tgrC1

id: P42523
gene_symbol: tgrC1
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:44689
  label: Dictyostelium discoideum
description: TgrC1 (Tiger protein C1; historically named gp150 and LagC/lagC1) is a
  large, heavily N-glycosylated single-pass type I transmembrane cell-surface glycoprotein
  of the social amoeba Dictyostelium discoideum. Its long extracellular region contains
  multiple immunoglobulin-like IPT/TIG domains, a single C-terminal transmembrane
  helix, and a short cytoplasmic tail. TgrC1 is expressed upon starvation from the
  aggregation/post-aggregation stage onward and localizes to the plasma membrane,
  becoming enriched at cell-cell contact regions. It functions as the heterophilic
  ligand for the transmembrane receptor TgrB1 displayed on adjacent cells; TgrC1 forms
  cis-homodimers that bind monomeric TgrB1 in trans, nucleating the assembly of large
  TgrB1-TgrC1 adhesion complexes that mediate EDTA-resistant (calcium-independent)
  cell-cell adhesion during the post-aggregation stages of multicellular development.
  This adhesion is required for progression beyond the loose aggregate stage, tip
  formation, slug and fruiting body morphogenesis, and for prestalk/prespore cell-type
  differentiation. The adjacent tgrB1 and tgrC1 genes share a common promoter and
  are among the most polymorphic loci in the genome; a matching pair of tgrB1 and
  tgrC1 alleles is necessary and sufficient for allorecognition (self/kin recognition),
  making the Tgr locus a polychromatic greenbeard that governs strain segregation
  and cooperative development. TgrC1 acts largely non-cell-autonomously (as a ligand),
  whereas its partner TgrB1 signals cell-autonomously as the receptor.
existing_annotations:
- term:
    id: GO:0098609
    label: cell-cell adhesion
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: Phylogenetic inference of a cell-cell adhesion role is strongly corroborated
      by direct experimental evidence for this gene product; TgrC1/gp150 is a bona
      fide cell adhesion molecule.
    action: ACCEPT
    reason: Cell-cell adhesion is a well-established core role of TgrC1, supported
      by decades of gp150/lagC biochemistry and by TgrB1-TgrC1 binding studies.
    supported_by:
    - reference_id: PMID:1577768
      supporting_text: provide direct evidence that gp150 is a cell-cell adhesion
        molecule involved in cell-cell binding in the postaggregation stage of Dictyostelium
        development
- term:
    id: GO:0009897
    label: external side of plasma membrane
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: TgrC1 is a type I transmembrane protein whose large glycosylated extracellular
      domain (and IPT/TIG binding region) faces outward, where it engages TgrB1 on
      adjacent cells. The external-side location is correct.
    action: ACCEPT
    reason: The functional (ligand) portion of TgrC1 is displayed on the external
      side of the plasma membrane, consistent with its heterophilic trans-binding
      to TgrB1.
    supported_by:
    - reference_id: PMID:23477311
      supporting_text: Both TgrB1 and TgrC1 are type I transmembrane proteins, which
        contain three extracellular IPT/TIG
- term:
    id: GO:0031152
    label: aggregation involved in sorocarp development
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: TgrC1 is expressed at aggregation/post-aggregation and is required for
      progression beyond the loose aggregate stage, so a role within sorocarp aggregation/development
      is correct, but it is a developmental process rather than the core molecular
      function.
    action: KEEP_AS_NON_CORE
    reason: The aggregation/development role is a downstream consequence of TgrC1-mediated
      adhesion and allorecognition; it is retained as a non-core biological process.
    supported_by:
    - reference_id: PMID:7926779
      supporting_text: Mutant cells aggregate normally but are unable to proceed past
        the loose aggregate stage
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Plasma membrane localization is correct and independently established
      by direct experimental evidence for gp150/TgrC1.
    action: ACCEPT
    reason: TgrC1 is a single-pass plasma membrane glycoprotein, consistent with its
      role as a cell-surface adhesion ligand.
    supported_by:
    - reference_id: PMID:11071787
      supporting_text: gp150 is a membrane glycoprotein which has been implicated in
        cell-cell adhesion in the postaggregation stages of Dictyostelium development
- term:
    id: GO:0007165
    label: signal transduction
  evidence_type: IEA
  original_reference_id: GO_REF:0000108
  qualifier: involved_in
  review:
    summary: TgrC1 participates in signaling as the ligand that triggers TgrB1 receptor
      activation, but "signal transduction" is a broad inter-ontology inference. The
      cell-autonomous signaling activity resides in the TgrB1 receptor, whereas TgrC1
      acts non-cell-autonomously as the ligand.
