POTEE

POTEE is a cancer-testis antigen that functions as a pro-tumorigenic signaling scaffold, promoting cell proliferation, migration, invasion, and metastasis across multiple cancer types by activating Rac1/Cdc42 small GTPases and downstream oncogenic pathways. POTEE serves as an effector of SUMOylated Rac1, recruiting the guanine nucleotide exchange factor TRIO to drive invadopodium formation in breast cancer (PMID:38098337), and independently activates Rac1/Cdc42 to promote epithelial-mesenchymal transition in colorectal carcinoma (PMID:32142855). POTEE also engages the mTORC2 complex through interactions with mTOR and RICTOR in macrophages, activating AKT and PKC-α signaling (PMID:30420269, PMID:30391463), and stimulates PI3K/Akt/GSK-3β/β-catenin and SPHK1/NF-κB/p65 axes to drive proliferation in pancreatic and colorectal cancers (PMID:32589786, PMID:31723122). POTEE protein stability is regulated by TRIM33-mediated ubiquitination, which is facilitated by direct binding of the lncRNA LINC00667, and POTEE degradation reduces mitochondrial OXPHOS complex expression (PMID:40834976).

1. 2018 Medium

   The discovery that POTEE physically interacts with mTORC2 components (mTOR, RICTOR) and that its knockdown impairs macrophage survival established POTEE as a signaling-active protein rather than merely a cancer-testis marker, linking it to a defined kinase signaling complex.

   Evidence Co-immunoprecipitation and siRNA knockdown in macrophage and tumor-associated macrophage cell models

   PMID:30391463 PMID:30420269

   Open questions at the time

   • No direct kinase assay showing POTEE stimulates mTORC2 catalytic activity
   • Mechanism by which POTEE promotes mTORC2 assembly or activation is undefined
   • Findings limited to macrophage lineage; generalizability uncertain
2. 2019 Medium

   Identification of the POTEE/SPHK1/p65 axis in colorectal cancer demonstrated that POTEE acts upstream of NF-κB signaling by increasing SPHK1 protein levels, providing the first cancer-intrinsic signaling pathway downstream of POTEE.

   Evidence Microarray, western blotting, overexpression/knockdown in CRC cells, and xenograft tumor model

   PMID:31723122

   Open questions at the time

   • No direct biochemical mechanism for how POTEE upregulates SPHK1
   • Pathway ordering inferred from correlative protein level changes
   • Single lab finding without independent replication
3. 2020 Medium

   Demonstration that POTEE activates Rac1 and Cdc42 GTPases to drive EMT, migration, and invasion established small GTPase activation as a core effector mechanism of POTEE in colorectal cancer, while a parallel study linked POTEE to PI3K/Akt/GSK-3β/β-catenin in pancreatic cancer proliferation.

   Evidence GTPase activation pull-down assays, siRNA knockdown/overexpression, in vivo metastasis model (CRC); siRNA knockdown with GSK-3β inhibitor epistasis and western blotting (pancreatic cancer)

   PMID:32142855 PMID:32589786

   Open questions at the time

   • PI3K/Akt pathway activation inferred from protein level changes without direct biochemical reconstitution (Low confidence for pancreatic cancer study)
   • Whether Rac1/Cdc42 and PI3K/Akt represent parallel or converging mechanisms is unknown
   • No GEF or GAP identified mediating POTEE-dependent GTPase activation at this stage
4. 2021 Medium

   Discovery that POTEE is required for NMT1-mediated N-myristoylation of specific substrate proteins expanded POTEE's role beyond signaling scaffold to a co-factor for a lipid modification enzyme, connecting it to protein stability through differential ubiquitination.

   Evidence Click chemistry myristoylation assay, iTRAQ proteomics, conditional NMT1 knockout mouse model, PRM in liver cancer cells

   PMID:34136404

   Open questions at the time

   • Molecular mechanism by which POTEE enables NMT1 activity is not defined
   • Whether POTEE is a direct NMT1 binding partner or acts indirectly is unresolved
   • Relationship of NMT1/myristoylation function to POTEE's GTPase-activating roles is unclear
5. 2023 Medium

   Identification of POTEE as an effector of SUMOylated Rac1 that recruits the GEF TRIO to invadopodia resolved the upstream signal (Rac1-SUMO1) and the direct mechanism (TRIO recruitment) by which POTEE activates Rac1 at sites of invasion, unifying earlier GTPase activation findings with a defined molecular cascade.

   Evidence Co-immunoprecipitation, co-localization, TRIO-GEF recruitment assays, invadopodium formation assays, and in vivo metastasis assays in breast cancer models

   PMID:38098337

   Open questions at the time

   • Structural basis of POTEE-TRIO and POTEE-SUMOylated Rac1 interactions is unknown
   • Whether TRIO recruitment mechanism operates in cancer types beyond breast cancer is untested
   • Single lab; no independent confirmation of the SUMOylated Rac1–POTEE–TRIO cascade
6. 2024 Low

   Finding that MARK1 kinase binds POTEE and negatively regulates its expression identified the first upstream kinase-level negative regulator of POTEE, relevant to sorafenib resistance in hepatocellular carcinoma.

   Evidence Luciferase reporter binding assay, rescue/epistasis experiment with co-overexpression, sorafenib-resistant HCC cell model

   PMID:39534429

   Open questions at the time

   • No direct biochemical mechanism for how MARK1 suppresses POTEE expression (phosphorylation site, degradation, transcriptional effect all undefined)
   • Luciferase reporter binding assay is non-standard for protein-protein interaction validation
   • Single lab, single cancer model
7. 2025 Medium

   Demonstration that the lncRNA LINC00667 directly binds POTEE protein and promotes TRIM33-mediated ubiquitination and proteasomal degradation revealed the first defined post-translational regulatory mechanism controlling POTEE protein levels, and linked POTEE stability to mitochondrial OXPHOS complex expression.

   Evidence CHIRP and RIP assays for RNA-protein interaction, cycloheximide chase and MG132 treatment, OXPHOS complex western blotting in breast cancer cells

   PMID:40834976

   Open questions at the time

   • TRIM33 ubiquitination sites on POTEE are not mapped
   • How POTEE maintains OXPHOS complex expression is mechanistically undefined
   • Whether LINC00667/TRIM33 axis regulates POTEE in non-breast tissues is unknown

• The structural basis of POTEE's multi-pathway scaffolding activity — how a single protein engages TRIO, mTORC2 components, and NMT1, and whether these represent mutually exclusive or concurrent interactions — remains undefined, and no crystal or cryo-EM structure of POTEE or its complexes has been reported.
• No structural model of POTEE or any of its complexes exists
• Domain-interaction mapping for individual binding partners is incomplete
• All pathway studies originate from single labs without independent replication