COLEC10

COLEC10 encodes collectin liver 1 (CL-L1), a pattern-recognition molecule of the innate immune system that also serves critical roles in embryonic morphogenesis and hepatocellular homeostasis. CL-L1 contains an N-terminal cysteine-rich domain, a collagen-like domain, a neck domain, and a C-type carbohydrate recognition domain (CRD) that binds mannose, fucose, N-acetylglucosamine, and galactose; it hetero-oligomerizes with CL-K1 (COLEC11) to form circulating CL-LK complexes that activate the lectin complement pathway via MASPs (PMID:10224141, PMID:27377710). Loss-of-function mutations in COLEC10 cause 3MC syndrome, a Mendelian craniofacial dysostosis, by impairing CL-L1 secretion and its chemoattractant activity for migrating cells during palate and craniofacial development (PMID:28301481, PMID:34740859). Intracellularly, COLEC10 directly binds the ER chaperone GRP78 through its CRD, sequestering GRP78 and thereby activating PERK- and IRE1α-dependent ER stress responses that suppress hepatocellular carcinoma cell growth; it also inhibits Wnt/β-catenin signaling by upregulating WIF1 and promoting β-catenin interaction with the CK1α destruction complex, with KLHL22 acting as an E3 ligase adaptor that monoubiquitinates and destabilizes COLEC10 (PMID:36925047, PMID:39080215).

1. 1999 High

   Identification of CL-L1 as a novel collectin family member resolved the gene's domain architecture and established its liver-enriched expression, but the weak mannose-binding observed with truncated fusion proteins left the physiological ligand specificity uncertain.

   Evidence cDNA cloning, Northern blot, E. coli fusion protein carbohydrate-binding assays

   PMID:10224141

   Open questions at the time

   • Full-length protein binding specificity not tested
   • Biological function unknown
   • Secretion vs. intracellular retention unclear
2. 2012 Medium

   Detailed CRD specificity profiling clarified that CL-L1 preferentially binds mannose, fucose, GlcNAc, and galactose, and revealed an apparent cytosolic restriction of CL-L1 distinct from the secreted CL-K1, raising questions about how the two collectins interact.

   Evidence Carbohydrate specificity analyses and biochemical fractionation of hepatocytes

   PMID:22475410

   Open questions at the time

   • Mechanism of intracellular retention not defined
   • Heteromeric complex formation with CL-K1 not yet demonstrated directly
3. 2016 Medium

   Demonstration that CL-L1 and CL-K1 form circulating CL-LK heteromeric complexes that activate the lectin complement pathway via MASPs established the functional unit for innate immune pattern recognition.

   Evidence Biochemical characterization and complement activation assays

   PMID:27377710

   Open questions at the time

   • Stoichiometry and structure of CL-LK complex unresolved
   • Relative contribution of CL-L1 vs. CL-K1 CRDs to ligand recognition unknown
4. 2017 High

   Linking COLEC10 loss-of-function mutations to 3MC syndrome and showing impaired CL-L1 secretion established a direct developmental role for the gene in craniofacial morphogenesis, independent of complement activation.

   Evidence Functional characterization of patient mutations (expression/secretion assays), in situ hybridization in murine embryonic palate, genetic linkage in 3MC families

   PMID:28301481

   Open questions at the time

   • Downstream signaling pathway driving neural crest migration not identified
   • Whether complement activation is required for the developmental phenotype unclear
5. 2018 Medium

   Immunohistochemical mapping across human tissues showed widespread CL-L1/CL-K1 co-expression in secretory epithelia, demonstrating that local peripheral synthesis—not solely hepatic production—generates CL-LK complexes.

   Evidence Monoclonal antibody immunohistochemistry and mRNA in situ on human tissue panels

   PMID:30108587

   Open questions at the time

   • Functional relevance of extrahepatic CL-LK production not tested
   • Whether tissue-specific CL-LK activates complement locally unknown
6. 2021 Medium

   A COLEC10 frameshift variant that preserves secretion but abolishes chemoattractant activity demonstrated that the CRD-containing C-terminus is required for CL-L1's role as a cell migration guidance cue, mechanistically separating secretion from biological function.

   Evidence Cell migration/chemotaxis assay with wild-type vs. mutant recombinant CL-L1, plasma level measurement

   PMID:34740859

   Open questions at the time

   • Receptor mediating chemoattractant response unidentified
   • Whether this variant causes 3MC in homozygous state not confirmed
7. 2023 High

   Discovery that intracellular COLEC10 directly binds GRP78 via its CRD to release ER stress transducers PERK and IRE1α revealed a cell-autonomous tumor-suppressive mechanism through UPR activation and ER structural disruption in HCC cells.

   Evidence Co-immunoprecipitation with domain-deletion constructs, Western blot for p-PERK/p-IRE1α/ATF4/DDIT3/XBP1s, electron microscopy, in vivo xenograft assays

   PMID:36925047

   Open questions at the time

   • Whether CRD-GRP78 interaction is carbohydrate-dependent or protein-protein unknown
   • Relevance of this mechanism outside HCC not tested
8. 2023 Medium

   Single-cell transcriptomics reassigned COLEC10's primary hepatic source to quiescent hepatic stellate cells rather than hepatocytes, and overexpression experiments linked COLEC10 to induction of fibrosis-associated ECM genes.

   Evidence scRNA-seq re-analysis, lentiviral overexpression in LX-2 stellate cells, RT-qPCR for COL1A1/COL1A2/COL3A1/MMP2

   PMID:38036508

   Open questions at the time

   • Stellate cell activation state dependency not established
   • Whether endogenous COLEC10 knockdown reduces fibrosis not tested
   • In vivo fibrosis model lacking
9. 2024 Medium

   Mechanistic dissection of COLEC10's tumor-suppressive role showed it inhibits Wnt/β-catenin signaling by upregulating WIF1 and promoting β-catenin association with the CK1α destruction complex, while KLHL22 was identified as the E3 ligase adaptor mediating COLEC10 monoubiquitination and turnover.

   Evidence Wnt/β-catenin reporter assay, Co-IP for β-catenin–CK1α, sphere formation and limiting dilution xenograft assays, Western blot for ubiquitination

   PMID:39080215

   Open questions at the time

   • Direct binding site on β-catenin/CK1α not mapped
   • Whether Wnt suppression and GRP78-mediated ER stress are independent or connected pathways unknown
   • KLHL22 ubiquitination site on COLEC10 not identified

• The receptor or co-receptor through which secreted CL-L1 exerts its chemoattractant function during embryonic development remains unidentified, and the relationship between the extracellular complement-activating role and the intracellular ER-stress/Wnt-suppressive mechanisms has not been integrated.
• No chemoattractant receptor identified
• No structural model of CL-LK heteromer
• Interplay between complement activation, ER stress induction, and Wnt pathway suppression unresolved