{"id":"4008e747-845e-52fb-93f5-a94706256380","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-abs-cd320-cellular-delivery","predicate":"mediates","statement":"The human receptor identified as CD320 binds transcobalamin-cobalamin at the plasma membrane and internalizes the carrier-vitamin complex by endocytosis.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"5b28029b-fd41-5296-8fde-1d5396feda4d","mechanism_event_label":"CD320 brings carrier-bound B12 into cells.","subject":{"id":"99cb2dd2-433b-5c71-b1bc-5be3fbeaf213","slug":"cd320","display_name":"Human transcobalamin receptor / CD320","entity_type_key":"protein"},"object":{"id":"e78d53a1-0ffb-5dc3-8891-83df0f32f6fa","slug":"holo-tc-cellular-uptake","display_name":"Cellular uptake of transcobalamin-bound cobalamin","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"5b28029b-fd41-5296-8fde-1d5396feda4d","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-abs-cd320-cellular-delivery-event","event_type":"biochemical_relationship","label":"CD320 brings carrier-bound B12 into cells.","description":"The human receptor identified as CD320 binds transcobalamin-cobalamin at the plasma membrane and internalizes the carrier-vitamin complex by endocytosis.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"b6d9b937-895d-5e0a-8cc5-0454a0b7d373","slug":"vitamin-b12","display_name":"Vitamin B12 (cobalamins)","entity_type_key":"chemical_species"},"role":"nutrient","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"81bccdbc-ffba-51bb-aa61-bce4b43e4103","slug":"tcn2","display_name":"Human transcobalamin / TCN2","entity_type_key":"protein"},"role":"carrier","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"c0d594d4-1445-57e7-b689-d2fbbb2dc00a","slug":"human-holotranscobalamin","display_name":"Human transcobalamin-cobalamin complex","entity_type_key":"protein_complex"},"role":"cargo","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"99cb2dd2-433b-5c71-b1bc-5be3fbeaf213","slug":"cd320","display_name":"Human transcobalamin receptor / CD320","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"e78d53a1-0ffb-5dc3-8891-83df0f32f6fa","slug":"holo-tc-cellular-uptake","display_name":"Cellular uptake of transcobalamin-bound cobalamin","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"false","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human receptor identification and functional characterization","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"TC-cobalamin complex presented to receptor","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"No universal uptake rate, tissue sufficiency threshold, or assertion that this is the sole B12 entry route.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-b12","display_name":"Vitamin B12 (cobalamins)","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"CD320 brings carrier-bound B12 into cells.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[quadros-2009-cd320] The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin. (2009). https://pubmed.ncbi.nlm.nih.gov/18779389/ DOI: 10.1182/blood-2008-05-158949","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Plasma-membrane endocytosis","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"2bf70a3c-c7f4-5d3f-bb8a-6c7bd289df61","evidence_kind":"source_excerpt","locator":"Lines 374-385","start_line":374,"end_line":385,"excerpt":"### b12-abs-cd320-cellular-delivery\nThe human receptor identified as CD320 binds transcobalamin-cobalamin at the plasma membrane and internalizes the carrier-vitamin complex by endocytosis.\nCondition category: normal\nnutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: CD320 brings carrier-bound B12 into cells.\norganism: Homo sapiens\ntissue_or_cell_type: Plasma-membrane endocytosis\nexperimental_model: Human receptor identification and functional characterization\nlimitations: No universal uptake rate, tissue sufficiency threshold, or assertion that this is the sole B12 entry route.\nexposure: TC-cobalamin complex presented to receptor\ncross_nutrient: false\n[quadros-2009-cd320] The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin. (2009). https://pubmed.ncbi.nlm.nih.gov/18779389/ DOI: 10.1182/blood-2008-05-158949","model_system":"Human receptor identification and functional characterization","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [quadros-2009-cd320] The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin. (2009). https://pubmed.ncbi.nlm.nih.gov/18779389/ DOI: 10.1182/blood-2008-05-158949","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"73145023-2982-5848-aff2-8d8875d6b9c5","stable_key":"import-7fc92b9e-9cbf-556e-8719-6b5244625250","title":"Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text.","file_path":"","sha256":"ad5b3a51d36e856aa7fdfd1cc23f690b094689bad87d28e1a621a54675a01c92","revision_id":"118bd616-0c13-549f-bfeb-bc439715b89c","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}