    action: KEEP_AS_NON_CORE
    reason: The general term is not wrong (TgrC1 binding induces TgrB1 phosphorylation
      and downstream signaling) but is non-specific; TgrC1's core molecular role is
      as an adhesion ligand, not as a signal transducer per se.
    supported_by:
    - reference_id: PMID:29038229
      supporting_text: The TgrB1 cytoplasmic tail is essential for its function and
        it becomes phosphorylated upon association with TgrC1
- term:
    id: GO:0070161
    label: anchoring junction
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: This is a UniProt subcellular-location mapping from the "Cell junction"
      keyword. TgrC1 is enriched at cell-cell contacts, and adherens junction-like
      structures have been described in Dictyostelium, consistent with the experimental
      annotations to this term.
    action: ACCEPT
    reason: Enrichment of gp150/TgrC1 at cell-cell junctions/contact sites is documented
      experimentally; this electronic mapping agrees with those annotations and is
      retained as a localization.
    supported_by:
    - reference_id: PMID:15561583
      supporting_text: adherens junction-like structures have been discovered in the
        fruiting body
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: EXP
  original_reference_id: PMID:11071787
  qualifier: located_in
  review:
    summary: Direct experimental localization of gp150/TgrC1 to the membrane and cell-cell
      contact regions.
    action: ACCEPT
    reason: gp150 is directly shown to be a membrane glycoprotein enriched at cell-cell
      contacts, a core plasma membrane localization.
    supported_by:
    - reference_id: PMID:11071787
      supporting_text: Immunolocalization studies have confirmed its enrichment in
        cell-cell contact regions
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: EXP
  original_reference_id: PMID:15561583
  qualifier: located_in
  review:
    summary: Review documenting lagC (gp150) as a developmentally regulated cell adhesion
      molecule at the plasma membrane.
    action: ACCEPT
    reason: Plasma membrane localization of the gp150/lagC adhesion system is well
      established.
    supported_by:
    - reference_id: PMID:15561583
      supporting_text: 'the adhesion genes, cadA (encoding DdCAD-1), csaA (gp80) and
        lagC (gp150)'
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: EXP
  original_reference_id: PMID:1577768
  qualifier: located_in
  review:
    summary: gp150 was purified as a cell surface glycoprotein mediating EDTA-resistant
      cell-cell adhesion.
    action: ACCEPT
    reason: The purified adhesion molecule is a cell-surface/plasma membrane glycoprotein.
    supported_by:
    - reference_id: PMID:1577768
      supporting_text: A cell surface glycoprotein of apparent Mr 150,000 (gp150) has
        been implicated in mediating EDTA-resistant cell-cell adhesion in Dictyostelium
        discoideum
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: EXP
  original_reference_id: PMID:498273
  qualifier: located_in
  review:
    summary: The founding study identifying gp150 as a developmentally regulated cell-surface
      glycoprotein that accumulates on aggregating cells.
    action: ACCEPT
    reason: gp150 accumulates on the cell surface of aggregating cells, a core plasma
      membrane localization.
    supported_by:
    - reference_id: PMID:498273
      supporting_text: there is a rapid accumulation of gp150 on the surfaces of aggregating
        cells
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: EXP
  original_reference_id: PMID:7407916
  qualifier: located_in
  review:
    summary: gp150 was shown by immuno-EM to be closely associated with the plasma
      membrane and enriched at cell contacts.
    action: ACCEPT
    reason: Direct ultrastructural evidence places gp150 at the plasma membrane.
    supported_by:
    - reference_id: PMID:7407916
      supporting_text: gp150 was closely associated with the plasma membrane
- term:
    id: GO:0070161
    label: anchoring junction
  evidence_type: EXP
  original_reference_id: PMID:11071787
  qualifier: located_in
  review:
    summary: gp150/TgrC1 is enriched in cell-cell contact regions, consistent with
      a junction-associated localization.
    action: ACCEPT
    reason: Experimental immunolocalization documents enrichment at cell-cell contact/junction
      regions; retained as a localization, deferring to the curator on the specific
      junction term.
