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Updated: May 1, 2026
Monitoring Stub1-Mediated Pexophagy
Published on: May 12, 2023
Pex3p phosphorylation modulates recruitment of myosin V adapters Inp2p and Pex19p to regulate peroxisome partitioning
Barbara Knoblach1, Richard A Rachubinski1
1Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
Abstract:
Yeast cells rely on the actomyosin machinery to mediate organelle motility. The type V myosin motor Myo2p transports organelles along actin cables from the mother cell to the nascent bud. To facilitate this process, organelles have evolved specific adaptor proteins that link them to the cargo-binding domain of Myo2p. Peroxisomes use two such adaptors: Inp2p, the principal determinant of peroxisome inheritance, and the biogenesis factor Pex19p, which has been assigned a secondary role in peroxisome partitioning. Here, we identify a regulatory function for the peroxisome biogenesis factor Pex3p in controlling peroxisome inheritance in the budding yeast, Saccharomyces cerevisiae. Pex3p is an integral membrane protein that contains a cytosol-exposed surface loop subject to phosphorylation. This loop is essential for the recruitment of both Inp2p and Pex19p. Phosphorylation of serine residues within the loop in response to environmental stimuli abolishes Inp2p binding to, and markedly reduces Pex19p association with, Pex3p, thereby reducing the efficiency of peroxisome partitioning between the mother cell and the bud. Deleting the loop in Pex3p completely abolishes peroxisome segregation. By serving as a membrane anchor for the recruitment of both inheritance factors Inp2p and Pex19p, Pex3p exerts a critical level of control over peroxisome partitioning.
Insights
The peroxisome biogenesis factor Pex3p regulates peroxisome inheritance in yeast by controlling adaptor protein recruitment. Phosphorylation of Pex3p
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Yeast cells utilize the actomyosin system for organelle movement.
- Type V myosin Myo2p motors transport organelles, including peroxisomes, along actin filaments.
- Peroxisomes use adaptor proteins like Inp2p and Pex19p to link with Myo2p for inheritance.
Purpose of the Study:
- To investigate the role of the peroxisome biogenesis factor Pex3p in controlling peroxisome inheritance.
- To elucidate the mechanism by which Pex3p regulates peroxisome partitioning.
Main Methods:
- Investigated the interaction between Pex3p, Inp2p, and Pex19p in Saccharomyces cerevisiae.
- Analyzed the effect of Pex3p phosphorylation on adaptor protein recruitment.
- Utilized genetic modifications, including loop deletion in Pex3p, to assess peroxisome segregation.
Main Results:
- Pex3p possesses a cytosol-exposed loop crucial for recruiting Inp2p and Pex19p.
- Phosphorylation of serine residues in the Pex3p loop, triggered by environmental cues, reduces Inp2p and Pex19p binding.
- Deletion of the Pex3p loop completely disrupts peroxisome segregation, highlighting its essential role.
Conclusions:
- Pex3p acts as a critical membrane anchor for peroxisome inheritance factors Inp2p and Pex19p.
- Pex3p's phosphorylation state dynamically regulates peroxisome partitioning efficiency.
- Pex3p exerts essential control over the segregation of peroxisomes between mother and bud cells.
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