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Identification and characterization of the human orthologue of yeast Pex14p
G K Will1, M Soukupova, X Hong
1Institut für Physiologische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany.
Insights
Researchers identified human Pex14p (HsPex14p), a key protein in peroxisomal import. HsPex14p interacts with PTS1 receptors, crucial for peroxisome biogenesis and potentially linked to human disorders.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Peroxisomal protein import is essential for cellular function.
- Pex14p in yeast is a convergence point for peroxisomal targeting signals (PTS1 and PTS2).
- Conservation of peroxisomal import pathways between yeast and humans is not fully understood.
Purpose of the Study:
- To identify and characterize the human homolog of yeast Pex14p (HsPex14p).
- To investigate the role of HsPex14p in mammalian peroxisomal protein import.
- To assess HsPex14p as a potential candidate gene for human peroxisome biogenesis disorders.
Main Methods:
- Identification and characterization of HsPex14p.
- Analysis of HsPex14p localization and function using overexpression studies.
- Biochemical assays to study protein-protein interactions (e.g., with PTS1 receptor).
Main Results:
- HsPex14p is a peroxisomal membrane protein with its C-terminus exposed to the cytosol.
- HsPex14p overexpression causes peroxisomal abnormalities and catalase mislocalization.
- HsPex14p directly binds the PTS1 receptor, indicating a role in PTS1-mediated import.
- HsPex14p does not homo-oligomerize or interact with PTS2 receptor or HsPex13p, unlike its yeast counterpart.
Conclusions:
- HsPex14p functions as a membrane receptor for PTS1 import in humans.
- Differences in HsPex14p interactions compared to yeast Pex14p suggest species-specific variations in peroxisomal import.
- HsPEX14 is a strong candidate gene for causing human peroxisome biogenesis disorders.
Abstract:
Pex14p is a central component of the peroxisomal protein import machinery, which has been suggested to provide the point of convergence for PTS1- and PTS2-dependent protein import in yeast cells. Here we describe the identification of a human peroxisome-associated protein (HsPex14p) which shows significant similarity to the yeast Pex14p. HsPex14p is a carbonate-resistant peroxisomal membrane protein with its C terminus exposed to the cytosol. The N terminus of the protein is not accessible to exogenously added antibodies or protease and thus might protrude into the peroxisomal lumen. HsPex14p overexpression leads to the decoration of tubular structures and mislocalization of peroxisomal catalase to the cytosol. HsPex14p binds the cytosolic receptor for the peroxisomal targeting signal 1 (PTS1), a result consistent with a function as a membrane receptor in peroxisomal protein import. Homo-oligomerization of HsPex14p or interaction of the protein with the PTS2-receptor or HsPex13p was not observed. This distinguishes the human Pex14p from its counterpart in yeast cells and thus supports recent data suggesting that not all aspects of peroxisomal protein import are conserved between yeasts and humans. The role of HsPex14p in mammalian peroxisome biogenesis makes HsPEX14 a candidate PBD gene for being responsible for an unrecognized complementation group of human peroxisome biogenesis disorders.