CLDN16

Summary: Claudin-16 contributes the membrane structure of a paracellular channel.

Reason: The claudin-domain mapping agrees with CLDN16 incorporation into CLDN19-containing junctional strands and with heteromeric channel formation. CLDN16 does not form autonomous strands in the tested fibroblast and claudin-deficient epithelial models; its structural contribution is made within the junctional complex.

Summary: Specify the demonstrated interaction with ZO-1 PDZ domains.

Reason: The human CLDN16 terminal peptide binds in-vitro-translated ZO-1 PDZ domains, with wild-type versus T233R peptide and competition controls. Human HA-CLDN16 also coimmunoprecipitates endogenous canine ZO-1 in MDCK cells, consistent with the original O97758 partner. This supports PDZ domain binding without assigning ZO-1 scaffold activity to CLDN16.

Proposed replacements: PDZ domain binding

Summary: Refine the positive CLDN19 pair to experimentally supported heterodimerization.

Reason: The original human CLDN16–CLDN19 membrane two-hybrid and coimmunoprecipitation evidence is positive. Independent PMID:26446843 then resolves a heterodimer: human CLDN16 AF152101 and CLDN19 BC030524 coexpressed in HEK293 or Sf9 cells shift together in sucrose gradients, and crosslinking yields an approximately 41-kDa species detected by both antibodies, unlike the singly expressed monomers. GO:0046982 captures this demonstrated binding mode. The conclusion is limited to the expressed constructs and detergent-solubilized complexes; it does not establish every native tight-junction pore stoichiometry or all modern CLDN19 isoforms.

Proposed replacements: protein heterodimerization activity

Summary: Retain the curated CLDN19 product association.

Reason: The cited study reports selective CLDN16–CLDN19 association and mutual dependence of junctional localization, with mouse knockdown physiology and a membrane two-hybrid panel. The exact Q8N6F1-2 supporting product is preserved; the inspected text does not provide a new sequence alignment proving every assay construct matches that current product. The independent human heterodimer evidence in PMID:26446843 refines the gene-level pair in the earlier source row; this exact source/product assertion is retained without treating colocalization, FRET, or an unaligned isoform identifier as a separate stoichiometry measurement.

Summary: Retain the experimentally supported interaction with mouse claudin-14.

Reason: The paper explicitly uses mouse CLDN14 AF314089 and human CLDN16 AF152101. Membrane two-hybrid and reciprocal HEK293 coimmunoprecipitation assays support the pair, with noninteracting claudin and antibody controls; three exact positive MINT records match the original partner and PMID. The later strand-switching model does not erase these assay-specific observations.

Summary: Retain the CLDN16–CLDN19 association at the tested construct scope.

Reason: Human CLDN16 and CLDN19 constructs produce cis FRET in HEK293 cells and cooperate in enrichment at cell contacts. The Methods specify the short CLDN16 sequence from NM_006580.3 and CLDN19 NM_001123395.1 with N-terminal fluorescent tags; the original Q8N6F1-2 supporting identifier is retained without extending the result to all products. The independent human heterodimer evidence in PMID:26446843 refines the gene-level pair in the earlier source row; this exact source/product assertion is retained without treating colocalization, FRET, or an unaligned isoform identifier as a separate stoichiometry measurement.

Summary: Retain the original plasma membrane localization.

Reason: The authentic original abstract identifies paracellin-1 as a renal tight-junction protein. Its full text remains inaccessible, so the curated EXP assertion is retained with that limit and independently corroborated by later human CLDN16 junctional staining. No original figure or assay species is inferred from the abstract.

Summary: Wild-type human claudin-16 reaches the junctional plasma membrane.

Reason: HA-tagged human CLDN16 localizes with ZO-1 at MDCK cell contacts. The T233R comparison instead accumulates in lysosomes; that mutant phenotype does not make lysosomes the normal functional compartment.

Summary: Retain plasma membrane localization of the functional short construct.

Reason: The recovered original Methods and Results distinguish the human construct initiated at the historical second methionine from a longer construct with different trafficking. The active short form localizes to epithelial junctions and changes paracellular permeability; this is not a claim that all historical start-site constructs behave identically.

Summary: Wild-type human claudin-16 is present at epithelial cell junctions.

Reason: The study directly compares wild-type and disease-associated human CLDN16 in MDCK-C7 and other cells. Wild type overlaps junctional ZO-1 and increases magnesium permeability, while variant-specific ER, Golgi and lysosomal retention are separate observations.

Summary: Claudin-16 occupies the junctional membrane in CLDN19-containing complexes.

Reason: Human CLDN16 and CLDN19 localize to epithelial junctions in the reconstituted model. In fibroblasts, CLDN16 alone does not produce strands but is incorporated into strands generated with CLDN19, supporting membrane residence in a partner-dependent structure.

Summary: Retain the observed membrane localization of the tagged human constructs.

