Regulation of peroxisome dynamics

Abstract

Peroxisomes are single-membraned organelles ubiquitous to eukaryotic cells that house metabolic reactions that generate and destroy harmful oxidative intermediates. They are dynamic structures whose morphology, abundance, composition, and function depend on the cell type and environment. Perhaps due to the potentially damaging and protective metabolic roles of peroxisomes and their dynamic presence in the cell, peroxisome biogenesis is emerging as a process that involves complex underlying mechanisms of regulated formation and maintenance. There are roughly 30 known peroxins, proteins involved in peroxisome biogenesis, many of which have been conserved from yeast to mammals. This review focuses on the biogenesis of peroxisomes with an emphasis on the regulation of peroxisome formation and the import of peroxisomal matrix proteins in the model organism Saccharomyces cerevisiae.

Figure 1

Peroxisomes arise de novo only in the absence of preexisting peroxisomes. WT (left panels) and INP2Δ cells (right panels) constitutively expressing HcRed-PTS1 (under control of the TPI1 promoter) were pulse labeled with GFP-PTS1 (under control of the GAL1 promoter) and then allowed to form a colony over 6–8 h on glucose containing medium. All peroxisomes in the colony of wild-type cells were labeled with both markers indicating that all peroxisome in the colony had derived by fission of the peroxisomes present in the parent cells. However, in the INP2Δ colony of cells defective in peroxisome inheritance, many peroxisomes contained only HcRed-PTS1, indicating de novo generation of peroxisomes in the absence of preexisting peroxisomes [29] (reproduced with permission).

Figure 2

Single particle analysis of purified recombinant H. polymorpha Pex5p. (A) Average projection map of Pex5p in the closed conformation. (B–D) Pex5p in the open conformation in the presence of Pex20p. Some complexes appear to have no Pex20p association as in panel B; but 75% of the Pex5p tetramers are associated with between 1–3 globular mass of about 80 Ǻ shown in panels C and D. The bar equals 10 nm. [59] (reproduced with permission)