Mitophagy
What It Is
Selective autophagy of mitochondria — damaged, depolarized, or high-ROS mitochondria are tagged, engulfed by a double-membrane autophagosome, and delivered to lysosomes for degradation. The cell’s quality control mechanism for the mitochondrial population. Distinct from macro-autophagy (general protein aggregate clearance) and from biogenesis (mitochondrial creation).
Why it matters for longevity: Age-related decline in mitophagy → accumulation of dysfunctional, high-ROS mitochondria → chronic oxidative stress, cellular senescence, SASP, and metabolic dysfunction. Restoring mitophagy is one of the most validated anti-aging interventions.
PINK1/Parkin Pathway (Canonical)
- Mitochondrial damage → loss of membrane potential (Δψm)
- PINK1 fails to import into mitochondria → accumulates on outer mitochondrial membrane (OMM)
- PINK1 undergoes auto-phosphorylation → phosphorylates OMM proteins and Parkin
- Parkin E3 ubiquitin ligase recruited → ubiquitinates OMM proteins
- Ubiquitin tags → recognized by autophagy receptors (p62/SQSTM1, NDP52, OPTN) → LC3 docking
- Double-membrane autophagosome wraps around the mitochondrion
- Lysosomal fusion → degradation and recycling
Key readout signals: PINK1 accumulation on OMM, Parkin translocation from cytosol to mitochondria, LC3 puncta colocalization with mitochondria, mtDNA copy number reduction during active mitophagy.
Pharmacological Inducerscers
Urolithin A — Direct PINK1/Parkin Activation
UA facilitates PINK1 activation → recruits Parkin. The cleanest pharmacological entry point into the canonical pathway. Dose: 500–1000 mg/day. See Urolithin A.
Rapamycin — mTORC1 Inhibition → ULK1 Release
mTORC1 phosphorylates and inhibits ULK1 (autophagy initiation complex). Rapamycin → mTORC1 inhibition → ULK1 released → initiates autophagosome formation including mitophagic cargo. Indirect entry point — activates general macro-autophagy of which mitophagy is a subset. Dose: 5–10 mg once weekly. See Rapamycin.
Contrast: Rapamycin = broad autophagic clearance; UA = targeted mitochondrial clearance. Both are mitophagy inducers but via different mechanisms. Complementary in a stack.
Spermidine — AMPK/SIRT1 Axis
Spermidine induces mitophagy via AMPK activation and SIRT1 deacetylation of autophagy proteins. Milder than rapamycin or UA. See Exercise Mimetics for broader context.
SLU-PP-332 — Biogenesis (Opposite Pole)
ERR pan-agonist drives massive mitochondrial biogenesis (PGC-1α). Not a mitophagy inducer — drives the opposite pole. The complete mitochondrial lifecycle: Rapamycin or Urolithin A clears old/damaged mitochondria; SLU-PP-332 populates the cleared space with fresh, efficient mitochondria. See SLU-PP-332.
Relationship to Broader Autophagy
| Pathway | Scope | Primary Trigger | Key Compound |
|---|---|---|---|
| Macro-autophagy | General: proteins, organelles, aggregates | mTOR inhibition, AMPK activation | Rapamycin |
| Mitophagy | Mitochondria only (selective) | PINK1/Parkin, cardiolipin exposure | Urolithin A |
| Ribophagy | Ribosomes only | mTOR inhibition | Rapamycin |
| Proteophagy | Protein aggregates only | p62/SQSTM1 | Spermidine |
| Glyophagy | Glycogen only | AMPK activation | Exercise |
Connection to NAD+ and Sirtuins
Mitophagy and NAD+ are deeply linked:
- Damaged mitochondria generate excess ROS → activate PARP → NAD+ depletion
- NMN replenishes the pool that mitophagy-consumed mitochondria were draining
- PCC1 clears senescent cells → eliminates the M1 macrophage source of CD38 (NAD+-destroying enzyme) → NAD+ stops being wasted → NMN stacks land efficiently
- Rapamycin shifts NAD+/NADH toward oxidized ratio (favorable for SIRT1); NMN provides the substrate. Combined = optimal SIRT1 environment
Biometrics / Wearable Signature
- Active mitophagy: transient increase in AMP/ATP ratio → AMPK activation → ↑ fat oxidation
- Post-mitophagy: improved mitochondrial efficiency → lower resting HR, improved HRV (mitochondrial health underpins autonomic function)
- Urolithin A 1000 mg: measurable VO2max improvement (+10.2%) and 6-min walk distance (+33.4 m) in untrained adults without exercise
- Inflammaging reduction (↓ IL-6, TNF-α) from mitophagic clearance of SASP-driving mitochondria
Links
- Urolithin A — primary pharmacological mitophagy inducer (PINK1/Parkin)
- Rapamycin — broad autophagic mitophagy via mTORC1/ULK1
- SLU-PP-332 — biogenesis counterpart (opposite pole of the mitochondrial lifecycle)
- NMN NAD+ — NAD+ replenishment; mitophagy搭档
- PCC1 — senolytic; eliminates the source of mitophagy-inducing stress
- Exercise Mimetics — overlaps with AMPK/PGC-1α axis
- Peptides MOC — peptide/compound index