PI3K/Akt/mTOR · target hub

PIK3C3

Phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3)

PIK3C3 is a PI3K lipid kinase / regulatory module on the PI3K/Akt/mTOR axis. Catalytic subunit of the PI3K complex that mediates formation of phosphatidylinositol 3-phosphate; different complex forms are believed to play a role in multiple membrane trafficking pathways: PI3KC3-C1 is involved in initiation of autophagosomes and PI3KC3-C2 in maturation of a… It is indexed under "Class III PI3K (Vps34 complex; autophagy/endosome crosstalk)" on our pathway page for antibodies, inhibitors, and assay guidance.

Search: PIK3C3Back to pathway overviewUniProt (Q8NEB9)

Research notes

  • Combine with other genes in the same hub block via genetics or pharmacology to test non-redundant roles of PIK3C3.
  • Annotate PIK3CA/PTEN and upstream RTK–Ras context when reading p-AKT, mTORC1/2, or lipid outputs.
  • Verify antibody clone, phospho-site, and stimulation; include KD/KO or inhibitor controls.

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 PIK3C3

  • Lipid side: PIP₃/PI(3,4)P₂ probes or PH-domain pulldowns—separate PIK3C3 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.

PIK3C3 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 PIK3C3 studies (examples)

  • Tool lines: HEK293T, MCF-7, HCT116, Jurkat, U937—screen by PIK3C3 expression and pathway context (CCLE/DepMap).
  • Combine with neighbors (VPS15, NRBF2, BECN1, ATG14) 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 PIK3C3 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 PIK3C3 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 PIK3C3 immunoprecipitation

  • Tagged overexpression: HEK293T FLAG/HA-PIK3C3 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.

Protein reference · sequence & PTMs

Cross-species sequence conservation (vs human)

SpeciesUniProtLengthIdentity vs human
Human (Homo sapiens)Q8NEB9887
100%
Mouse (Mus musculus)Q6PF93887
98.0%
Rat (Rattus norvegicus)O88763887
98.1%
Pig (Sus scrofa)Q5D891887
98.5%
Chicken (Gallus gallus)A0A3Q2UEL4886
94.1%
Frog (Xenopus laevis)Q6AZN6886
92.0%
Zebrafish (Danio rerio)A0A8M9QGZ6887
86.5%
Fruit fly (D. melanogaster)Q9W1M7949
56.7%
Nematode (C. elegans)Q9TXI7901
40.0%
Yeast (S. cerevisiae)P22543875
38.5%

Percent identity vs human UniProt Q8NEB9 from a global (Needleman–Wunsch) alignment. Chicken, zebrafish, and fly rows use unreviewed UniProt entries—confirm site numbering and function per accession and literature.

Protein sequence (human)

Homo sapiensQ8NEB9887 aa

Domain map (UniProt)

L29L34L132T159T163S165S244S249S261S282M617T668T677L771L840L845
  • C2 (PI3K-type) 35–184
  • PIK helical 283–520
  • PI3K/PI4K catalytic 605–871
  • Key loops / regions
  • PTM sites (dot / chip → table)
        10        20        30        40        50        60
MGEAEKFHYIYSCDLDINVQLKIGSLEGKREQKSYKAVLEDPMLKFSGLYQETCSDLYVT
        70        80        90       100       110       120
CQVFAEGKPLALPVRTSYKAFSTRWNWNEWLKLPVKYPDLPRNAQVALTIWDVYGPGKAV
       130       140       150       160       170       180
PVGGTTVSLFGKYGMFRQGMHDLKVWPNVEADGSEPTKTPGRTSSTLSEDQMSRLAKLTK
       190       200       210       220       230       240
AHRQGHMVKVDWLDRLTFREIEMINESEKRSSNFMYLMVEFRCVKCDDKEYGIVYYEKDG
       250       260       270       280       290       300
DESSPILTSFELVKVPDPQMSMENLVESKHHKLARSLRSGPSDHDLKPNAATRDQLNIIV
       310       320       330       340       350       360
SYPPTKQLTYEEQDLVWKFRYYLTNQEKALTKFLKCVNWDLPQEAKQALELLGKWKPMDV
       370       380       390       400       410       420
EDSLELLSSHYTNPTVRRYAVARLRQADDEDLLMYLLQLVQALKYENFDDIKNGLEPTKK
       430       440       450       460       470       480
DSQSSVSENVSNSGINSAEIDSSQIITSPLPSVSSPPPASKTKEVPDGENLEQDLCTFLI
       490       500       510       520       530       540
SRACKNSTLANYLYWYVIVECEDQDTQQRDPKTHEMYLNVMRRFSQALLKGDKSVRVMRS
       550       560       570       580       590       600
LLAAQQTFVDRLVHLMKAVQRESGNRKKKNERLQALLGDNEKMNLSDVELIPLPLEPQVK
       610       620       630       640       650       660
IRGIIPETATLFKSALMPAQLFFKTEDGGKYPVIFKHGDDLRQDQLILQIISLMDKLLRK
       670       680       690       700       710       720
ENLDLKLTPYKVLATSTKHGFMQFIQSVPVAEVLDTEGSIQNFFRKYAPSENGPNGISAE
       730       740       750       760       770       780
VMDTYVKSCAGYCVITYILGVGDRHLDNLLLTKTGKLFHIDFGYILGRDPKPLPPPMKLN
       790       800       810       820       830       840
KEMVEGMGGTQSEQYQEFRKQCYTAFLHLRRYSNLILNLFSLMVDANIPDIALEPDKTVK
       850       860       870       880       
KVQDKFRLDLSDEEAVHYMQSLIDESVHALFAAVVEQIHKFAQYWRK

Canonical isoform (UniProt Q8NEB9); single-letter amino acids. Check UniProt for splice isoforms and sequence conflicts.