    supported_by:
    - reference_id: PMID:11071787
      supporting_text: Immunolocalization studies have confirmed its enrichment in
        cell-cell contact regions
- term:
    id: GO:0070161
    label: anchoring junction
  evidence_type: EXP
  original_reference_id: PMID:15561583
  qualifier: located_in
  review:
    summary: Adherens junction-like structures were described in the Dictyostelium
      fruiting body, and lagC/gp150 is one of the adhesion systems involved.
    action: ACCEPT
    reason: Junction-associated localization of the lagC/gp150 adhesion system is
      documented; retained as a localization.
    supported_by:
    - reference_id: PMID:15561583
      supporting_text: adherens junction-like structures have been discovered in the
        fruiting body
- term:
    id: GO:0070161
    label: anchoring junction
  evidence_type: EXP
  original_reference_id: PMID:1577768
  qualifier: located_in
  review:
    summary: gp150 mediates cell-cell binding at cell contacts; localization to cell-junction
      regions is consistent with the broader gp150 literature, although this abstract
      emphasizes adhesion rather than junction ultrastructure.
    action: ACCEPT
    reason: Experimental (curator read full text); junction-associated localization
      is consistent with gp150 enrichment at sites of cell contact.
    supported_by:
    - reference_id: PMID:7407916
      supporting_text: we found a distribution gradient of gp150 wherein the concentration
        was enriched at or near sites of cell contact
- term:
    id: GO:0070161
    label: anchoring junction
  evidence_type: EXP
  original_reference_id: PMID:7407916
  qualifier: located_in
  review:
    summary: gp150 is distributed on the cell surface in a nonrandom fashion favoring
      cell junctions/contact sites.
    action: ACCEPT
    reason: Direct evidence for enrichment of gp150 at cell junctions/contact sites.
    supported_by:
    - reference_id: PMID:7407916
      supporting_text: we found a distribution gradient of gp150 wherein the concentration
        was enriched at or near sites of cell contact
- term:
    id: GO:0009642
    label: response to light intensity
  evidence_type: HEP
  original_reference_id: PMID:41057014
  qualifier: acts_upstream_of_or_within
  review:
    summary: This HEP annotation derives from a transcriptomic screen in which tgrC1
      (lagC) mRNA was downregulated under dark relative to light incubation. This
      reflects light-dependent transcriptional regulation of tgrC1, not a function
      of TgrC1 in sensing or mediating a response to light.
    action: MARK_AS_OVER_ANNOTATED
    reason: A change in tgrC1 transcript level with light exposure is a high-throughput,
      expression-based observation; it does not indicate that TgrC1 mediates a response
      to light intensity, and it is far from the protein's core adhesion/ligand function.
    supported_by:
    - reference_id: PMID:41057014
      supporting_text: both of which were downregulated under the dark condition from
        transcriptomic analysis in the unicellular phase
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:23477311
  qualifier: enables
  review:
    summary: The IPI interaction here is with TgrB1, the receptor for which TgrC1
      is the heterophilic ligand. Bare "protein binding" is uninformative; a more
      specific molecular function (receptor ligand activity) captures the biology.
    action: MODIFY
    reason: TgrC1 binds TgrB1 via mutual IPT/TIG domains; since TgrB1 is the receptor
      and TgrC1 the ligand, receptor ligand activity is the informative molecular
      function.
    proposed_replacement_terms:
    - id: GO:0048018
      label: receptor ligand activity
    supported_by:
    - reference_id: PMID:23477311
      supporting_text: far-Western blotting coupled with MS to identify TgrB1 as the
        heterophilic binding partner of TgrC1
- term:
    id: GO:0048018
    label: receptor ligand activity
  evidence_type: IDA
  original_reference_id: PMID:29038229
  qualifier: enables
  review:
    summary: Direct genetic/biochemical evidence that TgrC1 functions as the ligand
      for the TgrB1 receptor in cooperative aggregation and differentiation. This
      is the core molecular function of TgrC1.
    action: ACCEPT
    reason: Merodiploid experiments demonstrate that TgrC1 acts non-cell-autonomously
      as the ligand while TgrB1 is the cell-autonomous receptor.
    supported_by:
    - reference_id: PMID:29038229
      supporting_text: TgrB1 acts as a receptor with TgrC1 as its ligand in cooperative
        aggregation and differentiation
    - reference_id: PMID:29038229
      supporting_text: These non-cell-autonomous phenotypes indicate that TgrC1 functions
        as a ligand and TgrB1 does not
- term:
    id: GO:0005911
    label: cell-cell junction
  evidence_type: IDA
  original_reference_id: PMID:7407916
  qualifier: is_active_in
  review:
    summary: gp150/TgrC1 is enriched at sites of cell contact, where it mediates cell-cell
      adhesion. Cell-cell junction is an appropriate site of action.
