Peroxisomal Membrane Protein Import Does Not Require Pex17p

Courtney C Harper,Sarah T South,J Michael Mccaffery,Stephen J Gould

doi:10.1074/jbc.m111728200

Abstract

Of the approximately 20 proteins required for peroxisome biogenesis, only four have been implicated in the process of peroxisomal membrane protein (PMP) import: Pex3p, Pex16p, Pex17p, and Pex19p. To improve our understanding of the role that Pex17p plays in PMP import, we examined the behavior of PMPs in a Pichia pastoris pex17 mutant. Relative to wild-type cells, pex17 cells appeared to have a mild reduction in PMP stability and slightly aberrant PMP behavior in subcellular fractionation experiments. However, we also found that the behavior of PMPs in the pex17 mutant was indistinguishable from PMP behavior in a pex5 mutant, which has no defect in PMP import, and was far different from PMP behavior in a pex3 mutant, which has a bona fide defect in PMP import. Furthermore, we found that a pex14 mutant, which has no defect in PMP import, lacks detectable levels of Pex17p. Based on these and other results, we propose that Pex17p acts primarily in the matrix protein import pathway and does not play an important role in PMP import.

Highlights

Eukaryotic cells contain specialized organelles that enhance their metabolic efficiency
Import result in rapid turnover and low steady state levels of most peroxisomal membrane protein (PMP) [8, 15,16,17, 23, 32]. To determine whether this was true for cells lacking Pex17p, we examined the abundance of three integral PMPs in a P. pastoris pex17⌬ strain: Pex3p [33], Pex10p [30], and Pex12p [31]
The first consideration in trying to determine whether a particular peroxin participates in matrix protein import or PMP import is to determine whether the peroxin is essential for PMP import

Summary

Introduction

Eukaryotic cells contain specialized organelles that enhance their metabolic efficiency. The pex17⌬ mutant was thought to import PMPs less efficiently than wild-type cells Based on these results, Snyder et al [26] and Subramani et al [14] have proposed that Pex17p plays a specific role in PMP import, with the matrix protein import defect of pex17⌬ cells resulting indirectly from this defect in PMP biogenesis. Pex17⌬ cells show a phenotype that is very different from that of pex3⌬ cells, which have a clear role in PMP biogenesis Based on these and other results, we conclude that P. pastoris Pex17p plays an important role in peroxisomal matrix protein import but has no detectable role in PMP import or any other aspect of PMP biogenesis

Methods

Results

Conclusion