Component

Human LMBD1 lysosomal membrane protein

Human LMBD1 lysosomal membrane protein

5 recorded relationships. Experimental role, claim status and evidence remain attached to each record.

Read recorded mechanisms Open recursive mind map

How nutrients influence it

Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.

How nutrients reach it in more than one step

Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.

Tracing routes…

What it does

Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.

Recorded relationships

What it acts on

  1. LMBD1-only proteoliposomes had no detectable cobalamin transport in the same reconstitution system in which ABCD4 transported cobalamin.

    Human LMBD1 lysosomal membrane protein → Vitamin B12 (cobalamins) source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Results: Figures 3, 4, 5; Experimental procedures: liposomes and transport assays
    experimental_model
    Purified human ABCD4/LMBD1 in synthetic liposomes after yeast expression
    exposure
    LMBD1-only versus ABCD4-containing proteoliposomes
    limitations
    Assay-specific absence of activity does not negate LMBD1’s cellular targeting role.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    The escort alone did not transport B12 in this membrane assay.
    primary_references
    [kitai-2021-abcd4-transport] The lysosomal protein ABCD4 can transport vitamin B12 across liposomal membranes in vitro (2021). https://pubmed.ncbi.nlm.nih.gov/33845046/ DOI: 10.1016/j.jbc.2021.100654
    tissue_or_cell_type
    Cell-free membrane system

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 627–639

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human ABCD4/LMBD1 in synthetic liposomes after yeast expression · source_derived_draft · unverified_draft

    ### b12-lmbd1-no-direct-transport LMBD1-only proteoliposomes had no detectable cobalamin transport in the same reconstitution system in which ABCD4 transported cobalamin. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: The escort alone did not transport B12 in this membrane assay. organism: Homo sapiens tissue_or_cell_type: Cell-free membrane system experimental_model: Purified human ABCD4/LMBD1 in synthetic liposomes after yeast expression limitations: Assay-specific absence of activity does not negate LMBD1’s cellular targeting role. exposure: LMBD1-only versus ABCD4-containing proteoliposomes cross_nutrient: false evidence_location: Results: Figures 3, 4, 5; Experimental procedures: liposomes and transport assays [kitai-2021-abcd4-transport] The lysosomal protein ABCD4 can transport vitamin B12 across liposomal membranes in vitro (2021). https://pubmed.ncbi.nlm.nih.gov/33845046/ DOI: 10.1016/j.jbc.2021.100654
    Complete structured claim and evidence

  2. In HuH7 cells expressing human ABCD4-HA, adding LMBD1-GFP shifted ABCD4 from an ER-like distribution toward LAMP1-positive lysosomes.

    Human LMBD1 lysosomal membrane protein → Human ABCD4 lysosomal cobalamin transporter source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Results: Figures 1, 6, 7; Methods: cell lines and CRISPR
    experimental_model
    Human HuH7 tagged-protein localization
    exposure
    ABCD4-HA stable expression and transient LMBD1-GFP
    limitations
    Tagged overexpression; colocalization does not measure cobalamin flux.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    LMBD1 helped the B12 transporter reach lysosomes.
    primary_references
    [kawaguchi-2016-lmbd1-escort] Translocation of the ABC transporter ABCD4 from the endoplasmic reticulum to lysosomes requires the escort protein LMBD1 (2016). https://pubmed.ncbi.nlm.nih.gov/27456980/ DOI: 10.1038/srep30183
    tissue_or_cell_type
    Hepatoma cell line

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 571–583

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human HuH7 tagged-protein localization · source_derived_draft · unverified_draft

    ### b12-lmbrd1-escort-huh7 In HuH7 cells expressing human ABCD4-HA, adding LMBD1-GFP shifted ABCD4 from an ER-like distribution toward LAMP1-positive lysosomes. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: LMBD1 helped the B12 transporter reach lysosomes. organism: Homo sapiens tissue_or_cell_type: Hepatoma cell line experimental_model: Human HuH7 tagged-protein localization limitations: Tagged overexpression; colocalization does not measure cobalamin flux. exposure: ABCD4-HA stable expression and transient LMBD1-GFP cross_nutrient: false evidence_location: Results: Figures 1, 6, 7; Methods: cell lines and CRISPR [kawaguchi-2016-lmbd1-escort] Translocation of the ABC transporter ABCD4 from the endoplasmic reticulum to lysosomes requires the escort protein LMBD1 (2016). https://pubmed.ncbi.nlm.nih.gov/27456980/ DOI: 10.1038/srep30183
    Complete structured claim and evidence

  3. Transfection with wild-type LMBD1 restored cobalamin coenzyme synthesis and function in cultured fibroblasts from individuals with the cblF defect.

    Human LMBD1 lysosomal membrane protein → Cellular cobalamin coenzyme synthesis source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    cross_nutrient
    false
    evidence_location
    Abstract; Figure 4 caption
    experimental_model
    Human cblF patient fibroblast complementation
    exposure
    Wild-type LMBD1 expression construct
    limitations
    Cultured-cell experiment; not dietary deficiency, a serum B12 threshold, or a human treatment effect.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Restoring the missing lysosomal protein let patient cells make usable B12 cofactors.
    primary_references
    [rutsch-2009-lmbrd1] Identification of a putative lysosomal cobalamin exporter altered in the cblF defect of vitamin B12 metabolism (2009). https://pubmed.ncbi.nlm.nih.gov/19136951/ DOI: 10.1038/ng.294
    tissue_or_cell_type
    Skin-derived fibroblasts
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 543–555

