FLVCR2 notes

2026-10-29: accepted evidence synthesis, before canonical writing

These notes prepare an eventual review of human FLVCR2 (UniProt Q9UPI3; HGNC:20105) from the accepted private matrix. They do not record a canonical fetch, seed, source acquisition, validation, render, history scaffold or publication. The coordinating writer still needs release and fresh ownership checks, including actual-main reuse of the shared PMID:15369674 source. No worktree or source cache was changed for these drafts.

The accepted plan preserves all 30 original QuickGO contexts and proposes 16 ACCEPT, 10 KEEP_AS_NON_CORE, 3 TOO_GENERAL and 1 REMOVE. It contains two cores and two natural products, with no NEW annotations or publication quotations. The private exporter and seed-key replay each contain 30 distinct rows; the future genuine seed must be compared with this baseline before these counts are treated as canonical. Exact source objects, original identifiers and actions are retained in the adjacent private context ledger.

The best-supported core functions are choline and ethanolamine transmembrane transport by characterized full-length human FLVCR2. Human HEK293 uptake, separate choline release, transport-site mutants and human-protein yeast complementation support choline movement. CHKA/CHAT-dependent metabolic trapping affects measured accumulation; it does not make FLVCR2 a synthesis enzyme or turn the cellular experiment into purified-protein reconstitution. Human FLVCR2 choline-bound structural evidence supports substrate recognition separately from transport. PMID:38302740(https://pubmed.ncbi.nlm.nih.gov/38302740/), PMID:38778100(https://pubmed.ncbi.nlm.nih.gov/38778100/)

Ethanolamine uptake is condition dependent. PMID:38302740 reports kinase-assisted uptake after a negative unassisted condition, while PMID:38778100 independently measures FLVCR2-dependent uptake and finds no substantial enhancement by ETNK1. The ethanolamine-bound structure and specifically reported ethanolamine washout in the latter paper concern FLVCR1 and are not transferred to FLVCR2. The two proposed cores therefore pair GO:0015220 with GO:0015871 and GO:0034228 with GO:0034229, both at GO:0005886 plasma membrane. Separate kinases perform precursor phosphorylation.

The blood–brain barrier contexts retain their physiological transport interpretation with mouse in vivo limits. Endothelial knockout/tracer experiments include reduced brain uptake after a high intravenous choline dose and a separate clearance interpretation involving LPC-derived choline. Export into plasma versus accumulation in endothelium remains unresolved. Human protein transport supports the ortholog inference, but this is not a direct human in vivo flux measurement. PMID:38693257 contributes official abstract/figure-caption evidence only; full Methods/Results were not recovered. PMID:38302740(https://pubmed.ncbi.nlm.nih.gov/38302740/), PMID:38693257(https://pubmed.ncbi.nlm.nih.gov/38693257/)

Historical heme uptake and binding remain non-core. Human FLVCR2 expressed in CHO cells and Xenopus oocytes, together with endogenous human TE671 knockdown, provides contextual uptake evidence; these assays do not isolate purified transporter flux. Hemin-agarose binding from cell lysates and purified human N-terminal-domain binding are distinct experiments. New amine-transport findings alone do not refute these observations. PMID:20823265(https://pubmed.ncbi.nlm.nih.gov/20823265/), PMID:32973183(https://pubmed.ncbi.nlm.nih.gov/32973183/)

Only raw18, the heme-export IBA GO:0097037, is removed. The ancestral placement is genuinely on the human FLVCR2 path. The objection is target-specific: the original human FLVCR versus chromosome-14q comparison in rat NRK cells found radiolabeled-heme washout for FLVCR1 but not the 14q construct; PMID:20823265 explicitly identifies that construct as human FLVCR2. This challenges functional inheritance across the paralog split under the tested conditions. It is not an argument from donor count, new substrate discovery, or the assumption that import universally excludes export. PMID:15369674(https://pubmed.ncbi.nlm.nih.gov/15369674/), PMID:20823265(https://pubmed.ncbi.nlm.nih.gov/20823265/)

Endogenous human THP-1 imaging supports contextual mitochondrial and ER-contact pools. These are retained outside the plasma-membrane core. ER-marker overlap at a contact does not resolve membrane insertion, and inner versus outer mitochondrial membrane remains unknown. Human imaging and the purified human 1–84 fragment are distinguished from mouse tissues and murine tagged/deletion constructs. The two official natural products are Q9UPI3-1 (526 residues) and Q9UPI3-2 (321 residues); the latter replaces native residues 1–18 and lacks 19–223. Neither fragment nor deletion experiments assign transport, heme binding or a location to that natural short product. PMID:32973183(https://pubmed.ncbi.nlm.nih.gov/32973183/)

The exact FLVCR2 assays underlying PMID:40972734 and the older plasma-membrane assertion from PMID:14729055 remain UNVERIFIED at source level because access was limited to authentic metadata/abstracts. Independently established human functions support retaining the existing terms; no wrong-gene claim or borrowed assay detail is warranted. The source guide specifies this distinction and the single original occurs_in extension that must survive serialization.

