Seroatlas · Human Serome Atlas

PIK3R3

Phosphatidylinositol 3-kinase regulatory subunit gamma

Also known as: p55, P55G_HUMAN

Cross-references: UniProt · Ensembl · Human Protein Atlas · GeneCards · NCBI Gene

Protein identityUniProt · HPA

UniProt accession
Q92569
Gene
PIK3R3
Ensembl
ENSG00000117461
Chromosome
1
Canonical length
461 aa
Protein class
Cancer-related genes, Metabolic proteins, Predicted intracellular proteins, RAS pathway related proteins
Subcellular location
Nucleoplasm,Cytosol,Connecting piece,Mid piece,Principal piece,End piece

OverviewNCBI Gene

Phosphatidylinositol 3-kinase (PI3K) phosphorylates phosphatidylinositol and similar compounds, which then serve as second messengers in growth signaling pathways. PI3K is composed of a catalytic and a regulatory subunit. The protein encoded by this gene represents a regulatory subunit of PI3K. The encoded protein contains two SH2 domains through which it binds activated protein tyrosine kinases to regulate their activity. [provided by RefSeq, Jun 2016]

Canonical amino-acid sequenceUniProt

461 residues, UniProt reviewed canonical sequence.

>Q92569|PIK3R3
     1  MYNTVWSMDR DDADWREVMM PYSTELIFYI EMDPPALPPK PPKPMTSAVP NGMKDSSVSL
    61  QDAEWYWGDI SREEVNDKLR DMPDGTFLVR DASTKMQGDY TLTLRKGGNN KLIKIYHRDG
   121  KYGFSDPLTF NSVVELINHY HHESLAQYNP KLDVKLMYPV SRYQQDQLVK EDNIDAVGKK
   181  LQEYHSQYQE KSKEYDRLYE EYTRTSQEIQ MKRTAIEAFN ETIKIFEEQC HTQEQHSKEY
   241  IERFRREGNE KEIERIMMNY DKLKSRLGEI HDSKMRLEQD LKNQALDNRE IDKKMNSIKP
   301  DLIQLRKIRD QHLVWLNHKG VRQKRLNVWL GIKNEDADEN YFINEEDENL PHYDEKTWFV
   361  EDINRVQAED LLYGKPDGAF LIRESSKKGC YACSVVADGE VKHCVIYSTA RGYGFAEPYN
   421  LYSSLKELVL HYQQTSLVQH NDSLNVRLAY PVHAQMPSLC R

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against PIK3R3 can act on the native protein depends on physical access: surface and secreted proteins are reachable by circulating antibodies, intracellular proteins usually are not.

Antibody reachability
Intracellular
Secreted
No
Transmembrane segments
0
Mean surface accessibility (rSASA)
0.38
Highest tissue expression
45 nTPM

Expression across tissuesHPA

Tissue

  • cerebellum: 45 nTPM
  • heart muscle: 34 nTPM
  • adipose tissue: 30 nTPM
  • breast: 27 nTPM
  • testis: 24 nTPM
  • lung: 18 nTPM

Single-cell type

  • conjunctival goblet cells: 72 nCPM
  • vascular endothelial cells: 69 nCPM
  • salivary duct cells: 45 nCPM
  • respiratory secretory cells: 30 nCPM
  • kupffer cells: 29 nCPM
  • respiratory deuterosomal cells: 28 nCPM

Immune cell

  • eosinophil: 5.8 nTPM
  • non-classical monocyte: 2.4 nTPM
  • T-reg: 2.3 nTPM
  • gdT-cell: 2 nTPM
  • MAIT T-cell: 1.9 nTPM
  • memory CD8 T-cell: 1.8 nTPM

Brain region

  • cerebellum: 71 nTPM
  • midbrain: 32 nTPM
  • pons: 31 nTPM
  • thalamus: 30 nTPM
  • spinal cord: 29 nTPM
  • medulla oblongata: 28 nTPM

Genetic constraint and essentialitygnomAD · DepMap

Does the body need this protein intact? Low LOEUF or a strong DepMap dependency means loss or blockade of the protein is likely to be felt.

gnomAD LOEUF (loss-of-function intolerance)
1
gnomAD pLI
0
gnomAD missense Z
0.04
DepMap mean gene effect
0.01
DepMap dependency class
selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 5% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Molecular functions

Cellular components

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of PIK3R3 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads PIK3R3 as an antibody target. Whether an autoantibody or antibody against PIK3R3 could matter depends on whether native PIK3R3 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

PIK3R3 is annotated as predominantly intracellular. Intracellular proteins are common autoantibody markers, becoming visible to the immune system after cell injury or altered processing, but are usually markers of disease rather than direct drivers.

Annotation status

The present source text does not explicitly label PIK3R3 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

Canonical record: https://seroatlas.com/gene/PIK3R3. Study-independent annotations aggregated from UniProt, Human Protein Atlas, PubMed, IEDB, Pfam, InterPro, Gene Ontology, AlphaFold, gnomAD, DepMap, ClinVar, TCGA. Catalog release seroatlas-reviewed-human-uniprot-20260313.

Seroatlas is the reference for exploring autoantibody and antibody serology at the human-protein level: the autoreactome and human serome, multiplex serology (HuProt, HuScan, VirScan, PhIP-Seq).

© 2026 · Seroatlas, Discover Oregon LLC · Terms of use

Loading the interactive Seroatlas protein explorer...