Mitophagy (PINK1 / Parkin)

What it is

Mitophagy is the selective removal of damaged or excess mitochondria by autophagy. The canonical PINK1/Parkin pathway works as follows:

1. Healthy mitochondria import PINK1 across the inner membrane where it is constitutively degraded.
2. Membrane-potential loss stabilises PINK1 on the outer membrane.
3. PINK1 recruits and activates Parkin (an E3 ubiquitin ligase).
4. Parkin ubiquitinates outer-membrane proteins, marking the organelle for autophagosome capture.

Receptor-mediated mitophagy (BNIP3, NIX, FUNDC1) operates in parallel.

Why it matters in aging

Mitophagy flux declines with age in most tissues. PINK1 and Parkin loss-of-function mutations cause familial Parkinson’s disease, illustrating how mitophagy failure damages neurons over decades.

What activates mitophagy

• Energy stress (AMPK activation).
• Spermidine, urolithin A (best-evidenced supplement for mitophagy).
• Exercise.
• Rapamycin (via general autophagy up-regulation).

Longevity relevance

Mitophagy — the selective autophagy of damaged or superfluous mitochondria — declines with age, contributing to the accumulation of dysfunctional mitochondria that drive mitochondrial dysfunction.

Mechanisms

• PINK1/Parkin pathway: PINK1 accumulates on depolarised mitochondrial outer membrane → recruits Parkin (E3 ubiquitin ligase) → mitochondrial proteins ubiquitinated → autophagy receptors (OPTN, NDP52, p62) recruit LC3+ autophagosomes.
• Receptor-mediated mitophagy: BNIP3, NIX, FUNDC1 receptors bind LC3 directly under stress conditions.
• Ubiquitin-independent mitophagy: newer mechanisms including Bcl2L13 and AMBRA1-mediated pathways.

Aging effects

Reduced mitophagy contributes to accumulation of damaged mitochondria, elevated ROS, altered Ca²⁺ handling, and eventual apoptosis-resistant metabolic dysfunction.

Interventions

• Urolithin A: the best-evidenced mitophagy inducer with human RCT data.
• Rapamycin: indirect mitophagy induction via mTOR inhibition and broader autophagy induction.
• Exercise: induces mitophagy acutely in skeletal muscle.
• NAD+ precursors: mitophagy induction via SIRT1/3 activation.

Related entries

Mitochondrial dysfunction, Disabled macroautophagy, Urolithin A.

Related entries

Disabled macroautophagy, Mitochondrial dysfunction, Urolithin A.