PIK3CD curation notes

2026-05-12 Falcon integration

Generated Falcon deep research at PIK3CD-deep-research-falcon.md and used it with
UniProt plus cached publications to complete the initialized GO review.

Core synthesis: PIK3CD encodes p110delta, a leukocyte-enriched class IA PI3K
catalytic subunit. The central molecular function is PI(4,5)P2 3-kinase
activity producing PIP3 in p85-family regulatory complexes at receptor-activated
membranes. Falcon summarizes this as: [file:human/PIK3CD/PIK3CD-deep-research-falcon.md
"PIK3CD encodes the catalytic subunit p110δ of class IA phosphoinositide
3-kinase (PI3Kδ), a lipid kinase that produces PI(3,4,5)P3 (PIP3) at
membranes downstream of receptor signaling in immune cells, particularly in
lymphocytes."] Direct biochemical work also reports that recombinant p110delta
phosphorylates phosphatidylinositol and associates with p85 PMID:9235916.

The most informative process terms are PI3K/AKT signaling plus immune receptor
contexts, especially BCR, TCR, and CD28. Falcon frames the receptor context as
[file:human/PIK3CD/PIK3CD-deep-research-falcon.md "In immune cells, class IA PI3K
(including p110δ) propagates signaling downstream of BCR, TCR, CD28, ICOS,
CD19, BAFF-R, CD40"] and UniProt separately records BCR and TCR requirements
[file:human/PIK3CD/PIK3CD-uniprot.txt "Required for B-cell receptor (BCR) signaling."]
[file:human/PIK3CD/PIK3CD-uniprot.txt "Required for T-cell receptor (TCR) signaling."].

Broad immune, chemotaxis, endothelial migration, angiogenesis, mast-cell,
neutrophil, NK-cell, and cytokine-production annotations were retained as
non-core where supported. The main evidence is that PI3Kdelta participates in
multiple leukocyte outputs PMID:20940048 and myeloid
activities PMID:20940048.

Several terms were deliberately modified or marked over-annotated:

• Generic PI3K complex was modified to class IA PI3K complex.
• Generic kinase/transferase/nucleotide-binding terms were narrowed toward ATP
  binding or PI(4,5)P2 3-kinase activity.
• PI3P biosynthetic process was modified because that term implies class
  III/VPS34-like biology; PIK3CD is primarily a PIP3-producing class IA kinase.
• Protein binding was marked over-annotated because complex membership and lipid
  kinase activity are the informative annotations.
• Protein phosphorylation was modified because PMID:9113989 supports lipid
  substrate specificity and says p110delta does not phosphorylate p85
  PMID:9113989.