

Summary: Independent human surface assays support the term; the older source-specific experiment is unverified.

Reason: The source-specific plasma-membrane EXP annotation is retained with explicit access limits: PMID:14729055 was verified in official metadata and its abstract read, but full text was unavailable, so the exact original localization experiment is not independently verified here. Human FLVCR2 surface localization is independently supported by PMID:38302740 and by membrane-GFP colocalization and transport experiments in PMID:38778100. The broad location is a core feature of the amine transporter; no calcium-chelate activity, pituitary-specific assay detail or splice-product function is inferred from the older abstract.

Summary: Human surface localization supports the plasma-membrane transport core.

Reason: PMID:38302740 reports human FLVCR2 plasma-membrane localization in its transport/mutant experiments and distinguishes S203Y loss of uptake from reduced abundance or defective surface localization. Cellular uptake/washout provide functional corroboration. Retain the core location without transferring mouse brain observations or full-length localization to every product.

Summary: Human FLVCR2 colocalizes with a plasma-membrane marker in transport-assay cells.

Reason: PMID:38778100 colocalizes expressed human FLVCR2 with membrane-targeted GFP in HEK293 cells and supplies immunostaining Methods and cellular transport assays. Retain plasma membrane as core, distinguishing the human full-length construct from FLVCR1 and the natural 321-residue product.

Summary: Composite localization inference agrees with independent human surface assays.

Reason: The composite subcellular-location/orthology mapping agrees with direct human FLVCR2 plasma-membrane imaging and transport in PMID:38302740 and PMID:38778100. The mouse donor Q91X85 identity is verified. Retain the core location without treating the mapping as an independent experiment or assuming the short product shares it.

Summary: Human FLVCR2 mediates cellular choline uptake, release and yeast complementation.

Reason: PMID:38302740 assays human FLVCR2 in HEK293 cells with empty-vector, CHT1 and S203Y controls, and separately demonstrates human-protein rescue of choline uptake in yeast Hnm1 knockout cells. Dose/time dependence, sodium replacement and choline release support facilitative transport. CHKA/CHAT co-expression enhances metabolic trapping; this is cellular accumulation, not purified-protein reconstitution. Preserve the supported plasma-membrane extension.

Summary: Human uptake, washout, structure and mutagenesis support choline transport.

Reason: PMID:38778100 measures human FLVCR2-dependent radiolabeled choline uptake, dose/time curves, transport-site mutants and separate choline washout in HEK293 cells. CHKA enhances accumulation; the same paper independently resolves choline-bound human FLVCR2. Retain core transport while separating cellular uptake from structural binding and from FLVCR1 experiments.

Summary: Choline transport is independently established; this source-specific assay remains unverified.

Reason: Independent human FLVCR2 assays in PMID:38302740 and PMID:38778100 establish the core choline-transporter activity. Retain this experimental assertion at term level, preserving PMID:40972734 as its original reference. Authentic metadata/abstract for PMID:40972734 were recovered, but its exact FLVCR2 assay remains UNVERIFIED; do not infer a wrong gene or transfer another SLC's kinetics.

Summary: Combined electronic inference agrees with demonstrated human choline transport.

Reason: The composite ARBA/orthology assignment agrees with direct human FLVCR2 choline uptake and release in PMID:38302740 and PMID:38778100. Q91X85 is verified mouse Flvcr2 with experimental transporter annotations. Retain the core activity without counting the electronic mapping as another experiment or transferring full-length function to the short product.

Summary: Target-specific uptake evidence supports non-core heme activity despite unresolved mechanistic confirmation.

