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PEX12 interacts with PEX5 and PEX10 and acts downstream of receptor docking in peroxisomal matrix protein import
C C Chang1, D S Warren, K A Sacksteder
1The Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Insights
Peroxisomal import protein PEX12
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Peroxisomal matrix protein import is crucial for cellular function.
- PEX12, an integral peroxisomal membrane protein, is essential for this process.
- Mutations in PEX12 cause Zellweger syndrome, a severe neurological disorder.
Purpose of the Study:
- To investigate the role of the PEX12 zinc ring domain in peroxisomal protein import.
- To identify PEX12 interacting partners and their functional significance.
- To elucidate the mechanism of PEX12 in the context of Zellweger syndrome.
Main Methods:
- Two-hybrid studies
- Blot overlay assays
- Coimmunoprecipitation experiments
- Patient mutation analysis
- Overexpression studies
Main Results:
- The PEX12 zinc-binding domain interacts with PEX5 (PTS1 receptor) and PEX10.
- A patient mutation (S320F) in the PEX12 zinc-binding domain impairs binding to PEX5 and PEX10.
- PEX5 and PEX10 binding to PEX12 is biologically relevant, as indicated by suppression studies.
- PEX12 and PEX10 are not involved in the docking of PEX5 to the peroxisome.
Conclusions:
- PEX12, PEX5, and PEX10 form a functional complex.
- PEX12's zinc-binding domain is critical for its interaction with PEX5 and PEX10.
- PEX12 and PEX10 mediate peroxisomal matrix protein import downstream of receptor docking.
- Understanding these interactions provides insights into Zellweger syndrome pathogenesis.
Abstract:
Peroxisomal matrix protein import requires PEX12, an integral peroxisomal membrane protein with a zinc ring domain at its carboxy terminus. Mutations in human PEX12 result in Zellweger syndrome, a lethal neurological disorder, and implicate the zinc ring domain in PEX12 function. Using two-hybrid studies, blot overlay assays, and coimmunoprecipitation experiments, we observed that the zinc-binding domain of PEX12 binds both PEX5, the PTS1 receptor, and PEX10, another integral peroxisomal membrane protein required for peroxisomal matrix protein import. Furthermore, we identified a patient with a missense mutation in the PEX12 zinc-binding domain, S320F, and observed that this mutation reduces the binding of PEX12 to PEX5 and PEX10. Overexpression of either PEX5 or PEX10 can suppress this PEX12 mutation, providing genetic evidence that these interactions are biologically relevant. PEX5 is a predominantly cytoplasmic protein and previous PEX5-binding proteins have been implicated in docking PEX5 to the peroxisome surface. However, we find that loss of PEX12 or PEX10 does not reduce the association of PEX5 with peroxisomes, demonstrating that these peroxins are not required for receptor docking. These and other results lead us to propose that PEX12 and PEX10 play direct roles in peroxisomal matrix protein import downstream of the receptor docking event.