    action: ACCEPT
    reason: Direct localization evidence places gp150 at cell-cell junctions/contact
      sites, where its adhesion function operates.
    supported_by:
    - reference_id: PMID:7407916
      supporting_text: we found a distribution gradient of gp150 wherein the concentration
        was enriched at or near sites of cell contact
- term:
    id: GO:0007157
    label: heterophilic cell-cell adhesion
  evidence_type: IDA
  original_reference_id: PMID:23477311
  qualifier: involved_in
  review:
    summary: TgrC1 mediates heterophilic cell-cell adhesion via its interaction with
      the distinct partner TgrB1 through mutual IPT/TIG domains. This is a core role.
    action: ACCEPT
    reason: The adhesion is heterophilic (TgrC1 binds a different protein, TgrB1),
      directly demonstrated by binding and mapping studies.
    supported_by:
    - reference_id: PMID:23477311
      supporting_text: The heterophilic adhesion protein TgrC1 (Tgr is transmembrane,
        IPT, IG, E-set, repeat protein) is expressed during cell aggregation
    - reference_id: PMID:23477311
      supporting_text: we have mapped the cell-binding regions in these two proteins
        to Lys(537)-Ala(783) in TgrB1 and Ile(336)-Val(360) in TgrC1
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: TAS
  original_reference_id: PMID:15261655
  qualifier: is_active_in
  review:
    summary: Plasma membrane site of action is correct for TgrC1; contact-dependent
      adhesion/signaling at the membrane is central to its role, though this particular
      review does not name tgrC1.
    action: ACCEPT
    reason: The plasma membrane location is independently well established for TgrC1;
      the site of action annotation is appropriate.
    supported_by:
    - reference_id: PMID:11071787
      supporting_text: gp150 is a membrane glycoprotein which has been implicated in
        cell-cell adhesion in the postaggregation stages of Dictyostelium development
- term:
    id: GO:0009986
    label: cell surface
  evidence_type: IDA
  original_reference_id: PMID:498273
  qualifier: located_in
  review:
    summary: The original identification of gp150 as a cell-surface glycoprotein that
      accumulates on aggregating cells.
    action: ACCEPT
    reason: Direct cell-surface localization of gp150, consistent with its cell-surface
      adhesion ligand role.
    supported_by:
    - reference_id: PMID:498273
      supporting_text: there is a rapid accumulation of gp150 on the surfaces of aggregating
        cells
- term:
    id: GO:0005911
    label: cell-cell junction
  evidence_type: IDA
  original_reference_id: PMID:11071787
  qualifier: is_active_in
  review:
    summary: gp150/TgrC1 is enriched in cell-cell contact regions, an appropriate
      site of action for its adhesion function.
    action: ACCEPT
    reason: Immunolocalization shows enrichment at cell-cell contacts/junctions.
    supported_by:
    - reference_id: PMID:11071787
      supporting_text: Immunolocalization studies have confirmed its enrichment in
        cell-cell contact regions
- term:
    id: GO:0098635
    label: protein complex involved in cell-cell adhesion
  evidence_type: IDA
  original_reference_id: PMID:24490801
  qualifier: is_active_in
  review:
    summary: TgrC1 is an active unit of the assembled TgrB1-TgrC1 adhesion complex,
      which forms large clusters at cell-cell contacts. This is a core complex membership.
    action: ACCEPT
    reason: TgrC1 homodimers and TgrB1 dimers coalesce into large adhesion complexes
      that mediate cell-cell adhesion.
    supported_by:
    - reference_id: PMID:24490801
      supporting_text: the coalescence of TgrB1-TgrC1 clusters results in the formation
        of large adhesion complexes
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:24490801
  qualifier: enables
  review:
    summary: TgrC1 spontaneously forms cis-homodimers, demonstrated by split-GFP complementation
      and chemical cross-linking. Homodimerization is required to nucleate assembly
      of the adhesion complex.
    action: ACCEPT
    reason: Self-association (identical protein binding) is a genuine and functionally
      important property of TgrC1 that initiates TgrB1-TgrC1 complex assembly.
