FLVCR2 source evidence

This evidence synthesis accompanies the review of all 30 genuine source contexts. It summarizes selected primary readings with the stated access, species and construct limits. The source guide records original contexts, cache hashes and the restored extension. No publication quotations or NEW annotations are introduced.

Transport and substrate recognition

PMID:38302740 — selected original Results/Methods available. Human FLVCR2 was tested in HEK293 cells with empty-vector, CHT1 and S203Y comparisons, and human-protein complementation was tested in yeast lacking Hnm1. Dose/time dependence, sodium replacement and release from preloaded cells support facilitative choline transport. CHKA/CHAT co-expression increases metabolic trapping. Kinase-assisted ethanolamine uptake must be considered alongside the earlier negative unassisted condition. Surface-localization controls separate the S203Y uptake defect from simple loss of abundance or surface targeting. Mouse endothelial knockout, tracer and metabolite experiments are separate from these human-protein assays. The uptake experiment supports brain influx under its tested condition; a separate clearance interpretation leaves the final plasma-versus-endothelial destination unresolved. These measured contexts support a BBB role without establishing a universal direction at every endothelial membrane face. Relevant existing rows: raw1/13/21 directly, with corroboration for other transport/orthology rows. Original reference

PMID:38778100 — selected original Results/Methods available. Human FLVCR2 choline-bound structures, ligand-dependent fluorescence and transport-site mutations support substrate recognition. HEK293 radiotracer uptake, dose/time curves and separate choline washout support cellular movement; membrane-targeted GFP colocalization supports plasma-membrane localization. FLVCR2 ethanolamine uptake is positive, but ETNK1 does not substantially enhance it in this study. The ethanolamine-bound structure and specifically reported ethanolamine washout concern FLVCR1. No human FLVCR2 proteoliposome flux experiment is claimed from these cellular data. Relevant direct rows: raw2/11/14/22; corroboration supports raw10 and the electronic activity/process assignments. Original reference

PMID:38693257 — selected original Results/Methods now available through the genuine normal fetch. Adult endothelial-knockout mice show reduced brain radiotracer uptake; human brain immunostaining and human iHBEC siRNA-associated uptake reduction are separate observations. Methods identify mouse FLVCR2 in the HEK293 overexpression, purified binding, proteoliposome and structural experiments. Protein-free liposomes control background uptake; inward proton gradients enhance transport, whereas sodium gradients do not in the tested mouse system. The authors leave proton coupling versus facilitative uniport unresolved; pH enhancement alone is not a coupling mechanism assignment. They report robust transport without a proton gradient. These data strengthen the existing barrier-role interpretation without transferring purified mouse kinetics or coupling to human FLVCR2. No figure pixels, supplement-table values or source data were independently reanalysed. Relevant corroborated rows remain raw10/19/20. Original reference

PMID:40972734 — authentic metadata/abstract only. Exact FLVCR2 experimental support remains UNVERIFIED. Raw3 and raw15 retain independently established choline activity/process terms using PMID:38302740 and PMID:38778100, while preserving the original citation. No kinetics or assay parameters of another SLC are assigned to FLVCR2, and limited abstract coverage is not treated as misattribution. Original reference

Heme evidence and the export IBA

PMID:20823265 — original Methods/Results read in the accepted consultation. Human FLVCR2 expression increases ZnMP uptake in hamster CHO cells and radiolabeled-hemin accumulation in Xenopus oocytes; two siRNAs reduce analog uptake in human TE671 cells. HA-tagged human protein from CHO lysates binds hemin-agarose with soluble-hemin competition and a feline thiamine-transporter comparison. Uptake, perturbation and binding provide different kinds of evidence. These are not an isolated full-length-protein affinity or reconstituted-flux measurement. Raw4/5 heme activity and raw6/7 binding remain non-core. The paper also explicitly identifies the chromosome-14q construct in PMID:15369674 as human FLVCR2. Original reference

PMID:15369674 — retained original publisher PDF and selected comparative result/caption read. In rat NRK cells expressing the human constructs, radiolabeled-heme washout distinguished FLVCR1 from the chromosome-14q paralog. Together with the explicit identity link in PMID:20823265, the negative result for the latter supports removing the propagated FLVCR2 export assertion raw18. The review challenges the functional scope of the ancestral placement, not its mechanical descent or donor count. It does not claim that every export condition was tested, that import logically prevents export, or that choline release establishes heme release. The normal source is shared with FLVCR1 and was reused byte-for-byte from its accepted actual main merge after fresh ownership qualification. Original reference

Organellar pools and product boundaries

PMID:32973183 — original main body plus selected supplementary Figure 10/caption available. Purified human FLVCR2 residues 1–84 bind heme by co-elution and optical titration, with histidine substitutions affecting the response. This supports raw8 without transferring murine full-length cellular experiments to the human fragment. Endogenous human THP-1 imaging, including knockout staining controls, supports a mitochondrial pool; selected supplementary imaging also supports a fraction at ER–mitochondrial contacts. Mouse-brain fractionation and murine tagged-protein studies are separate corroboration. Retain raw24/25 ER-membrane and raw28/29 mitochondrial-membrane contexts as non-core, with unresolved ER-bilayer insertion and inner-versus-outer mitochondrial assignment. Figure 6 alternatives are models, not localization measurements. The engineered deletion and human fragment are not natural product Q9UPI3-2. Only the selected supplementary figure/caption was inspected; no source-data analysis is claimed. Original reference

