Abstract
Proteins are subject to continuous quality control for optimal proteostasis. The knowledge of peroxisome quality control systems is still in its infancy. Here we show that peroxisomes contain a member of the Lon family of proteases (Pln). We show that Pln is a heptameric protein and acts as an ATP-fueled protease and chaperone. Hence, Pln is the first chaperone identified in fungal peroxisomes. In cells of a PLN deletion strain peroxisomes contain protein aggregates, a major component of which is catalase-peroxidase. We show that this enzyme is sensitive to oxidative damage. The oxidatively damaged, but not the native protein, is a substrate of the Pln protease. Cells of the pln strain contain enhanced levels of catalase-peroxidase protein but reduced catalase-peroxidase enzyme activities. Together with the observation that Pln has chaperone activity in vitro, our data suggest that catalase-peroxidase aggregates accumulate in peroxisomes of pln cells due to the combined absence of Pln protease and chaperone activities.
Highlights
A putative Lon protease has been identified in peroxisomes of various species (Pln)
As peroxisomes are oxidative organelles, we studied whether oxidative stress may cause catalase-peroxidase enzyme inactivation or protein aggregation
In this work we provide evidence that peroxisomes of the fungus P. chrysogenum contain an isoform of the Lon protease, termed Pln, a member of the AAA protein family, that displays a dual function as ATP-stimulated protease in conjunction with a role as molecular chaperone
Summary
A putative Lon protease has been identified in peroxisomes of various species (Pln). Results: Pln is an ATP-dependent protease that digests unfolded substrates e.g. oxidatively damaged catalase-peroxidase, and displays chaperone-like activity, circumventing accumulation of protein aggregates in peroxisomes that compromise organelle function. We show that peroxisomes contain a member of the Lon family of proteases (Pln). Pln is the first chaperone identified in fungal peroxisomes. In cells of a PLN deletion strain peroxisomes contain protein aggregates, a major component of which is catalase-peroxidase. We show that this enzyme is sensitive to oxidative damage. Cells of the pln strain contain enhanced levels of catalase-peroxidase protein but reduced catalase-peroxidase enzyme activities. Together with the observation that Pln has chaperone activity in vitro, our data suggest that catalase-peroxidase aggregates accumulate in peroxisomes of pln cells due to the combined absence of Pln protease and chaperone activities
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