CHPT1

CHPT1 is a Golgi-resident, Mg2+-dependent cholinephosphotransferase that catalyzes the final step of the Kennedy (CDP-choline) pathway, transferring phosphocholine from CDP-choline onto diacylglycerol to produce phosphatidylcholine (PMID:36871755, PMID:37179328, PMID:40435706). Cryo-EM structures of the Xenopus and human enzymes reveal a homodimer in which each protomer folds into 10 transmembrane helices, with the first six forming a cone-shaped, cytosol-facing catalytic enclosure that coordinates CDP-choline and two Mg2+ ions and admits the DAG substrate; an internal pseudo two-fold symmetry between the TM3–6 and TM7–10 halves points to an evolutionary origin by gene duplication (PMID:37179328, PMID:40435706). Structure-guided mutagenesis pinpoints catalytic-domain residues that make CHPT1 strictly PC-specific, distinguishing it from its ER paralog CEPT1, which also synthesizes PE (PMID:40435706, PMID:36871755, PMID:37179328). Although CHPT1 accounts for roughly half of cellular PC synthesis, the Golgi-derived PC it produces is functionally distinct from ER-derived PC: CHPT1 loss does not feed back on CCTα or affect lipid droplet biogenesis, functions reserved for CEPT1 (PMID:36871755). In cancer contexts CHPT1 is a transcriptionally regulated effector of lipid metabolism—directly activated by ERα in breast cancer and by an androgen-receptor super-enhancer in castration-resistant prostate cancer to drive PC synthesis and growth or therapy resistance (PMID:27457520, PMID:32917955)—while in pancreatic cancer CHPT1 acts as a tumor suppressor by recruiting the phosphatase PTPN1 to dephosphorylate STAT3 at Y705, repressing SLC7A11 and promoting ferroptosis (PMID:41337814).

1. 2016 Medium

   Established that CHPT1 is a hormonally regulated metabolic gene by showing ERα directly binds its locus and drives PC synthesis and oncogenic growth, framing CHPT1 as a downstream effector of estrogen signaling rather than a constitutive housekeeping enzyme.

   Evidence Genome-wide ERα ChIP-seq, siRNA/shRNA silencing, metabolic profiling, and zebrafish xenograft in tamoxifen-resistant breast cancer cells

   PMID:27457520

   Open questions at the time

   • Does not resolve the enzymatic mechanism or subcellular site of CHPT1 action
   • Causal link between PC synthesis and the growth/metastasis phenotype is correlative
2. 2019 Low

   Placed Kennedy-pathway choline phospholipid synthesis, including CHPT1-derived species, in the context of autophagosomal membrane biogenesis, raising the question of whether CHPT1 specifically supplies autophagy membranes.

   Evidence 13C-choline MRS tracing, propargylcholine labeling with fluorescence and immunogold colocalization with LC3+ autophagosomes

   PMID:31517566

   Open questions at the time

   • CHPT1-specific functional data not isolated; mechanistic experiments centered on PCYT1A
   • No knockout or perturbation of CHPT1 itself in this context
3. 2020 Medium

   Showed how CHPT1 expression is rewired during therapy resistance, demonstrating that AR relocates to a CHPT1 super-enhancer in enzalutamide-resistant prostate cancer to drive androgen-independent expression and confer drug resistance.

   Evidence H3K27ac and AR ChIP-seq, enhancer RNA–BRD4 RNA pulldown, and CHPT1 overexpression in cell lines and xenograft mice

   PMID:32917955

   Open questions at the time

   • Does not establish whether CHPT1 enzymatic activity (vs. another function) mediates resistance
   • Single-lab functional validation
4. 2023 High

   Defined the core enzymatic identity and compartmental division of labor of CHPT1, establishing it as a Golgi PC-specific cholinephosphotransferase contributing ~half of cellular PC, whose product is functionally distinct from ER-derived PC.

   Evidence CRISPR-Cas9 knockout in U2OS cells with radiolabeled synthesis assays, CCTα regulation readouts, lipid droplet assays, PC liposome rescue, and direct CEPT1 KO comparison

   PMID:36871755

   Open questions at the time

   • Molecular basis of Golgi-versus-ER PC functional specialization not resolved
   • Does not explain why Golgi PC fails to feed back on CCTα
5. 2023 High

   Provided the first near-atomic structural framework for the reaction, revealing a homodimeric 10-TM architecture with a cytosol-facing catalytic enclosure coordinating CDP-choline and two Mg2+ ions, and inferring an entryway for DAG.

   Evidence Cryo-EM structure of Xenopus CHPT1 at ~3.2 Å with structural analysis of substrate coordination

   PMID:37179328

   Open questions at the time

   • DAG binding mode inferred rather than directly visualized
   • Structure is of the Xenopus ortholog, not human
6. 2025 High

   Resolved the structural and residue-level basis of CHPT1 substrate selectivity in the human enzyme, explaining why CHPT1 is PC-specific while CEPT1 is bifunctional for PC and PE.

   Evidence Cryo-EM structure of human CHPT1 at 3.7 Å with structure-guided site-directed mutagenesis, biochemical activity assays, and cross-species sequence alignment

   PMID:40435706

   Open questions at the time

   • Functional consequences of predicted ovipara bifunctionality not tested in vivo
   • Catalytic transition-state mechanism not directly determined
7. 2025 Medium

   Uncovered a non-canonical, context-dependent tumor-suppressive function in which CHPT1 scaffolds PTPN1 to dephosphorylate STAT3 (Y705), repress SLC7A11, and trigger ferroptosis, contrasting with its pro-tumorigenic roles in other cancers.

   Evidence Lentiviral CHPT1 overexpression/knockdown, CHPT1–PTPN1 co-immunoprecipitation, phospho-STAT3 western blot, SLC7A11 transcription assays, PTPN1-knockdown epistasis, and xenograft ferroptosis assays in PDAC

   PMID:41337814

   Open questions at the time

   • Co-IP without reciprocal validation; direct CHPT1–PTPN1 binding interface unmapped
   • Whether catalytic activity or PC product is required for the PTPN1 scaffold function is unresolved
8. 2025 Medium

   Linked CHPT1-driven PC accumulation to chemoresistance in colorectal cancer, proposing that PC enrichment sustains pro-survival signaling and that upstream Kennedy-pathway inhibition can restore sensitivity.

   Evidence CHPT1 overexpression in SW620 cells, lipidomic profiling, edelfosine pharmacological treatment, and drug-sensitivity assays

   PMID:41827872

   Open questions at the time

   • Mechanistic link between PC enrichment and survival signaling is proposed, not directly demonstrated
   • Edelfosine acts broadly on lipid rafts and the Kennedy pathway, not selectively on CHPT1

• It remains unresolved how a single PC-synthesizing enzyme produces opposing oncogenic and tumor-suppressive outcomes across tissues, and whether its scaffolding of PTPN1 depends on catalytic activity or PC product.
• No unifying model reconciling context-dependent pro- and anti-tumor roles
• Catalytic-versus-scaffold dependence of the CHPT1–PTPN1–STAT3 axis untested
• Molecular basis of Golgi PC functional specialization unknown