Pex11mediates peroxisomal proliferation by promoting deformation of the lipid membrane.

Yumi Yoshida,Masanori Honsho,Akinori Itoyama,Hajime Niwa,Yukio Fujiki

doi:10.1242/bio.201410801

Abstract

Pex11p family proteins are key players in peroxisomal fission, but their molecular mechanisms remains mostly unknown. In the present study, overexpression of Pex11pβ caused substantial vesiculation of peroxisomes in mammalian cells. This vesicle formation was dependent on dynamin-like protein 1 (DLP1) and mitochondrial fission factor (Mff), as knockdown of these proteins diminished peroxisomal fission after Pex11pβ overexpression. The fission-deficient peroxisomes exhibited an elongated morphology, and peroxisomal marker proteins, such as Pex14p or matrix proteins harboring peroxisomal targeting signal 1, were discernible in a segmented staining pattern, like beads on a string. Endogenous Pex11pβ was also distributed a striped pattern, but which was not coincide with Pex14p and PTS1 matrix proteins. Altered morphology of the lipid membrane was observed when recombinant Pex11p proteins were introduced into proteo-liposomes. Constriction of proteo-liposomes was observed under confocal microscopy and electron microscopy, and the reconstituted Pex11pβ protein localized to the membrane constriction site. Introducing point mutations into the N-terminal amphiphathic helix of Pex11pβ strongly reduced peroxisomal fission, and decreased the oligomer formation. These results suggest that Pex11p contributes to the morphogenesis of the peroxisomal membrane, which is required for subsequent fission by DLP1.

Highlights

Peroxisomes are single membrane-bound organelles that are involved in long-chain fatty acid oxidation, plasmalogen synthesis, and ROS elimination (van den Bosch et al, 1992; Wanders and Waterham, 2006)
At an early stage of peroxisomal fission, peroxisomes were extended, and Pex11pb-enriched membrane subregions were generated (Fig. 1Aa,b, arrowheads). These subregions were pinched off to form small vesicles in which Pex11pb was concentrated (Fig. 1Ac). This vesicle formation depended on peroxisomal fission factors, such as Dynamin-like protein 1 (DLP1) and mitochondrial fission factor (Mff), because the fission did not occur in cells treated with siRNA against such fission factors
Pex11pb has been implicated in docosahexaenoic acid (DHA)-induced peroxisomal fission in acyl-CoA oxidase (AOx)-deficient cells (Itoyama et al, 2012)

Summary

Introduction

Peroxisomes are single membrane-bound organelles that are involved in long-chain fatty acid oxidation, plasmalogen synthesis, and ROS elimination (van den Bosch et al, 1992; Wanders and Waterham, 2006). Knockdown or mutation of DLP1, Fis, and Mff results in fission-deficient, elongated peroxisomes (Koch et al, 2003; Koch et al, 2004; Koch et al, 2005; Tanaka et al, 2006; Kobayashi et al, 2007; Waterham et al, 2007; Gandre-Babbe and van der Bliek, 2008; Otera et al, 2010; Itoyama et al, 2013). Spherical peroxisomes require elongation steps prior to fission (Itoyama et al, 2012), which mitochondria do not

Methods

Results

Conclusion