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human cblF patient fibroblast complementation · source_derived_draft · unverified_draft

    ### b12-lmbrd1-rescue Transfection with wild-type LMBD1 restored cobalamin coenzyme synthesis and function in cultured fibroblasts from individuals with the cblF defect. Condition category: machinery_impairment nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Restoring the missing lysosomal protein let patient cells make usable B12 cofactors. organism: Homo sapiens tissue_or_cell_type: Skin-derived fibroblasts experimental_model: Human cblF patient fibroblast complementation limitations: Cultured-cell experiment; not dietary deficiency, a serum B12 threshold, or a human treatment effect. exposure: Wild-type LMBD1 expression construct cross_nutrient: false evidence_location: Abstract; Figure 4 caption [rutsch-2009-lmbrd1] Identification of a putative lysosomal cobalamin exporter altered in the cblF defect of vitamin B12 metabolism (2009). https://pubmed.ncbi.nlm.nih.gov/19136951/ DOI: 10.1038/ng.294
    Complete structured claim and evidence

What acts on it

  1. Human ABCD4 Y482A showed markedly impaired association with LMBD1 in HEK293T co-immunoprecipitation compared with wild-type ABCD4.

    Human ABCD4 Y482A → Human LMBD1 lysosomal membrane protein source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    cross_nutrient
    false
    evidence_location
    Figure 4c
    experimental_model
    HEK293T human tagged-protein interface mutagenesis
    exposure
    ABCD4-HA Y482A plus LMBD1-GFP-Flag versus wild type
    limitations
    Experimental Y482A substitution and overexpression; no claim that this is a disease allele or a direct flux measurement.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Changing the transporter’s interface weakened its association with the escort.
    primary_references
    [liu-2026-abcd4-interface] Structural basis for LMBD1-dependent trafficking and cobalamin export of ABCD4 (2026). https://pubmed.ncbi.nlm.nih.gov/42303638/ DOI: 10.1038/s41467-026-74552-5
    tissue_or_cell_type
    Human embryonic kidney-derived cell line
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 949–961

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · HEK293T human tagged-protein interface mutagenesis · source_derived_draft · unverified_draft

    ### b12-abcd4-y482a-binding Human ABCD4 Y482A showed markedly impaired association with LMBD1 in HEK293T co-immunoprecipitation compared with wild-type ABCD4. Condition category: machinery_impairment nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Changing the transporter’s interface weakened its association with the escort. organism: Homo sapiens tissue_or_cell_type: Human embryonic kidney-derived cell line experimental_model: HEK293T human tagged-protein interface mutagenesis limitations: Experimental Y482A substitution and overexpression; no claim that this is a disease allele or a direct flux measurement. exposure: ABCD4-HA Y482A plus LMBD1-GFP-Flag versus wild type cross_nutrient: false evidence_location: Figure 4c [liu-2026-abcd4-interface] Structural basis for LMBD1-dependent trafficking and cobalamin export of ABCD4 (2026). https://pubmed.ncbi.nlm.nih.gov/42303638/ DOI: 10.1038/s41467-026-74552-5
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. In transfected HEK293 cells, LMBD1 carrying 233YERL-to-AAAA mislocalized partly to the cell surface; coexpressed ABCD4 followed its distribution instead of normal lysosomal targeting.

    Human LMBD1 233YERL-to-AAAA → Human ABCD4 lysosomal cobalamin transporter source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    cross_nutrient
    false
    evidence_location
    Results: Figures 1, 6, 7; Methods: cell lines and CRISPR
    experimental_model
    HEK293 experimental sorting-motif mutagenesis
    exposure
    Human LMBD1-GFP 233YERL/AAAA plus ABCD4-HA
    limitations
    Experimental four-residue substitution; microscopy does not establish direct vitamin transport.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Changing the escort’s sorting sequence sent the transporter to the wrong location.
    primary_references
    [kawaguchi-2016-lmbd1-escort] Translocation of the ABC transporter ABCD4 from the endoplasmic reticulum to lysosomes requires the escort protein LMBD1 (2016). https://pubmed.ncbi.nlm.nih.gov/27456980/ DOI: 10.1038/srep30183
    tissue_or_cell_type
    Embryonic kidney-derived cell line
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 599–611

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · HEK293 experimental sorting-motif mutagenesis · source_derived_draft · unverified_draft

    ### b12-lmbd1-sorting-mutant In transfected HEK293 cells, LMBD1 carrying 233YERL-to-AAAA mislocalized partly to the cell surface; coexpressed ABCD4 followed its distribution instead of normal lysosomal targeting. Condition category: machinery_impairment nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Changing the escort’s sorting sequence sent the transporter to the wrong location. organism: Homo sapiens tissue_or_cell_type: Embryonic kidney-derived cell line experimental_model: HEK293 experimental sorting-motif mutagenesis limitations: Experimental four-residue substitution; microscopy does not establish direct vitamin transport. exposure: Human LMBD1-GFP 233YERL/AAAA plus ABCD4-HA cross_nutrient: false evidence_location: Results: Figures 1, 6, 7; Methods: cell lines and CRISPR [kawaguchi-2016-lmbd1-escort] Translocation of the ABC transporter ABCD4 from the endoplasmic reticulum to lysosomes requires the escort protein LMBD1 (2016). https://pubmed.ncbi.nlm.nih.gov/27456980/ DOI: 10.1038/srep30183
    Complete structured claim and evidence

In the sources

Preserved passages that mention this component, quoted exactly. Open one to read it in context.

    This is a research prototype built from draft material. It is not medical advice, and its statements still await verification against the original studies.

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