Reason: N-terminally fluorescent human CLDN16 is membrane-associated in the cell models; contact enrichment is enhanced by CLDN19. Native mouse and rat TAL staining in the same study is a separate tissue observation, not a direct untagged human tissue assay.

Summary: Retain the inherited plasma membrane compartment.

Reason: The PAINT assertion is consistent with experimentally grounded descendant claudin localization and with direct human CLDN16 junctional assays. CLDN16 performs its channel contribution in this membrane compartment. Target inclusion among the descendants is legitimate and is not treated as circular evidence.

Summary: Retain the combined-method plasma membrane assignment.

Reason: The subcellular-location mapping agrees with direct human CLDN16 localization at epithelial cell contacts. The live ARBA rule is retained as a distinct source component; its historical target-specific route was not reconstructed, so target experiments corroborate the biological compartment rather than proving the original rule execution.

Summary: Claudin-16 acts in bicellular tight junctions.

Reason: Current claudin-family experimental localization supports the curated ancestral compartment, and direct human CLDN16 incorporation into junctional complexes independently establishes the target location. Channel contribution provides a functional basis for the original is_active_in relation.

Summary: Retain the combined ortholog, domain and tight-junction mapping.

Reason: Q925N4 is mouse Cldn16, with experimental junctional evidence. The distinct Ensembl, claudin-domain and subcellular-location components agree with human CLDN16 junctional localization; they are not counted as separate experiments.

Summary: Retain the curated claudin-family junctional localization.

Reason: O88551 is mouse Cldn1 and carries experimental tight-junction annotations. Its paralog identity does not invalidate a conserved family-location transfer; direct human CLDN16 junctional staining and strand incorporation corroborate the target compartment.

Summary: Retain the original renal tight-junction localization.

Reason: The complete authentic original abstract identifies a tight-junction protein involved in renal magnesium resorption. The unread original full text is not used for detailed assay claims; later human CLDN16 localization independently supports this compartment.

Summary: Specify transport through the space between epithelial cells.

Reason: The original intercellular term is broad, whereas CLDN16 contributes to a paracellular junctional route. Later human epithelial permeability assays establish this route directly. GO:0160184 is a more informative description here, without claiming an is_a relationship between the two process terms or changing the original TAS source.

Proposed replacements: paracellular transport

Summary: Replace transmembrane transporter wording with the paracellular channel function.

Reason: GO:0015095 describes magnesium passage across a membrane; CLDN16 contributes a channel through the tight-junction barrier between cells. Positive magnesium permeability is preserved: human CLDN16 increases magnesium flux in MDCK-C7 layers, and dog CLDN16–CLDN19 reconstitution independently supports divalent-cation permeability. The route refinement does not deny magnesium transport or imply an autonomous CLDN16 pore.

Proposed replacements: paracellular tight junction channel activity

Summary: Specify the supported junctional membrane compartment.

Reason: The InterPro membrane assignment is correct but broad. Human CLDN16 localization and partner-dependent strand incorporation justify bicellular tight junction as the more informative compartment while retaining the original source mapping.

Proposed replacements: bicellular tight junction

Summary: Retain the family adhesion inference with explicit partner and calcium-assay limits.

Reason: The preserved mouse Cldn1 donor has experimentally grounded calcium-independent adhesion evidence (PMID:10508613). Target experiments distinguish autonomous adhesion from cooperative junction incorporation: human CLDN16 alone lacks strand formation or trans-contact enrichment, but CLDN16 is immunogold-positive in strands with CLDN19 (PMID:18188451), and both proteins become enriched at cell contacts upon coexpression (PMID:28028216). These positive partner-dependent structural results prevent treating the standalone negative result as evidence against every adhesion contribution. Retain the curated ISS inference as non-core; its calcium-independent specificity remains a family inference, since these target assays did not directly test adhesion after calcium removal.

Summary: Retain magnesium specificity while identifying the paracellular route.

Reason: The original metal-ion transport term permits movement between cells. Direct human CLDN16 assays in MDCK-C7 monolayers measure increased magnesium flux, while dog CLDN16–CLDN19 reconstitution supports divalent-cation preference. Use GO:0015693 to retain the directly supported magnesium cargo and GO:0160184 to specify the between-cell route. These terms describe distinct aspects and neither is an ancestor or descendant of the other; calcium and other cation permeability remain documented in the biological summary. The original TAS assertion and citation are preserved.

Proposed replacements: magnesium ion transport paracellular transport

Summary: The original intracellular-cation homeostasis claim remains unresolved.

Reason: GO:0030003 concerns cation levels within a cell. The accessible original abstract establishes renal magnesium handling but does not settle this intracellular claim, and full-text recovery failed. Later transepithelial permeability measurements do not themselves measure intracellular cation homeostasis. Preserve the TAS assertion as unresolved rather than treating an unread assay as absent.

Summary: The CLDN16 terminal motif binds ZO-1 PDZ domains.

