Intramitochondrial seeding and sorting of protein aggregates

Introduction

Quality control processes maintain mitochondrial health, enabling cellular functions such as bioenergetics, metabolism, Ca2+ signaling, and cell death regulation. Mitochondrial proteases, unfolded protein response, asymmetric fission, vesicle shedding, and mitophagy all contribute to organelle quality. However, the specific triggers for these processes remain unclear. While unfolded protein accumulation appears to be a common trigger, the mechanism by which it initiates diverse responses remains uncertain.

Research Objectives

To investigate this question, we developed advanced tools for real-time imaging of protein aggregation in mitochondrial subcompartments. Aggregates in the matrix and intermembrane space induce mitochondrial fission and elicit distinct functional responses based on their location.

Findings

Live imaging revealed that intermembrane space aggregates initially seed in the mitochondrial midzone and then sort through transient side-by-side fusion with neighboring mitochondria. In the matrix, aggregates seed at one pole and are selectively sorted to daughter mitochondria through asymmetric fission. Our preliminary experiments unveiled an early seeding and sorting process of protein aggregates according to their intramitochondrial location.

Project Goals

In the INTEGRATE project, we aim to comprehensively understand the underlying principles and consequences of this process. By combining:

1. Advanced imaging techniques
2. Omics analysis
3. Biochemistry
4. Functional assays
5. Unbiased screenings

we will decipher the rules governing aggregate formation, seeding, sorting, cellular fate, and response in various mitochondrial subcompartments.

Implications

INTEGRATE seeks to establish the occurrence and downstream responses of this newly discovered early phase of mitochondrial quality control. Clarifying this fundamental mechanism will provide insights into mitochondrial and cell biology, with significant implications for pathological conditions and aging, where mitochondrial quality control is compromised.