Cuproptosis: Copper-Dependent Cell Death

Why Cuproptosis?

• A recently defined form of regulated cell death, driven by direct binding
  of copper to lipoylated mitochondrial TCA-cycle proteins.
• Mechanistically distinct from apoptosis, necroptosis, ferroptosis, and pyroptosis.
• Sensitivity tracks with reliance on mitochondrial respiration — making it a
  fast-growing focus in cancer therapy and copper-overload disease.
• Named and defined only in 2022 (Tsvetkov et al.), so literature and the
  corresponding GO annotations are still young and incomplete.
• Parallels the existing Ferroptosis project as a metal-dependent
  regulated-cell-death pathway.

Key Biology / Mechanism

1. Copper enters the cell and reaches mitochondria.
2. The ferredoxin FDX1 reduces Cu²⁺ → Cu⁺.
3. Cu⁺ binds lipoylated DLAT (E2 of the pyruvate dehydrogenase complex).
4. DLAT undergoes disulfide-bond–dependent oligomerization / aggregation —
   a hallmark of cuproptosis.
5. Fe–S cluster proteins are destabilized.
6. The resulting proteotoxic stress kills the cell.

FDX1 is also required for protein lipoylation — the very modification that
serves as the "bait" copper attacks.

The Approach: AI Gene Review

• Systematically review existing GO annotations for each pathway gene using
  strict GO guidelines.
• Synthesize with literature evidence and bioinformatic inference.
• Distinguish core functions from over-annotation (e.g. generic "cell death"
  terms with only indirect support).
• Scope ontology gaps for this new modality.
• Status: SCOPING — gene folders still need setup
  (just fetch-gene human <GENE>).

Pathway Architecture

• Copper delivery & homeostasis — set the threshold for cuproptosis
  (SLC31A1, ATP7A, ATP7B, ATOX1).
• Copper reduction (the trigger) — FDX1 reduces Cu²⁺ → Cu⁺.
• Protein lipoylation machinery — installs the lipoyl "bait"
  (LIAS, LIPT1, LIPT2, DLD).
• Lipoylated targets (death effectors) — copper-attacked
  (DLAT, PDHA1, PDHB, GCSH).
• Regulators & specificity controls — set sensitivity
  (MTF1, GLS, CDKN2A, FDX2).

Priority 1: Core Execution Machinery

~7 genes — the direct executioners of cuproptosis.

Priority 2: Copper Handling & Regulation

~6 genes — they set the copper threshold and tune sensitivity.

Priority 3: Supporting / Specificity Genes

~4 genes. Note: FDX2 does NOT substitute for FDX1 in cuproptosis — a useful
specificity control.

Key Recent Discoveries

1. FDX1 = target of the copper ionophore elesclomol
   — Tsvetkov et al., Nat Chem Biol 2019 (PMID:31133756). Established the
   FDX1–copper axis in regulated cell death.
2. Definition of cuproptosis
   — Tsvetkov et al., Science 2022 (PMID:35298263; erratum PMID:36356160).
   Genome-wide CRISPR screens identified FDX1 and the lipoylation pathway;
   showed copper binds lipoylated DLAT → aggregation + Fe–S cluster loss.
3. Mechanistic / therapeutic syntheses
   — Tang, Chen & Kang, Mol Cell 2022 (PMID:35594843). Placed cuproptosis
   among regulated-cell-death pathways with cancer-therapy implications.

Disease & Therapeutic Relevance

• Copper-handling disorders frame the homeostatic thresholds:
  • Wilson disease (ATP7B loss → copper overload)
  • Menkes disease (ATP7A loss → copper deficiency)
• Cancer therapy:
  • Copper ionophores (elesclomol, disulfiram–Cu) selectively kill cells
    dependent on mitochondrial respiration / high lipoylation.
  • Copper chelators (e.g. tetrathiomolybdate) block cuproptosis.
• Biomarker biology: FDX1 and lipoylation status are emerging predictors of
  cuproptosis susceptibility across tumor types.

Challenges: New Modality, GO Term Gaps

• Is there (or should there be) a GO biological-process term for cuproptosis,
  analogous to GO:0097707 ferroptosis? Scope the ontology gap.
• Are FDX1's two roles (Cu²⁺ reduction vs. promoting lipoylation) captured
  by distinct, appropriately specific MF/BP terms — or over-/under-annotated?
• DLAT: distinguish its canonical acetyltransferase MF from its
  cuproptosis-effector behavior (copper-induced aggregation) — the latter is a
  process role, not a new MF.
• Watch for over-annotation of every lipoylation/TCA gene with a generic
  "cell death" process term where experimental support is indirect.

Conclusions & Future Directions

• Cuproptosis: copper-dependent regulated cell death executed via lipoylated
  TCA-cycle proteins and Fe–S cluster loss — a young, fast-moving field.
• Curation target: ~17 genes across 3 priority tiers (core execution,
  copper handling, specificity controls).
• Status: SCOPING. Next steps:
  • [ ] Gene folder setup (just fetch-gene human <GENE>)
  • [ ] Priority 1 genes (0/7), Priority 2 (0/6), Priority 3 (0/4)
  • [ ] Pathway summary + ontology-gap assessment
• Parallels the Ferroptosis project as a metal-dependent cell-death pathway.