VIN1 (vinculin, Oscarella pearsei, UniProt A0A3B6UES5) -- review notes

Automated deep research was unavailable for this gene (no deep-research provider
keys in this environment). These notes were written manually from the cached full
text of the single primary paper (PMID:29880641, Miller et al. 2018 J Biol Chem)
and the UniProt Swiss-Prot entry (VINC_OSCPE). No other literature on this protein
is known to exist.

Identity and structure

• 846 aa member of the vinculin/alpha-catenin (VIN) family; groups with animal
  vinculins in phylogeny, but lacks domain D2 that is typical of vinculins
  PMID:29880641.
• O. pearsei has three VIN-family proteins: vinculin, alpha-catenin and an
  "uncharacterized" clade member
  PMID:29880641.
• Crystal structure 2.3 A (PDB 6BFI); overall more vinculin-like than
  alpha-catenin-like; monomer by SEC-MALS
  PMID:29880641.

Biochemistry (recombinant protein, in vitro)

• ITC: full-length VIN1 and its D1 domain (1-257) bind a synthetic Op talin
  vinculin-binding-site peptide (TLN residues 598-621), but not an Op beta-catenin
  peptide PMID:29880641;
  PMID:29880641.
  D1 binds with Kd ~82 nM, full length ~1.1 uM, i.e. partial autoinhibition.
• F-actin co-sedimentation: VIN1 alone does not bind F-actin, but does so in the
  presence of talin peptide
  PMID:29880641;
  PMID:29880641.
  Note: rabbit skeletal muscle actin was used.
• Beta-catenin was the only alpha-catenin-type partner tested; it did not bind.
  Alpha-catenin, cadherin and integrin binding were not tested.

Localization (endogenous protein in sponge tissue -- NOT heterologous expression)

• Affinity-purified antibody against Op vinculin, validated by Western blot,
  antigen competition and IP; immunostaining of fixed O. pearsei tissue
  (pinacoderm, choanoderm), co-stained with phalloidin.
• Four patterns: belt-like zone at cell-cell contacts in pinacoderm;
  filopodial/lamellipodial extensions of motile mesohyl cells; base of the
  microvillar collar of choanocytes plus belt at cell-cell contacts in choanoderm;
  cytoplasmic signal in pinacoderm
  PMID:29880641;
  PMID:29880641;
  PMID:29880641.
• Co-localizes with F-actin in every context
  PMID:29880641.
• Junctions are not ultrastructurally defined
  PMID:29880641.
• The "cell-ECM contact" interpretation is inferred from filopodial localization in
  migratory cells; no integrin/talin co-staining was done.

Curation decisions (summary)

• protein binding IPI (with TLN) -> MODIFY to talin binding GO:1990147.
• actin filament binding IDA -> ACCEPT (talin-dependent, autoinhibited alone).
• filopodium / cortical cytoskeleton IDA -> ACCEPT (endogenous sponge tissue).
• NEW cell-cell junction (GO:0005911) IDA from the belt-like cell-cell contact
  staining; caveat that the junction type is not defined ultrastructurally.
• No NEW process terms: function in cell adhesion is proposed, not tested
  (no genetic perturbation in sponges).