Post-translational modifications (phospho & others)

SiteModificationNotes
Phosphorylation10
Thr159Phosphorylation (pThr)

By CDK1/CDK5; impairs Beclin-1 binding and lipid kinase activity—mitotic repression of autophagy (PubMed:20513426).

Thr163Phosphorylation (pThr)

By AMPK; with Ser165, inhibits non-autophagic VPS34 complexes under energy stress. UniProt-curated.

Ser165Phosphorylation (pSer)

By AMPK; inhibitory partner of Thr163. UniProt-curated.

Ser244Phosphorylation (pSer)

UniProt-curated (by similarity); frequent in phosphoproteomics.

Ser249Phosphorylation (pSer)

By ULK1/2/3 (dbPTM/PhosphoSitePlus); upstream mark in autophagy initiation contexts.

Ser261Phosphorylation (pSer)

UniProt / large-scale analysis (e.g. PubMed:19369195).

Ser282Phosphorylation (pSer)

UniProt / large-scale analysis (e.g. PubMed:23186163).

Thr668Phosphorylation (pThr)

By CDK5 near the catalytic domain; can directly suppress activity (PubMed:20513426).

Thr677Phosphorylation (pThr)

PKD (PRKD1) site in the catalytic domain; promotes PI3P and autophagosome formation (PubMed:22095288).

Tyr (Src)Tyrosine phosphorylation

Src-family tyrosine phosphorylation can boost lipid kinase activity (e.g. insulin context; PubMed:24582588)—confirm exact tyrosines per system.

Other modifications4
Lys29 / Lys771（主）；Lys34 / Lys132 等Acetylation

Functional work centers on EP300/p300 acetylation at Lys29 and Lys771 (Mol Cell 2017, PubMed:28844862): Ac-K29 hinders VPS34–Beclin 1 core assembly; Ac-K771 lowers PI substrate affinity. Lys34/Lys132 and others are mostly dbPTM/HTP. No commercial site-specific anti-Ac-K29/K771–VPS34 Abs found.

Detection: Literature: pan–acetyl-lysine Ab on VPS34 IPs (WB); site ID by LC-MS/MS; function via K→R mutants.

Lys (polyUb)Ubiquitination

UBE3C K29/K48 chains promote degradation; ZRANB1/TRABID deubiquitination stabilizes (PubMed:33637724). Cul3–KLHL20 ubiquitinates phagophore VPS34 to terminate autophagy (PubMed:26687681).

Lys840（主）/ Lys845Sumoylation

Lys840 is SUMO1-conjugated via KAP1, promoting acetylated HSP70 / Beclin 1 engagement and autophagy (PNAS 2013, doi:10.1073/pnas.1217692110). Lys845 is largely a secondary db annotation. No commercial site-specific anti-SUMO-K840–VPS34 Ab found.

Detection: Literature: anti-SUMO1 (e.g. Invitrogen) + anti-Vps34 (e.g. Echelon) co-IP/WB or IF; His-SUMO1 pull-downs; site mapped by MS and validated with K840R.

Met617Methionine sulfoxidation

dbPTM Met sulfoxide site backed by redox proteomics (MCP 2011, PubMed:21406390: quantitative MetO map in H₂O₂-stressed Jurkat cells)—not a site-specific antibody study. No commercial anti-Met617-ox–PIK3C3 Ab found.

Detection: Site ID/quantitation: LC-MS/MS redox proteomics. Pan-MetO Abs can screen bulk Met oxidation but do not specifically report Met617.

Prioritizes kinase-/function-annotated sites (SIGNOR, UniProt, key papers) plus selected acetylation, Ub, SUMO, and oxidation from dbPTM. Where a Detection row is shown for non-phospho sites, literature typically uses pan-PTM antibodies + IP / MS / mutants—commercial site-specific Abs are rare. Many MS high-throughput phospho sites (e.g. Ser25, Ser448/455) are omitted here—see dbPTM / PhosphoSitePlus for the full catalog; verify species numbering before epitope mapping.

Bypass & related pathways

Models & genetics note

Overexpression vs endogenous PIK3C3 can differ in dosage, splicing, and compartmentation—in organoids/PDX, record passage, matrix, and drug history.

Quick search presets

PIK3C3PIK3C3 antibodyPI3K inhibitormTOR inhibitor

PIK3C3-related antibodies (keyword-biased)

Adds PIK3C3 keyword bias atop the PI3K/Akt/mTOR antibody pool—if sparse, use presets above or global search.

Neighboring targets (same hub)

VPS15NRBF2BECN1ATG14UVRAGRUBCNRUBCNLSH3GLB1

External databases & resources

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: 2026-09-04

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.

PI3K/Akt/mTOR·MAPK/ERK·Receptor tyrosine kinase·Metabolism