PMID:14729055 — verified identity and abstract only. Exact source-specific localization evidence for raw27 remains UNVERIFIED. Independent human surface localization in PMID:38302740 and PMID:38778100 supports ACCEPT at the existing term level. No calcium-chelate transport mechanism, pituitary assay detail or natural-product localization is inferred from the old abstract. Original reference

Electronic evidence and ontology scope

The accepted replay places all four incoming IBAs on the exact human Q9UPI3 path in PTHR10924: raw4/6/18 originate at PTN000858905; raw23 originates at PTN000858822. The 526-residue target matches the retained MSA, and all eight rows in the normal PAINT slice match the original GAF. Preserve that slice. Target-derived experimental seeds are valid grounding, not circularity. Heme activity/binding remain non-core; only export is removed on the comparative target-specific evidence above.

Raw9 GO:0022857 is too general relative to the retained substrate-specific molecular functions. Raw17 GO:0055085 is too general using the verified molecular-function part_of ancestry, not an invented biological-process is_a edge. Raw23 GO:0016020 is too general relative to the retained plasma-membrane location. Mouse Q91X85 donor identity and experimental annotations support the relevant orthology rows without becoming additional human experiments.

The two cores remain amine transport, with the associated transport processes and plasma-membrane location; the choline core also explicitly includes the already accepted blood–brain-barrier process. Heme uptake/binding, organellar pools and choline binding are retained contextual assertions. There is no proposed synthesis-enzyme activity, receptor/sensor function, new process annotation or functional assignment to the 321-residue product.

Reproducible identity and phylogenetic provenance

The original data are available through the linked official endpoints; hashes identify the exact inspected versions. The tree and MSA contain 359 records. Q9UPI3 target PTN002475066 matches 526 ungapped residues, SHA256 ab26eb4772405a41571e4e954cd6914ecbbabc07446d3c5fba1f23f288706cd4. This identity result does not independently establish any substrate.

Target path: PTN000858822 → PTN000100592 → PTN000100594 → PTN000858823 → PTN002475064 → PTN000858905 → PTN000100648 → PTN000100649 → PTN000100650 → PTN008313312 → PTN000100651 → PTN002589196 → PTN008508740 → PTN000100679 → PTN000100680 → PTN000100681 → PTN000100682 → PTN000100683 → PTN000100684 → PTN002589197 → PTN000100685 → PTN002475066. The heme origins at PTN000858905 have Eumetazoa taxonomy; the membrane origin PTN000858822 is Eukaryota. Four incoming origins and all eight existing normal PAINT records match the original IBD GAF. API and PAINT releases are distinct snapshots; exact joins, not assumed release identity, support the replay.

These identity checks do not assign full-length activities to the short product. No new phylogenetic function, residue mechanism or natural-product activity is inferred.

Review follow-up: mechanistic counterevidence and core participation

PMID:38778100 Discussion explicitly describes the earlier heme-uptake interpretation as unconfirmed and presents choline/ethanolamine as primary substrates. Its human FLVCR2 structure and W102-centred cation–π recognition support small-amine coordination, and Q191A abolishes the measured choline and ethanolamine uptake. Those assays do not test heme flux, and the authors also acknowledge SLC substrate promiscuity. This is a substantive reason to keep heme outside the amine core, not an observed negative heme-transport experiment.

PMID:20823265 instead reports positive accumulation in human-FLVCR2-expressing CHO cells and oocytes, together with two-siRNA effects in human TE671 cells. These complementary experiments justify KEEP_AS_NON_CORE rather than MARK_AS_OVER_ANNOTATED while direct full-length translocation and physiological importance remain unresolved. Its lysate hemin-agarose assay and the independently purified human residues 1–84 binding in PMID:32973183 support a separate binding capacity. A transmembrane amine pocket does not invalidate that N-terminal interaction; binding alone does not prove transport.

For GO:0150104, FLVCR2 performs the substrate movement rather than serving merely as a necessary downstream factor. PMID:38693257 human brain endothelial staining and endogenous iHBEC uptake support the human scope, separately from mouse in-vivo endothelial-knockout tracer uptake and mouse-protein reconstitution. Both BBB annotations remain ACCEPT and the process is included in the choline core. Discussion in that paper explicitly leaves abluminal export to brain parenchyma for further study; compatible luminal-uptake/abluminal-release models are not a measured complete transport route. No obligatory proton-coupled mechanism is assigned.

The sole heme-export removal remains anchored to the inspected original PMID:15369674 Results and Figure 3C (article PDF), with the explicit identity link and non-export corroboration in the full cached PMID:20823265 Results/Discussion. The original PDF was retrieved on 2026-10-28T20:37:20.050905+00:00, 269318 bytes, SHA256 b386aa73c0cdd4cc0b8b56185729c2c80e1aa05d353f67a572561585d08f8be6. The normal abstract-only cache is preserved; its limited content does not erase the separate primary inspection.