Study reveals how cells recycle zinc during deficiency through mitochondrial degradation pathway
Researchers have discovered that cells recycle zinc during deficiency by importing the zinc-storing protein metallothionein into mitochondria, where it is degraded by a protease called LONP1 to release zinc locally. This process occurs in two phases: rapid metallothionein breakdown followed by autophagy-dependent degradation of other zinc-binding proteins. The findings reframe mitochondria as active nutrient-recycling centers and could inform understanding of diseases linked to zinc deficiency or mitochondrial dysfunction.
A new preprint study published on bioRxiv reveals a previously unknown mechanism by which cells manage zinc homeostasis under conditions of zinc limitation. Zinc is an essential cofactor for approximately 10% of all proteins, supporting functions across the nucleus, endoplasmic reticulum, and mitochondria. The researchers identified a biphasic cellular response to zinc starvation: first, the zinc-storing protein metallothionein is rapidly imported into mitochondria and degraded by the mitochondrial protease LONP1, releasing zinc locally; second, other zinc-binding proteins are degraded through autophagy. Zinc starvation was found to cause severe mitochondrial dysfunction, and metallothionein degradation appears to alleviate this stress by supplying zinc directly where it is needed. This non-canonical degradation pathway challenges the conventional view of mitochondria as primarily energy-producing organelles, establishing them instead as active hubs for nutrient sensing and recycling. The study adds important mechanistic detail to the broader field of micronutrient homeostasis, though as a preprint it has not yet undergone formal peer review.
What's missing
As a preprint, this study has not yet undergone formal peer review. Key open questions include whether this mitochondrial zinc-recycling mechanism operates similarly across different cell types and organisms, how LONP1 selectively recognizes metallothionein for import and degradation, and whether dysregulation of this pathway contributes to specific human diseases. The study's scope appears limited to cellular models, and in vivo validation in whole organisms has not been reported.
What different sources said
- bioRxivCenter
Mitochondrial degradation of metallothionein enables local zinc mobilization during zinc limitation
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