Reason: The heme-transporter IBD at PTN000858905 lies on the verified human FLVCR2 path and has target-specific experimental grounding. PMID:20823265 reports increased ZnMP accumulation in human-FLVCR2-expressing CHO cells, increased 55Fe-hemin accumulation in Xenopus oocytes expressing human FLVCR2, and reduced ZnMP uptake after two independent siRNAs in human TE671 cells. These convergent cellular observations support retaining the broad heme-transport assertion as non-core. PMID:38778100 explicitly questions confirmation of the earlier uptake interpretation and supplies stronger structural and functional evidence for choline and ethanolamine as primary substrates. Its W102-centred amine recognition and Q191A transport assays test those amines, however, not heme flux or exclusion. KEEP_AS_NON_CORE is preferred to MARK_AS_OVER_ANNOTATED because the actual target-specific uptake and perturbation results remain positive and have not been directly contradicted by the inspected assays. They do not establish purified full-length heme translocation, its mechanism or its physiological importance.

Summary: Cellular heme-uptake evidence is retained outside the better-established amine-transport core.

Reason: PMID:20823265 tested human FLVCR2 in several settings: expression increased ZnMP accumulation in CHO cells and 55Fe-hemin accumulation in Xenopus oocytes, while two FLVCR2 siRNAs reduced ZnMP uptake in human TE671 cells. These are cellular accumulation and perturbation assays, not purified-transporter flux measurements; binding and toxicity alone would not establish transport. PMID:38778100 describes the heme-uptake interpretation as unconfirmed and establishes an amine-binding pocket with choline/ethanolamine transport-site mutants. That is a substantive reason to keep heme outside the principal amine-transport core, but its inspected amine assays do not demonstrate absent heme flux, and the paper also acknowledges transporter substrate promiscuity. KEEP_AS_NON_CORE is preferred to MARK_AS_OVER_ANNOTATED because it gives weight to the complementary target-specific uptake experiments while restricting their mechanistic and physiological interpretation. The current evidence does not establish that the original broad activity assertion is excessive. No heme-export capacity follows.

Summary: Human FLVCR2 itself performs the measured choline movement.

Reason: PMID:38302740 directly establishes human FLVCR2-dependent cellular choline uptake, human-protein yeast complementation and release from preloaded cells. Retain core choline transport on these assays, separately from mouse brain-metabolite phenotypes and kinase-assisted trapping. The transporter performs movement rather than merely being necessary for a downstream outcome.

Summary: Cellular uptake and washout establish choline transport, distinct from phosphorylation.

Reason: Human FLVCR2 choline accumulation and separate washout in PMID:38778100 support the core transport process, with structural/mutational support for substrate recognition. CHKA changes cellular trapping and performs phosphorylation itself. Choline bidirectionality does not establish heme direction or universal tissue direction.

Summary: The transport process is independently supported despite unresolved exact-source access.

Reason: Retain the PMID:40972734 choline-transport assertion at term level using independently established human FLVCR2 transport in PMID:38302740 and PMID:38778100. Exact source-specific PMID:40972734 experimental support remains UNVERIFIED because access was abstract-only. Preserve the original citation without inventing assay details or importing other transporter measurements.

Summary: Mouse-derived choline transport agrees with direct human-protein assays.

Reason: The Ensembl transfer from verified mouse Flvcr2 is concordant with direct human choline uptake and release in PMID:38302740 and PMID:38778100. The donor has experimental process support rather than only propagated records. Retain core choline transport performed by the transporter itself; no synthesis-enzyme activity or short-product function follows.

Summary: Verified broad membrane propagation is less informative than plasma membrane.

Reason: The membrane IBD at PTN000858822 (Eukaryota) lies on the exact human FLVCR2 target path, and the normal PAINT slice matches the original GAF. Its broad location is sound, but the plasma-membrane annotation is more specific and directly corroborated by human FLVCR2 colocalization with membrane GFP and surface transport assays in PMID:38778100. Official plasma-membrane ancestry includes GO:0016020. The target appearing among its own sources is expected experimental grounding and is not circularity; neither donor count nor paralog identity is used to dismiss the IBA.

Summary: Independent human binding assays support the non-core ancestral binding assertion.

