| Concept/Entity | Current understanding | Evidence type | Key quantitative/statistical data if available | Primary recent source(s) with year |
|---|---|---|---|---|
| Protein type / topology | Human LMAN1 (ERGIC-53; UniProt P49257) is a type I transmembrane L-type lectin cargo receptor of the early secretory pathway. It has an N-terminal luminal carbohydrate-recognition domain (CRD), a long luminal stalk, a single-pass TM helix, and a short cytosolic tail carrying trafficking motifs including KKFF for ER/Golgi cycling. (pqac-00000001, pqac-00000011) | Cryo-EM, structural analysis, review | Cytosolic tail is described as 12 residues in the 2023 review; full-length structure is ~340 Å long in cryo-EM figures. (pqac-00000011, pqac-00000028) | Watanabe et al., 2024; Tang & Ginsburg, 2023 |
| Lectin domain / glycan recognition | The luminal CRD binds mannose/high-mannose glycans in a Ca2+-dependent manner and contributes to selective recruitment of glycoprotein cargo. Some cargos appear glycan-dependent, whereas others can be recognized through lectin-independent protein interactions. (pqac-00000001, pqac-00000011, pqac-00000020) | Cryo-EM, prior structural/biochemical evidence summarized in review, rescue assays | No single universal cargo motif has been defined; carbohydrate-binding mutants can still rescue much of FVIII secretion in KO cells, supporting partial lectin-independent recognition. (pqac-00000020) | Watanabe et al., 2024; Tang & Ginsburg, 2023; Zhang et al., 2023 |
| Oligomerization | A major 2024 advance is that full-length ERGIC-53 was resolved as a homotetramer with a four-leaf-clover head and long flexible coiled-coil stalk, revising older hexamer models. Oligomerization is functionally linked to early secretory pathway trafficking. (pqac-00000001, pqac-00000009) | Cryo-EM, review | Cryo-EM consensus map at 3.51 Å; head substates at ~3.3–3.4 Å. (pqac-00000010) | Watanabe et al., 2024 |
| Binding partner MCFD2 | MCFD2 is a soluble EF-hand protein that forms a Ca2+-dependent 1:1 complex with LMAN1 and is required for efficient export of canonical cargos such as FV and FVIII. Recent structural work also indicates an N-terminal Zn2+-binding site in MCFD2 that may regulate cargo binding/release. (pqac-00000000, pqac-00000001, pqac-00000009, pqac-00000011) | Cryo-EM, structural analysis, review | F5F8D genetics are attributed to LMAN1 in ~70% of cases and MCFD2 in ~30% of cases. (pqac-00000011, pqac-00000027) | Watanabe et al., 2024; Tang & Ginsburg, 2023; Zhang et al., 2023 |
| Localization / trafficking cycle | LMAN1 cycles between the ER, ER-Golgi intermediate compartment (ERGIC), and Golgi/cis-Golgi, acting as a cargo receptor that helps recruit selected clients into COPII-mediated ER export and then recycles back through retrieval signals. (pqac-00000001, pqac-00000004, pqac-00000005) | Cryo-EM-informed structural analysis, review | Not quantified directly in the extracted evidence; pathway placement is consistent across review and structural sources. (pqac-00000001, pqac-00000005) | Watanabe et al., 2024; Tang & Ginsburg, 2023 |
| Canonical cargos: factor V and factor VIII | The best-established physiological role of the LMAN1-MCFD2 complex is ER-to-Golgi transport of coagulation factors V and VIII. Recent mechanistic work suggests MCFD2 is likely the primary interacting partner for FV/FVIII cargo, while LMAN1 mainly serves as the shuttling membrane carrier. (pqac-00000000, pqac-00000020) | Knockout/complementation, secretion assays, review | In human F5F8D, FV and FVIII are typically reduced to ~5%–30% of normal; some summaries cite average levels around 9%–15%. (pqac-00000025, pqac-00000021, pqac-00000027) | Zhang et al., 2023; Ma et al., 2024 |
| Additional cargos | Beyond FV/FVIII, evidence supports LMAN1-dependent trafficking of α1-antitrypsin (A1AT), Mac-2BP, MMP-9, and now thrombopoietin (TPO). A1AT appears to require both LMAN1 and MCFD2, whereas TPO is the first reported LMAN1-dependent cargo that is MCFD2-independent. (pqac-00000015, pqac-00000016, pqac-00000017, pqac-00000018, pqac-00000019) | Knockout mice, hepatocyte-specific deletion, co-IP, secretion assays, review | In Lman1-deficient mice, plasma TPO fell from about 230 × 10^3 to 120 × 10^3 pg/mL; hepatocyte-specific loss caused significant thrombocytopenia. (pqac-00000026) | Everett et al., 2024; Zhang et al., 2023; Watanabe et al., 2024 |
| Disease association: F5F8D | Biallelic loss-of-function variants in LMAN1 cause combined deficiency of coagulation factors V and VIII (F5F8D), a rare autosomal recessive bleeding disorder due to impaired cargo export rather than defects in F5 or F8 genes themselves. (pqac-00000011, pqac-00000023, pqac-00000027) | Human genetics, clinical case series, review | Prevalence is about 1:1,000,000 overall, but can be much higher in some consanguineous populations; a 2024 Russian series of 6 patients reported mean FV 5.7%, FVIII 9.0%, aPTT 85 s, and mean ISTH-BAT 23.5. (pqac-00000023, pqac-00000027) | Yakovleva et al., 2024; Tang & Ginsburg, 2023; Zhang et al., 2023 |
| Emerging therapeutic targeting | Experimental liver-directed GalNAc-siRNA knockdown of LMAN1 or MCFD2 reduces FVIII and prolongs coagulation times in mice, suggesting partial inhibition of the complex could be explored as an anticoagulation strategy. (pqac-00000021, pqac-00000024, pqac-00000025) | Preclinical RNAi, RT-qPCR, western blot, coagulation assays | After a single 3 mg/kg dose, hepatic LMAN1 mRNA fell to 19.97% ± 3.78% and MCFD2 mRNA to 32.22% ± 13.14%; liver LMAN1 and MCFD2 proteins fell to ~30% and ~50% of control, respectively. APTT peaked around day 13, and tail bleeding was generally not significantly increased. (pqac-00000024, pqac-00000025) | Ma et al., 2024 |
| Open mechanistic questions | Expert reviews emphasize that the full cargo repertoire remains limited and incompletely defined, the recognition motifs for many cargos are still unclear, and secretion may involve backup receptors or bulk-flow pathways. Recent structure work clarifies architecture but not all determinants of cargo specificity or in vivo release dynamics. (pqac-00000009, pqac-00000011, pqac-00000013) | Review, cryo-EM primary study | No definitive quantitative estimate of total cargo repertoire is available in the extracted evidence. (pqac-00000011, pqac-00000013) | Tang & Ginsburg, 2023; Watanabe et al., 2024 |


*Table: This table compiles compact, evidence-backed functional annotation points for human LMAN1/ERGIC-53, emphasizing mechanism, trafficking, cargo specificity, disease relevance, and recent 2023–2024 advances. It is useful as a quick reference for integrating structural, cell-biological, and clinical findings.*