    supported_by:
    - reference_id: PMID:24490801
      supporting_text: The ability of TgrC1 to form cis-homodimers spontaneously was
        demonstrated by fluorescence complementation studies and confirmed by chemical
        cross-linking
- term:
    id: GO:0007157
    label: heterophilic cell-cell adhesion
  evidence_type: IMP
  original_reference_id: PMID:11071787
  qualifier: involved_in
  review:
    summary: Loss and gain of gp150 function demonstrate that it mediates cell-cell
      adhesion via heterophilic interaction with another (aggregation-stage) component,
      later identified as TgrB1.
    action: ACCEPT
    reason: Mutant/transgenic evidence establishes gp150 as a heterophilic adhesion
      molecule, a core function.
    supported_by:
    - reference_id: PMID:11071787
      supporting_text: gp150 mediates cell-cell adhesion via heterophilic interactions
        with another component that accumulates during the aggregation stage
- term:
    id: GO:0009897
    label: external side of plasma membrane
  evidence_type: IDA
  original_reference_id: PMID:24490801
  qualifier: is_active_in
  review:
    summary: TgrC1 homodimers act on the cell surface, binding TgrB1 in trans across
      the gap between adjacent cells; the ligand-binding region is on the external
      side of the plasma membrane.
    action: ACCEPT
    reason: The functional TgrC1 ectodomain is displayed on the external side of the
      plasma membrane where it engages TgrB1 in trans.
    supported_by:
    - reference_id: PMID:24490801
      supporting_text: the assembly process is initiated upon trans-interaction of
        monomeric TgrB1 with TgrC1 homodimers on adjacent cells
- term:
    id: GO:0009988
    label: cell-cell recognition
  evidence_type: IMP
  original_reference_id: PMID:19285397
  qualifier: involved_in
  review:
    summary: Deletion of the polymorphic lagC1 (tgrC1) causes strain segregation from
      wild-type in chimerae, demonstrating a role in kin/self recognition.
    action: ACCEPT
    reason: TgrC1 is a determinant of cell-cell (kin) recognition, a core organismal
      role tightly linked to its allele-specific adhesion function.
    supported_by:
    - reference_id: PMID:19285397
      supporting_text: Deleting lagB1 and lagC1 results in strain segregation in chimeras
        with wild-type cells
    - reference_id: PMID:19285397
      supporting_text: lagB1 and lagC1 participate in a common self- or kin-recognition
        mechanism in D. discoideum
- term:
    id: GO:0016338
    label: calcium-independent cell-cell adhesion
  evidence_type: IGI
  original_reference_id: PMID:11071787
  qualifier: involved_in
  review:
    summary: gp150/TgrC1 mediates EDTA-resistant (i.e., calcium-independent) cell-cell
      adhesion, distinguishing it from the calcium-dependent DdCAD-1 system.
    action: ACCEPT
    reason: The adhesion mediated by gp150 is EDTA-resistant/calcium-independent, a
      defining property.
    supported_by:
    - reference_id: PMID:11071787
      supporting_text: these cells acquire EDTA-resistant cell-cell binding during
        aggregation
- term:
    id: GO:0097656
    label: cell-cell self recognition
  evidence_type: IGI
  original_reference_id: PMID:21700835
  qualifier: involved_in
  review:
    summary: A matching pair of tgrB1 and tgrC1 alleles is necessary and sufficient
      for attractive self-recognition, mediated by differential cell-cell adhesion.
    action: ACCEPT
    reason: TgrC1 is a direct determinant of self-recognition, established by allele-swap
      genetics.
    supported_by:
    - reference_id: PMID:21700835
      supporting_text: a matching pair of tgrB1 and tgrC1 alleles is necessary and
        sufficient for attractive self-recognition, which is mediated by differential
        cell-cell adhesion
- term:
    id: GO:0099120
    label: socially cooperative development
  evidence_type: IMP
  original_reference_id: PMID:23910661
  qualifier: involved_in
  review:
    summary: The tgrB1/tgrC1 kin-recognition system underlies cooperative multicellular
      development and protects cooperators against cheaters. This is a broad social/developmental
      process downstream of TgrC1's adhesion/recognition function.
    action: KEEP_AS_NON_CORE
    reason: Socially cooperative development is an organismal-level process enabled
      by TgrC1-mediated kin recognition; retained as a non-core biological process.
    supported_by:
    - reference_id: PMID:23910661
      supporting_text: This mechanism is mediated by two transmembrane proteins, TgrB1
        and TgrC1
- term:
    id: GO:0099138
    label: altruistic, chimeric sorocarp development
  evidence_type: IDA
  original_reference_id: PMID:28120827
  qualifier: involved_in
  review:
    summary: The polymorphic Tgr locus (tgrB1/tgrC1) acts as a polychromatic greenbeard
      that determines partner-specific cooperation and segregation in chimeric development.