Reason: The PTN000858905 heme-binding IBD and its descent to human FLVCR2 are verified against the original GAF and family tree. PMID:20823265 reports hemin-agarose association of human FLVCR2 from cell lysates with soluble-hemin competition; PMID:32973183 independently measures heme binding by the purified human N-terminal fragment, residues 1–84. These are positive binding observations distinct from the disputed interpretation of cellular heme transport. The small-amine site characterized in PMID:38778100 does not test or exclude the separate N-terminal heme interaction. Retain binding as non-core rather than mark it over-annotated: it has direct target-specific support, but establishes neither a principal physiological substrate nor a transport direction.

Summary: Hemin-agarose association supports contextual binding in human-protein lysates.

Reason: In PMID:20823265, HA-tagged human FLVCR2 from CHO lysates associated with hemin-agarose, whereas the feline thiamine-transporter control did not, and soluble hemin reduced the association. This supports the binding annotation within the lysate-pulldown scope, not a purified full-length affinity measurement. Purified human N-terminal binding in PMID:32973183 supplies independent corroboration. PMID:38778100 questions heme-transport confirmation, but its amine-pocket experiments do not negate these binding observations or assay the N-terminal interaction. KEEP_AS_NON_CORE is justified by positive binding evidence while its physiological role remains unresolved; binding must not be treated as proof of heme flux.

Summary: A purified human N-terminal fragment binds heme; natural short-product function is unresolved.

Reason: PMID:32973183 directly assays the purified human FLVCR2 N-terminal fragment, residues 1–84, by heme co-elution and optical titration; histidine substitutions disrupt the response. This is target-specific binding evidence, distinct from murine full-length constructs used in several cellular experiments. PMID:38778100 establishes small-amine coordination in the transmembrane pocket and questions confirmation of heme transport, but it does not test or exclude this separate N-terminal binding site. Retain the measured binding as non-core rather than mark it over-annotated; neither a central physiological heme role nor heme translocation is established by the fragment assay. The engineered deletion and the 84-residue fragment are not the natural 321-residue splice product, which must not inherit this binding claim without evidence.

Summary: Substrate-specific transport activities make this molecular-function parent too general.

Reason: The InterPro transmembrane-transporter assignment is consistent with FLVCR2 architecture and direct assays on the human protein. PMID:38302740 demonstrates human FLVCR2-dependent choline uptake and release in HEK293 cells; PMID:38778100 independently supports choline and ethanolamine transport. The retained substrate-specific molecular functions GO:0015220 and GO:0034228 are official descendants of GO:0022857, so this broad molecular-function assertion is redundant rather than biologically false.

Summary: Endogenous human imaging supports mitochondrial association with unresolved inner-versus-outer location.

Reason: PMID:32973183 measures endogenous human THP-1 FLVCR2 colocalization with MitoTracker and reports no staining in knockout controls; mouse-brain fractionation and murine MFSD7C-GFP expressed in human cells provide distinct corroborating observations. Retain the mitochondrial-membrane location as non-core. The authors explicitly state that the inner versus outer membrane is unknown, and their Figure6 panels are alternative models rather than localization experiments. No function or localization is assigned to the 321-residue natural product from an engineered deletion.

Summary: A contextual mitochondrial pool supports the broad mapping, not a membrane-subcompartment claim.

Reason: The UniProt mitochondrial-membrane mapping is consistent with the experimentally observed organellar pool in PMID:32973183: endogenous human THP-1 FLVCR2 colocalization with MitoTracker is supported by antibody-specificity controls, separately from mouse-brain enrichment and murine tagged-protein localization. Keep this contextual location outside the plasma-membrane amine-transport core. The paper explicitly leaves inner versus outer membrane unresolved, so the existing broad mitochondrial-membrane term is retained without sharpening it.

Summary: Human structural evidence corroborates mouse-derived choline recognition.

Reason: Verified mouse Flvcr2 Q91X85 carries experimental choline-binding evidence. Independent human FLVCR2 choline-bound structures, ligand-dependent fluorescence and transport-site mutagenesis in PMID:38778100 directly corroborate substrate recognition. Retain as non-core because binding is subsidiary to the more informative transport activity, not a separate established choline-sensor function or a property assigned to all products.

