Newly imported proteins in mitochondria are particularly sensitive to aggregation

Area of Science:

• Mitochondrial Biology
• Cellular Stress Response
• Protein Homeostasis

Background:

• Protein quality control (PQC) maintains proteome function, with mitochondrial PQC crucial for cellular fitness.
• Protein aggregation signals PQC decline, linked to aging and disease.
• Mechanisms of mitochondrial PQC, especially aggregate handling, remain poorly understood.

Purpose of the Study:

• Investigate how metabolic status impacts mitochondrial aggregate formation and clearance in yeast.
• Identify proteins susceptible to denaturation within mitochondria.
• Elucidate the role of mitochondrial disaggregase Hsp78 in aggregate handling.

Main Methods:

• Utilized confocal and electron microscopy, immunoblotting, and genetic approaches.
• Assessed mitochondrial aggregate handling under heat shock and ethanol stress.
• Employed Hsp78 as a marker for mitochondrial protein aggregates.

Main Results:

• Metabolic state dictates aggregate dynamics: fermentation yields persistent aggregates, while respiration allows efficient clearance.
• Heat or ethanol stress induced aggregates with varying dynamics based on metabolic state.
• Inhibition of cytosolic translation prevented aggregate formation, suggesting newly imported proteins are vulnerable.

Conclusions:

• Cellular metabolic status significantly affects mitochondrial aggregate formation and clearance dynamics.
• Newly imported and unassembled proteins are primarily prone to aggregation.
• Efficient protein biogenesis is vital for maintaining mitochondrial proteome function during metabolic adaptation and stress.