Seroatlas · Human Serome Atlas

PIK3R1

Phosphatidylinositol 3-kinase regulatory subunit alpha

Also known as: GRB1, p85, p85-ALPHA, P85A_HUMAN

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

Protein identityUniProt · HPA

UniProt accession
P27986
Gene
PIK3R1
Ensembl
ENSG00000145675
Chromosome
5
Canonical length
724 aa
Protein class
Cancer-related genes, Disease related genes, Human disease related genes, Metabolic proteins, Plasma proteins, Predicted intracellular proteins, RAS pathway related proteins
Subcellular location
Cytosol

OverviewNCBI Gene

Phosphatidylinositol 3-kinase phosphorylates the inositol ring of phosphatidylinositol at the 3-prime position. The enzyme comprises a 110 kD catalytic subunit and a regulatory subunit of either 85, 55, or 50 kD. This gene encodes the 85 kD regulatory subunit. Phosphatidylinositol 3-kinase plays an important role in the metabolic actions of insulin, and a mutation in this gene has been associated with insulin resistance. Alternative splicing of this gene results in four transcript variants encoding different isoforms. [provided by RefSeq, Jun 2011]

Canonical amino-acid sequenceUniProt

724 residues, UniProt reviewed canonical sequence.

>P27986|PIK3R1
     1  MSAEGYQYRA LYDYKKEREE DIDLHLGDIL TVNKGSLVAL GFSDGQEARP EEIGWLNGYN
    61  ETTGERGDFP GTYVEYIGRK KISPPTPKPR PPRPLPVAPG SSKTEADVEQ QALTLPDLAE
   121  QFAPPDIAPP LLIKLVEAIE KKGLECSTLY RTQSSSNLAE LRQLLDCDTP SVDLEMIDVH
   181  VLADAFKRYL LDLPNPVIPA AVYSEMISLA PEVQSSEEYI QLLKKLIRSP SIPHQYWLTL
   241  QYLLKHFFKL SQTSSKNLLN ARVLSEIFSP MLFRFSAASS DNTENLIKVI EILISTEWNE
   301  RQPAPALPPK PPKPTTVANN GMNNNMSLQD AEWYWGDISR EEVNEKLRDT ADGTFLVRDA
   361  STKMHGDYTL TLRKGGNNKL IKIFHRDGKY GFSDPLTFSS VVELINHYRN ESLAQYNPKL
   421  DVKLLYPVSK YQQDQVVKED NIEAVGKKLH EYNTQFQEKS REYDRLYEEY TRTSQEIQMK
   481  RTAIEAFNET IKIFEEQCQT QERYSKEYIE KFKREGNEKE IQRIMHNYDK LKSRISEIID
   541  SRRRLEEDLK KQAAEYREID KRMNSIKPDL IQLRKTRDQY LMWLTQKGVR QKKLNEWLGN
   601  ENTEDQYSLV EDDEDLPHHD EKTWNVGSSN RNKAENLLRG KRDGTFLVRE SSKQGCYACS
   661  VVVDGEVKHC VINKTATGYG FAEPYNLYSS LKELVLHYQH TSLVQHNDSL NVTLAYPVYA
   721  QQRR

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against PIK3R1 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
Cell surface
Secreted
No
Transmembrane segments
0
Mean surface accessibility (rSASA)
0.33
Highest tissue expression
117 nTPM

Expression across tissuesHPA

Tissue

  • bone marrow: 117 nTPM
  • liver: 101 nTPM
  • breast: 91 nTPM
  • heart muscle: 73 nTPM
  • cerebral cortex: 73 nTPM
  • smooth muscle: 70 nTPM

Single-cell type

  • thymic myoid cells: 775 nCPM
  • nk-cells: 628 nCPM
  • oligodendrocyte progenitor cells: 579 nCPM
  • schwann cells: 571 nCPM
  • fibro-adipogenic progenitors: 480 nCPM
  • t-cells: 470 nCPM

Immune cell

  • basophil: 24 nTPM
  • naive CD4 T-cell: 17 nTPM
  • MAIT T-cell: 14 nTPM
  • memory CD4 T-cell: 14 nTPM
  • eosinophil: 13 nTPM
  • naive CD8 T-cell: 12 nTPM

Brain region

  • cerebral cortex: 230 nTPM
  • white matter: 170 nTPM
  • basal ganglia: 167 nTPM
  • midbrain: 150 nTPM
  • thalamus: 143 nTPM
  • amygdala: 131 nTPM

DiseaseUniProt · ClinVar · IEDB · PubMed

Four sources answering four different questions about PIK3R1.

Disease | AllUniProt

Conditions PIK3R1 is implicated in, by any mechanism.

  • Agammaglobulinemia 7, autosomal recessive (AGM7) MIM:615214
  • SHORT syndrome (SHORTS) MIM:269880
  • Immunodeficiency 36 with lymphoproliferation (IMD36) MIM:616005

Disease | GeneticClinVar

78 pathogenic / likely-pathogenic of 755 ClinVar records.

Conditions with pathogenic or likely-pathogenic variants.

  • SHORT syndrome
  • Immunodeficiency 36 with lymphoproliferation
  • Agammaglobulinemia 7, autosomal recessive
  • Vascular malformation
  • Vascular Malformations and Overgrowth

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)
0.23
gnomAD pLI
1
gnomAD missense Z
2.72
DepMap mean gene effect
-0.03
DepMap dependency class
selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 3% 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 PIK3R1 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 PIK3R1 as an antibody target. Whether an autoantibody or antibody against PIK3R1 could matter depends on whether native PIK3R1 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

PIK3R1 is annotated at the cell surface, where native PIK3R1 is exposed to circulating antibodies and is a prime autoantibody target that could block, deplete, or overstimulate it.

Annotation status

The present source text does not explicitly label PIK3R1 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

Canonical record: https://seroatlas.com/gene/PIK3R1. 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...