      This is a high-level social process.
    action: KEEP_AS_NON_CORE
    reason: Altruistic, chimeric sorocarp development is an organismal social outcome
      of TgrC1-mediated allorecognition/adhesion; retained as non-core.
    supported_by:
    - reference_id: PMID:28120827
      supporting_text: a matching pair of tgrB1 and tgrC1 alleles is necessary and
        sufficient for attractive self-recognition and cell-cell adhesion
- term:
    id: GO:0031149
    label: sorocarp stalk cell differentiation
  evidence_type: IGI
  original_reference_id: PMID:25894230
  qualifier: acts_upstream_of_or_within
  review:
    summary: Suppressor genetics show that tgrC1 regulates stalk cell differentiation
      in a cell-autonomous manner, separable from its kin-recognition function. This
      is a downstream developmental role.
    action: KEEP_AS_NON_CORE
    reason: Regulation of stalk differentiation is a downstream developmental consequence
      of TgrC1 function rather than its core molecular activity.
    supported_by:
    - reference_id: PMID:25894230
      supporting_text: tgrC1 regulates stalk differentiation in a cell-autonomous
        manner and spore differentiation in a non-cell-autonomous manner
- term:
    id: GO:0031152
    label: aggregation involved in sorocarp development
  evidence_type: IEP
  original_reference_id: PMID:25887420
  qualifier: acts_upstream_of_or_within
  review:
    summary: Developmental transcriptome profiling places tgrC1 expression at the
      aggregate-to-mound transition, where tgrB1/tgrC1 constitute a checkpoint for
      development beyond aggregation. This is an expression-based (IEP) developmental
      inference.
    action: KEEP_AS_NON_CORE
    reason: The aggregation/development role is a downstream biological process; the
      IEP expression evidence supports timing rather than the core molecular function.
    supported_by:
    - reference_id: PMID:25887420
      supporting_text: In order for D. discoideum to develop beyond the aggregation
        stage into mounds, amoebae must clear a checkpoint established by the allorecognition
        genes tgrB1 and tgrC1
- term:
    id: GO:0098609
    label: cell-cell adhesion
  evidence_type: IDA
  original_reference_id: PMID:1577768
  qualifier: involved_in
  review:
    summary: Purified gp150 directly inhibits post-aggregation cell reassociation
      and binds saturably to cells, providing direct evidence that it is a cell-cell
      adhesion molecule.
    action: ACCEPT
    reason: Core adhesion function directly demonstrated with purified gp150.
    supported_by:
    - reference_id: PMID:1577768
      supporting_text: provide direct evidence that gp150 is a cell-cell adhesion
        molecule involved in cell-cell binding in the postaggregation stage of Dictyostelium
        development
- term:
    id: GO:1902168
    label: response to catechin
  evidence_type: IDA
  original_reference_id: PMID:23516620
  qualifier: involved_in
  review:
    summary: In EGCG-treated cells, tgrC expression is delayed along with other late-aggregate/early-mound
      genes. This reflects a transcriptional/developmental response to catechin, not
      a core molecular function of TgrC1.
    action: KEEP_AS_NON_CORE
    reason: tgrC responds to catechin treatment by delayed expression, a peripheral
      (non-core) response secondary to catechin's block of aggregation and motility.
    supported_by:
    - reference_id: PMID:23516620
      supporting_text: The delays in expression were also observed for tgrC and gbfA,
        genes expressed from late aggregate to early mound stage
- term:
    id: GO:0031152
    label: aggregation involved in sorocarp development
  evidence_type: IMP
  original_reference_id: PMID:7926779
  qualifier: acts_upstream_of_or_within
  review:
    summary: lagC-null cells aggregate but arrest at the loose aggregate stage and
      fail subsequent development, showing lagC/TgrC1 acts within post-aggregation
      sorocarp development.
    action: KEEP_AS_NON_CORE
    reason: The developmental arrest phenotype supports a role within sorocarp development,
      a downstream biological process rather than the core molecular function.