Summary: Human FLVCR2 ethanolamine uptake supports a second core transport activity.

Reason: PMID:38778100 directly measures human FLVCR2-dependent ethanolamine uptake in HEK293 cells with dose/time dependence and site mutants. ETNK1 does not substantially boost FLVCR2 uptake in that study, whereas PMID:38302740 reports positive kinase-assisted uptake after a negative unassisted condition. Retain a second core transport activity with assay-condition limits. The ethanolamine-bound structure and specifically reported ethanolamine washout in PMID:38778100 concern FLVCR1 and are not transferred to FLVCR2.

Summary: Ethanolamine movement is the process directly performed by the transporter.

Reason: This GOC process inference is grounded in the existing ethanolamine-transporter activity GO:0034228. Human FLVCR2 directly mediates uptake in PMID:38778100, corroborated by kinase-assisted uptake in PMID:38302740. Retain the corresponding process as core; FLVCR2 performs movement, not ethanolamine synthesis or phospholipid-synthetic chemistry.

Summary: Substrate-specific transport assertions make the broad transmembrane process redundant.

Reason: Human FLVCR2 directly transports choline and ethanolamine across membranes. The retained substrate-specific transporter activities have GO:0055085 in their official part_of ancestry; choline and ethanolamine transport are separately retained. Mark this unspecific process as too general. This argument uses the verified cross-aspect part_of relation, not an incorrect claim that the substrate transport biological-process terms themselves descend from transmembrane transport.

Summary: Target-specific paralog comparison contradicts propagated heme export under tested conditions.

Reason: The heme-export IBD at PTN000858905 lies on the human FLVCR2 path, but target-specific functional evidence challenges its scope across the paralog split. The separately inspected original PMID:15369674 Results and Figure 3C compare human FLVCR1 with the chromosome-14q construct in rat NRK cells: radiolabeled heme decreases during washout for FLVCR1 but not the 14q construct. PMID:20823265 explicitly identifies hFLVCR14q as human FLVCR2 and reports the same prior non-export result in its Results and Discussion, providing independently accessible corroboration. The propagated export assertion therefore conflicts with the target-specific comparator under the tested conditions. This does not imply that uptake logically excludes export, that every possible heme-export condition was tested, or that choline release establishes heme release.

Summary: Mouse endothelial physiology and separate human evidence support core choline transport at the blood–brain barrier.

Reason: The Ensembl inference from experimentally studied mouse Flvcr2 Q91X85 is consistent with FLVCR2 directly performing choline movement at the blood–brain barrier. PMID:38693257 reports reduced brain tracer uptake after endothelial knockout in mice, human brain endothelial immunostaining and reduced choline uptake after endogenous FLVCR2 knockdown in human iHBECs. PMID:38302740 separately supports mouse endothelial choline uptake and clearance-related physiology alongside direct human-protein transport. Together these support the retained core BBB process, now explicit in the choline core. Luminal uptake and a possible abluminal-release step are compatible models, but the full route to parenchyma and the final clearance destination are not resolved by these studies. Human staining and cell uptake are not direct human in-vivo transendothelial flux measurements; the purified and HEK293-construct assays in PMID:38693257 use mouse protein.

Summary: Conserved endothelial choline movement supports the core blood–brain-barrier process.

Reason: Q91X85 is the experimentally studied mouse Flvcr2 ortholog. PMID:38302740 shows reduced brain uptake after high-dose intravenous choline and a separate clearance interpretation based on LPC-derived choline accumulation. PMID:38693257 independently finds reduced brain tracer uptake in adult endothelial-knockout mice; human brain endothelial staining and endogenous human iHBEC knockdown provide separate human localization and uptake support. FLVCR2 performs the substrate movement itself, so this supported physiological process belongs in the choline-transport core. Its complete luminal-to-parenchymal route is not established: the latter paper explicitly leaves abluminal export for further study, and the former does not resolve plasma release versus endothelial retention. No direct human in-vivo flux, obligatory proton coupling or natural short-product activity is inferred.