PI3K/Akt/mTOR · target hub

PIK3R3

Phosphoinositide 3-kinase regulatory subunit 3 (p55γ)

PIK3R3 encodes p55γ, a shorter regulatory subunit lacking SH2 domains that assembles with p110 catalytic partners to tune membrane targeting and signaling amplitude; it parallels p85-family modules in neuronal, endocrine, and hematopoietic contexts. Functional studies should consider competitive assembly with PIK3R1/R2 and tissue-specific expression.

Research notes

  • Pair with p85α/β co-IP or KD matrices to compare membrane recruitment.
  • Annotate splice isoforms via HGNC/UniProt before antibody mapping.
  • In immune signaling, cross-read with PIK3CD/PIK3CG modules.

On the pathway hub (sections)

Genetic lesions & expression context (quick reference)

Type / exampleDomain / context (brief)
Expression contextTissue/cell-type–dependent expression
Rare variantsSporadic variants—require functional validation
Pathway couplingCo-occurs with neighboring nodes on the hub

Naming and prevalence vary by cohort and assay—annotate clinically with COSMIC, ClinVar, OncoKB, and datasheets; research context only.

Assay readouts for PIK3R3

  • Lipid side: PIP₃/PI(3,4)P₂ probes or PH-domain pulldowns—separate PIK3R3 from class II/III compartments.
  • Biochemistry: IP–kinase or membrane recruitment; co-IP regulatory partners.
  • Downstream: p-AKT Thr308/Ser473, p-S6K, p-4E-BP1—pair totals and inhibitor titrations.
  • Genetics: PTEN/INPP4 status; NGS/ddPCR for lesions and copy number.

PIK3R3 experimental notes

Examples below reflect common literature and public resources (e.g., CCLE, DepMap)—validate genotypes, expression, and passage in your own stocks before committing assays.

[1] Cell lines commonly used for PIK3R3 studies (examples)

  • Tool lines: HEK293T, MCF-7, HCT116, Jurkat, U937—screen by PIK3R3 expression and pathway context (CCLE/DepMap).
  • Combine with neighbors (PIK3CA, PIK3CB, PIK3CD, PIK3CG) via KD/pharmacology to test non-redundancy.
  • Overexpression/rescue in HEK293T supports mechanism and IP workflows.
  • Isogenic/CRISPR models separate pathway dependency from bypass survival.

[2] Cell samples for PIK3R3 Western blot

  • Whole-cell lysates—optimize RIPA/NP-40 per antibody; phosphatase inhibitors for phospho blots.
  • Stimulation: serum starvation ± insulin/EGF or amino-acid withdrawal/refeed as relevant.
  • Controls: siRNA/shRNA, CRISPR KO, or inhibitors to validate band specificity.
  • Loading: BCA normalization; subcellular fractionation when needed.

[3] Tissue samples for PIK3R3 Western blot

  • Matched tumor/adjacent frozen tissues after pathology review.
  • Mouse GEMM or xenografts—mind species antibody cross-reactivity.
  • Primary cells/PDCs when ethically approved.
  • FFPE needs specialized extraction; frozen tissue preferred for phospho work.

[4] Cell samples for PIK3R3 immunoprecipitation

  • Tagged overexpression: HEK293T FLAG/HA-PIK3R3 for complex capture.
  • Endogenous IP: high-expression lines; often ≥1–5×10⁶ cells per IP.
  • Stimulation: ligand or nutrient treatments enrich interactions—pilot time courses.
  • Controls: isotype IgG, empty vector, KD/KO negatives.

Human tissues and primary cells require ethics/IRB approval; tumors are heterogeneous—record histotype, site, and preservation conditions.

Bypass & related pathways

Models & genetics note

Overexpression vs endogenous PIK3R3 can differ in dosage, splicing, and compartmentation—in organoids/PDX, record passage, matrix, and drug history.

Quick search presets

PIK3R3-related antibodies (keyword-biased)

Adds PIK3R3 keyword bias atop the PI3K/Akt/mTOR antibody pool—if sparse, use presets above or global search.

FAQ

This content supports research reagents and pathway education—not medical advice. Annotate mutations, drug indications, and protocols with authoritative databases, datasheets, and institutional oversight.

Last reviewed: 2026-05-18

Related on this site

See the PI3K/Akt/mTOR hub for neighboring nodes and assay guidance—cross-check MAPK, RTK, metabolism, and autophagy pages as needed.