    supported_by:
    - reference_id: PMID:7926779
      supporting_text: lagC- null cells aggregate but then disaggregate and reaggregate
        to form small granular mounds
- term:
    id: GO:0031152
    label: aggregation involved in sorocarp development
  evidence_type: IMP
  original_reference_id: PMID:14651934
  qualifier: acts_upstream_of_or_within
  review:
    summary: lagC is the terminal node of a comC-lagC-lagD cell-adhesion/communication
      pathway required for sporulation, acting within multicellular development.
    action: KEEP_AS_NON_CORE
    reason: Role within the sorocarp developmental/signaling pathway is a downstream
      process; retained as non-core.
    supported_by:
    - reference_id: PMID:14651934
      supporting_text: the cell adhesion gene lagC is the terminal node in this signaling
        network
core_functions:
- description: TgrC1 acts as the heterophilic cell-surface ligand for the TgrB1 receptor
    on adjacent cells. Its glycosylated IPT/TIG ectodomain, displayed on the external
    side of the plasma membrane, binds TgrB1 in trans in an allele-specific manner,
    driving calcium-independent cell-cell adhesion, allorecognition/self-recognition,
    and activation of TgrB1-mediated signaling required for post-aggregative development.
  molecular_function:
    id: GO:0048018
    label: receptor ligand activity
  directly_involved_in:
  - id: GO:0007157
    label: heterophilic cell-cell adhesion
  - id: GO:0009988
    label: cell-cell recognition
  locations:
  - id: GO:0009897
    label: external side of plasma membrane
  - id: GO:0005886
    label: plasma membrane
  supported_by:
  - reference_id: PMID:29038229
    supporting_text: TgrB1 acts as a receptor with TgrC1 as its ligand in cooperative
      aggregation and differentiation
  - reference_id: PMID:29038229
    supporting_text: These non-cell-autonomous phenotypes indicate that TgrC1 functions
      as a ligand and TgrB1 does not
  - reference_id: PMID:23477311
    supporting_text: The heterophilic adhesion protein TgrC1 (Tgr is transmembrane,
      IPT, IG, E-set, repeat protein) is expressed during cell aggregation
- description: TgrC1 self-associates into cis-homodimers on the surface of one cell;
    these homodimers bind monomeric TgrB1 on the neighboring cell and nucleate the
    coalescence of large TgrB1-TgrC1 clusters into the cell-cell adhesion complex.
  molecular_function:
    id: GO:0042802
    label: identical protein binding
  directly_involved_in:
  - id: GO:0098609
    label: cell-cell adhesion
  in_complex:
    id: GO:0098635
    label: protein complex involved in cell-cell adhesion
  locations:
  - id: GO:0009897
    label: external side of plasma membrane
  supported_by:
  - reference_id: PMID:24490801
    supporting_text: The ability of TgrC1 to form cis-homodimers spontaneously was
      demonstrated by fluorescence complementation studies and confirmed by chemical
      cross-linking
  - reference_id: PMID:24490801
    supporting_text: the coalescence of TgrB1-TgrC1 clusters results in the formation
      of large adhesion complexes
references:
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping, accompanied by conservative changes to GO terms applied by
    UniProt
  findings: []
- id: GO_REF:0000108
  title: Automatic assignment of GO terms using logical inference, based on on inter-ontology
    links
  findings: []
- id: PMID:11071787
  title: The membrane glycoprotein gp150 is encoded by the lagC gene and mediates
    cell-cell adhesion by heterophilic binding during Dictyostelium development.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Establishes gp150 = lagC (TgrC1) and demonstrates heterophilic,
      EDTA-resistant cell-cell adhesion with enrichment at cell-cell contacts. Abstract-only
      in cache; claims verified against abstract.
- id: PMID:14651934
  title: A cell-adhesion pathway regulates intercellular communication during Dictyostelium
    development.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Places lagC as the terminal node of a comC-lagC-lagD signaling pathway
      required for sporulation; supports the developmental (non-core) role.
- id: PMID:15261655
  title: Dictyostelium morphogenesis.
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: General morphogenesis review used as TAS support for plasma membrane
      site of action; does not name tgrC1 specifically.
- id: PMID:15561583
  title: Regulation of cell-cell adhesion during Dictyostelium development.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Review of Dictyostelium adhesion systems (cadA, csaA, lagC/gp150)
      noting adherens junction-like structures; supports membrane/junction localization.
