# AGR3 notes

## 2026-06-03 PN Proteostasis review

- Generated inputs with `just fetch-gene human AGR3`; this created the UniProt record, GOA table, and a 10-entry review stub from 38 GOA rows. Falcon deep research completed at `genes/human/AGR3/AGR3-deep-research-falcon.md`.
- PN projection reviewed: `projects/PROTEOSTASIS/reports/pn_projection/pn_projected_annotations.tsv:219` proposes `GO:0003756 protein disulfide isomerase activity` for AGR3 from `ER proteostasis|Folding enzyme|Protein disulfide isomerases`.
- Conservative decision: do not add `GO:0003756` for AGR3. AGR3 is ER-retained and thioredoxin-like, but Falcon synthesis highlights that AGR3 lacks the canonical PDI CXXC/WCXXC motif and "is **not a canonical disulfide isomerase**" [file:human/AGR3/AGR3-deep-research-falcon.md "Although structurally in the PDI/thioredoxin family, AGR3's **DCYQS** motif (lacking the second cysteine) supports the view that AGR3 is **not a canonical disulfide isomerase**"]. This makes the PN projection a family/context projection rather than a safe gene-level GO addition.
- Strongest supported physiological function: ER-localized AGR3 is required for calcium-mediated regulation of airway ciliary beat frequency and mucociliary clearance [PMID:25751668 "AGR3 deficiency had no detectable effects on ciliary beat frequency (CBF) when airways were perfused with a calcium-free solution, suggesting that AGR3 is required for calcium-mediated regulation of ciliary function. Decreased CBF was associated with impaired mucociliary clearance in AGR3-deficient airways."].
- ER localization is supported by the KDEL-receptor/retention motif study [PMID:18086916 "Three of the 16 constructs, ERp18, Hag3, and GP7R, changed their localization from the ER to the Golgi when the putative ER-retention motif was not present"] and by the airway paper's ciliated-cell ER-resident framing [PMID:25751668 "Here we report that AGR3, unlike its closest homolog AGR2, is restricted to ciliated cells in the airway epithelium and is not induced by ER stress."].
- Dystroglycan binding is retained as non-core. The underlying evidence is yeast two-hybrid interaction with alpha-dystroglycan/DAG1 and C4.4a/LYPD3 in a cancer context [PMID:12592373 "Yeast two-hybrid cloning identified metastasis-associated GPI-anchored C4.4a protein and extracellular alpha-dystroglycan (DAG-1) as binding partners for both hAG-2 and hAG-3"], with the authors noting that clinical-context confirmation was still needed [PMID:12592373 "Clearly, further analyses such as coimmunoprecipitation are required to confirm that these interactions occur in clinical cancers"].
- Generic `protein binding` rows from high-throughput interactome maps were marked over-annotated, except the PMID:12592373 row was modified to the more specific existing dystroglycan binding term.