Reason: Wild-type and T233R terminal peptides, in-vitro-translated PDZ domains and peptide competition directly test the interaction. Cellular coimmunoprecipitation and junctional targeting provide complementary context; the measured binding supports the terminal anchoring mechanism.

Summary: Retain the weak CLDN16 cis self-association observed by FRET.

Reason: The human fluorescent CLDN16 constructs show weaker but positive homomeric cis FRET relative to other claudin combinations. This does not establish autonomous strands or trans adhesion. The result is retained alongside the older negative homomeric two-hybrid observation as an assay-dependent distinction, not a universal contradiction.

Summary: Retain the supported family self-association inference.

Reason: The mouse Cldn1 donor has direct experimental self-binding annotations, and human CLDN16 shows weak positive cis FRET in a separate study. Retain the family inference without narrowing it to a fixed dimer stoichiometry or inferring that CLDN16 alone generates junctional strands.

Summary: Retain the directly observed tight-junction location.

Reason: Human HA-CLDN16 colocalizes with ZO-1 at MDCK junctions; loss of terminal PDZ binding changes targeting. The broad tight-junction compartment remains a valid representation of the core location.

Summary: Retain the directly observed tight-junction location.

Reason: The active short human construct is junctionally localized in epithelial cells while the longer historical start-site construct differs in trafficking. The broad tight-junction compartment remains a valid representation of the core location.

Summary: Retain the directly observed tight-junction location.

Reason: Human CLDN16 is localized to junctions in the coexpression system and incorporated into CLDN19-containing strands in fibroblasts. The broad tight-junction compartment remains a valid representation of the core location.

Summary: Retain the ARBA tight-junction assignment.

Reason: The current ARBA00027156 condition set 5 includes the target FunFam 1.20.140.150:FF:000012 and Metazoa, and outputs tight-junction localization. Independent human localization supports the conclusion; the current rule match is not presented as a reconstructed historical run.

Summary: Claudin-16 contributes directly to renal paracellular reabsorption.

Reason: The source is authenticated mouse Cldn16, with experimental renal-absorption and paracellular-transport annotations from PMID:17442678. Human disease genetics and measured epithelial channel activity converge on a renal reabsorption role: CLDN16 contributes the conducting junctional structure rather than being merely a downstream marker of renal function.

Summary: Retain the inherited paracellular transport function.

Reason: The curated node is consistent with rodent Cldn16 transport evidence and direct human epithelial permeability measurements. Target inclusion among the descendants reflects experimental grounding rather than circularity; the route is specifically through the junctional space.

Summary: Retain direct evidence for paracellular ion transport.

Reason: The recovered original Methods and Results use human and mouse CLDN16 constructs in epithelial monolayers, with dilution potentials, ion substitutions and ouabain controls. The active human short form changes junctional cation permeability; these experiments distinguish the paracellular route from transcellular conductance.

Summary: Claudin-16 and claudin-19 jointly alter paracellular selectivity.

Reason: Human CLDN16–CLDN19 coexpression in LLC-PK1 layers produces cation-selective junctions and is tested with ion-permeability measurements and interaction-defective variants. The model-specific sodium/chloride effects are retained without erasing positive magnesium permeability found in other epithelial backgrounds.

Summary: Retain the combined paracellular transport assignment.

Reason: The live ARBA00088093 set 0 matches the target FunFam and Eukaryota and outputs paracellular transport. Mouse Cldn16 has experimental transport grounding; independent human assays confirm the route. The rule, ortholog and Ensembl identifiers remain separate components of the original assertion.

Summary: Retain the curated paracellular tight-junction channel activity.

Reason: The PAINT assertion is grounded in target channel experiments and is consistent with partner-dependent CLDN16–CLDN19 junctional conductance. Its original enables relation remains unchanged; the core synthesis expresses CLDN16 contribution to the assembled channel without claiming a standalone pore.

Summary: Retain the directly assayed junctional channel function.

Reason: The original epithelial expression experiments measure CLDN16-dependent cation permeability and include controls for transcellular conductance. They support the paracellular channel term at the membrane-complex level, without proving an isolated CLDN16-only pore or a universal selectivity ratio.

Summary: Retain the CLDN16–CLDN19 junctional channel function.

Reason: Human coexpression, permeability measurements and interaction/strand assays establish CLDN16 as a functional component of the cation-selective junctional complex. Contributions of CLDN19 and epithelial background remain explicit; the original source relation is preserved.

Summary: Correct the route while preserving magnesium ion transport.

Reason: The electronic inference inherits membrane-crossing wording from GO:0015095. Human CLDN16 expression in MDCK-C7 monolayers instead increases directly measured magnesium flux through the paracellular route (PMID:16528408). GO:0015693 expressly includes magnesium movement between cells, so pairing it with GO:0160184 retains both the transported ion and the junctional route. Neither replacement is an ancestor or descendant of the other. This refines the existing IEA assertion without changing its source identifier or denying positive magnesium permeability.

Proposed replacements: magnesium ion transport paracellular transport