- id: PMID:1577768
  title: Purification and partial characterization of a cell adhesion molecule (gp150)
    involved in postaggregation stage cell-cell binding in Dictyostelium discoideum.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Purified gp150 inhibits post-aggregation reassociation and binds
      cells saturably; direct evidence for cell-cell adhesion molecule function.
- id: PMID:19285397
  title: Polymorphic members of the lag gene family mediate kin discrimination in
    Dictyostelium.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Full text available; lagC1 (tgrC1) deletion causes strain segregation
      from wild type, establishing the kin-recognition role.
- id: PMID:21700835
  title: Self-recognition in social amoebae is mediated by allelic pairs of tiger
    genes.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Full text available; matching tgrB1/tgrC1 allele pairs are necessary
      and sufficient for attractive self-recognition via differential adhesion.
- id: PMID:23477311
  title: TgrC1 mediates cell-cell adhesion by interacting with TgrB1 via mutual IPT/TIG
    domains during development of Dictyostelium discoideum.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Identifies TgrB1 as the heterophilic binding partner and maps the
      TgrC1 binding region (Ile336-Val360, TIG2). Abstract-only in cache; claims verified
      against abstract.
- id: PMID:23516620
  title: The green tea catechin epigallocatechin gallate (EGCG) blocks cell motility,
    chemotaxis and development in Dictyostelium discoideum.
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: Full text available; tgrC expression is delayed by EGCG among late-aggregate
      genes. Supports a peripheral response-to-catechin annotation, not a core function.
- id: PMID:23910661
  title: Kin recognition protects cooperators against cheaters.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Full text available; uses tgrB1/tgrC1 allele swaps to show kin recognition
      protects cooperators; supports the socially cooperative development (non-core)
      role.
- id: PMID:24490801
  title: Assembly of the TgrB1-TgrC1 cell adhesion complex during Dictyostelium discoideum
    development.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Demonstrates TgrC1 cis-homodimerization and the assembly of large
      TgrB1-TgrC1 adhesion complexes. Abstract-only in cache; claims verified against
      abstract.
- id: PMID:25887420
  title: Leaps and lulls in the developmental transcriptome of Dictyostelium discoideum.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Full text available; positions tgrB1/tgrC1 as an aggregate-to-mound
      developmental checkpoint; supports the IEP timing/developmental annotation.
- id: PMID:25894230
  title: TgrC1 Has Distinct Functions in Dictyostelium Development and Allorecognition.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Full text available; suppressor genetics separate TgrC1's cell-autonomous
      stalk-differentiation role from its non-cell-autonomous spore and recognition
      roles.
- id: PMID:28120827
  title: A polychromatic 'greenbeard' locus determines patterns of cooperation in
    a social amoeba.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Full text available; the tgrB1/tgrC1 locus is a polychromatic greenbeard
      whose binding strength predicts partner-specific segregation.
- id: PMID:29038229
  title: The polymorphic proteins TgrB1 and TgrC1 function as a ligand-receptor pair
    in Dictyostelium allorecognition.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Full text available; merodiploid experiments establish TgrC1 as
      the non-cell-autonomous ligand and TgrB1 as the cell-autonomous receptor. Key
      support for the core receptor-ligand activity.
- id: PMID:41057014
  title: Transcriptomic and metabolomic insights into light-mediated unicellular-to-multicellular
    transition in Dictyostelium discoideum.
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: Full text available; tgrC1 (lagC) is downregulated under dark in
      a transcriptomic screen. This is expression-based and does not indicate a TgrC1
      function in light response (basis for the over-annotation call).
- id: PMID:498273
  title: Identification of a cell surface glycoprotein involved in cell aggregation
    in D. discoideum.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Founding study identifying gp150 as a developmentally regulated
      cell-surface glycoprotein whose antibodies block reaggregation.
- id: PMID:7407916
  title: A glycoprotein involved in aggregation of D. discoideum is distributed on
    the cell surface in a nonrandom fashion favoring cell junctions.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Immuno-EM shows gp150 is closely associated with the plasma membrane
      and enriched at cell-cell contact/junction sites.
- id: PMID:7926779
  title: LagC is required for cell-cell interactions that are essential for cell-type
    differentiation in Dictyostelium.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Identifies lagC and shows null cells arrest at the loose aggregate
      stage with defective cell-type differentiation and sporulation.