Peroxisome biogenesis initiated by protein phase separation

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Peroxisomes are vital organelles involved in metabolic processes like β-oxidation.
• Dysfunction of peroxisomes and their protein import machinery leads to various diseases.
• The peroxisomal protein import mechanism is unique, transporting large, folded protein complexes.

Purpose of the Study:

• To investigate the mechanism of protein transport into peroxisomes.
• To elucidate the role of Pex13 and Pex5 in peroxisomal protein import.
• To explore the involvement of liquid-liquid phase separation (LLPS) in this process.

Main Methods:

• Studied the interaction of Pex13 with Pex5-cargo using liquid-liquid phase separation (LLPS) assays.
• Analyzed intrinsically disordered regions (IDRs) of Pex13 and Pex5.
• Utilized imaging fluorescence cross-correlation spectroscopy (FCS) to observe protein dynamics on the peroxisome membrane.

Main Results:

• Pex13 undergoes LLPS with Pex5-cargo, mediated by aromatic residues in their intrinsically disordered regions.
• Cargo import correlates with transient Pex13 and Pex14 foci formation on the peroxisome membrane.
• Pex13 and Pex14 form distinct foci, suggesting sequential channel formation.

Conclusions:

• LLPS of Pex5-cargo with Pex13 and Pex14 forms transient protein transport channels.
• This mechanism provides new insights into peroxisomal protein import and potential disease pathways.
• The findings propose a novel model for peroxisomal protein translocation.