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Human adrenoleukodystrophy protein and related peroxisomal ABC transporters interact with the peroxisomal assembly
C J Gloeckner1, P U Mayerhofer, P Landgraf
1GSF-National Research Center for Environment and Health, Institute of Mammalian Genetics, Ingolstaedter Landstrasse 1, Neuherberg, 85764, Germany.
Abstract:
Four ABC half transporters (ALDP, ALDRP, PMP70, and PMP69) have been identified in the mammalian peroxisomal membrane but no function has been unambiguously assigned to any of them. To date X-linked adrenoleukodystrophy (X-ALD) is the only human disease known to result from a defect of one of these ABC transporters, ALDP. Using the yeast two-hybrid system and in vitro GST pull-down assays, we identified the peroxin PEX19p as a novel interactor of ALDP, ALDRP, and PMP70. The cytosolic farnesylated protein PEX19p was previously shown to be involved in an early step of the peroxisomal biogenesis. The PEX19p interaction occurs in an internal N-terminal region of ALDP which we verified to be important for proper peroxisomal targeting of this protein. Farnesylated wild-type PEX19p and a farnesylation-deficient mutant PEX19p did not differ in their ability to bind to ALDP. Our data provide evidence that PEX19p is a cytosolic acceptor protein for the peroxisomal ABC transporters ALDP, PMP70, and ALDRP and might be involved in the intracellular sorting and trafficking of these proteins to the peroxisomal membrane.
Insights
The peroxin PEX19p interacts with peroxisomal ABC transporters ALDP, ALDRP, and PMP70. This interaction is crucial for the sorting and trafficking of these transporters to the peroxisomal membrane.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Mammalian peroxisomal membranes contain four identified ABC half transporters: ALDP, ALDRP, PMP70, and PMP69.
- X-linked adrenoleukodystrophy (X-ALD) is the sole human disease linked to a defect in the ABC transporter ALDP.
- The peroxin PEX19p is a cytosolic, farnesylated protein previously implicated in peroxisomal biogenesis.
Purpose of the Study:
- To identify novel interactors of peroxisomal ABC transporters.
- To elucidate the role of PEX19p in the function and localization of peroxisomal ABC transporters.
Main Methods:
- Yeast two-hybrid system screening.
- In vitro GST pull-down assays.
- Analysis of protein-protein interactions and peroxisomal targeting.
Main Results:
- PEX19p was identified as a novel interactor of ALDP, ALDRP, and PMP70.
- The interaction site on ALDP was mapped to an N-terminal region critical for peroxisomal targeting.
- Farnesylation status of PEX19p did not affect its binding affinity to ALDP.
Conclusions:
- PEX19p acts as a cytosolic acceptor protein for peroxisomal ABC transporters ALDP, PMP70, and ALDRP.
- PEX19p likely plays a role in the intracellular sorting and trafficking of these transporters to the peroxisomal membrane.