2026-10-29: canonical review and source acquisition

The existing F worktree was reused from accepted main2251f5c29ecb4479005a4e21f55d1c6e81dc7080. All41 earlier scratch files and11 prior branches were preserved, with no new environment or worktree. Fresh complete current/former-path inventories for269 open PRs showed no owner of the12 alias roots or11 dependencies. Eight exact-main sources were hydrated before genuine fetch; only three qualified missing publications were acquired.

The genuine seed produced30 rows and two natural products. All imported fields and order are preserved; the sole allowed additive source restoration is original raw1/id447598895 occurs_in plasma membrane, at genuine stored row6. Final actions are16 ACCEPT,10 KEEP_AS_NON_CORE,3 TOO_GENERAL and1 REMOVE. Two cores summarize characterized full-length choline and ethanolamine transport. The source guide and evidence synthesis are cited in the review and give self-contained public context and source provenance.

Reference-only support follows the explicit campaign user instructions, which take precedence over conflicting local skill requests for quotations. No new quotes or NEW annotations are added. Default validators remain unchanged. Prior provider authentication/quota failures are recorded as a reason for manual primary research without retries, not represented as a generated report.

Targeted validation, independent canonical peer review and a scaffolded Codex history record will be recorded after completion.

2026-10-29: newly available PMID:38693257 full text

The genuine normal fetch recovered full text for PMID:38693257, superseding the earlier private-preparation abstract/caption-only limit recorded above. Selected Results, Methods and Discussion were read independently. Mouse endothelial knockout supports in-vivo brain uptake; endogenous human iHBEC knockdown and postmortem human brain staining are separate human observations. The HEK293 transfection, purified binding, liposome and structural work use mouse FLVCR2, not human inserts. Proton gradients enhance the mouse liposome assay, but the authors report robust no-gradient transport and leave facilitative uniport versus proton coupling unresolved. No obligate coupled transport or human in-vivo tracer measurement is inferred. The two barrier-transfer reasons and source assessment were updated only for this access/scope improvement; all30 actions, imported contexts, two cores and natural products remain unchanged. PMID:38693257(https://pubmed.ncbi.nlm.nih.gov/38693257/).

2026-10-29: completed validation and independent peer review

Gene schema, term and best-practice validation, strict GOA consistency, report-only status, history schema, private HTML rendering, full context/source conservation and both natural-product sequence reconstructions passed. Computed status is COMPLETE with zero curation warnings. The shared runtime emitted a package deprecation notice; this is not a curation advisory. The unchanged product replay was retained after the two source-access reason updates.

An independent read-only scientific peer read all 30 decisions, 18 references, the description, both cores, both products and the complete authored documentation. It independently replayed the original source fields/order, raw-to-seed bijection, sole structured extension, 11 source hashes and both official FASTA identities. Selected primary checks included the original export comparator, the organellar imaging scope and the newly available PMID:38693257 mouse-versus-human assay distinctions. No correction remained.

All eight inherited normal sources and both genuine gene-source downloads remain unchanged. The three new publications were acquired only after ownership qualification. The 41 earlier scratch files and 11 previous branches remain intact, and no new environment or worktree was created. The explicit Codex history record was scaffolded through the repository CLI and finalized with these actual outcomes. The local checks do not substitute for subsequent PR and integration testing.

2026-10-29: independent PR review follow-up

The completed exact-head review requested explicit BBB core coverage and a fuller comparison of the historical heme results with PMID:38778100. Both BBB annotations remain ACCEPT; GO:0150104 is now represented in the choline core, with human brain staining and iHBEC uptake distinguished from mouse in-vivo tracer and purified-protein experiments. The full directional route across endothelial faces remains unresolved without negating the measured uptake contexts.

Heme uptake and binding remain KEEP_AS_NON_CORE after explicit consideration of the later nonconfirmation statement and amine-pocket evidence. The newer assays establish primary amine substrates but do not directly exclude heme flux or the independently measured human N-terminal heme interaction. Positive cellular uptake and knockdown observations support retaining the bounded historical activity; direct full-length heme translocation and physiological importance remain open. The export-IBA removal remains supported by the separately inspected original PMID:15369674 Figure 3C/Results, with checkable corroboration in PMID:20823265. Its VERIFIED reference judgment is retained despite the normal cache being abstract-only.

The source guide and evidence synthesis record the revised scope and original article locator. Author-written spacing and process descriptions were clarified without changing original machine contexts, actions, products, source caches or this prior journal. No new annotation or publication quotation is introduced. A new append-only Codex history record and actual verification outcomes will accompany canonical implementation.

2026-10-29: follow-up verification

Gene schema/term/best-practice validation, strict GOA consistency, report-only status, new-history validation, private rendering and exact accepted-proposal/source conservation passed. Status remains COMPLETE with zero curation warnings. Both unchanged natural-product records and sequence-source bytes retain their earlier successful reconstruction; no new sequence analysis is claimed. Independent scientific review read the exact proposed changes and source boundaries, and deterministic replay confirms those exact changes in the canonical record. All 30 machine contexts/actions, the original extension, 11 normal sources, both products and the earlier history remain unchanged. The prior journal prefix, 41 scratch files and 11 previous branch pins are preserved.