title: Export-deficient monoubiquitinated PEX5 triggers peroxisome removal in SV40 large T antigen-transformed mouse embryonic fibroblasts.
abstract: Peroxisomes are ubiquitous cell organelles essential for human health. To maintain a healthy cellular environment, dysfunctional and superfluous peroxisomes need to be selectively removed. Although emerging evidence suggests that peroxisomes are mainly degraded by pexophagy, little is known about the triggers and molecular mechanisms underlying this process in mammalian cells. In this study, we show that PEX5 proteins fused to a bulky C-terminal tag trigger peroxisome degradation in SV40 large T antigen-transformed mouse embryonic fibroblasts. In addition, we provide evidence that this process is autophagy-dependent and requires monoubiquitination of the N-terminal cysteine residue that marks PEX5 for recycling. As our findings also demonstrate that the addition of a bulky tag to the C terminus of PEX5 does not interfere with PEX5 monoubiquitination but strongly inhibits its export from the peroxisomal membrane, we hypothesize that such a tag mimics a cargo protein that cannot be released from PEX5, thus keeping monoubiquitinated PEX5 at the membrane for a sufficiently long time to be recognized by the autophagic machinery. This in turn suggests that monoubiquitination of the N-terminal cysteine of peroxisome-associated PEX5 not only functions to recycle the peroxin back to the cytosol, but also serves as a quality control mechanism to eliminate peroxisomes with a defective protein import machinery.
authors.affiliation: a Laboratory of Lipid Biochemistry and Protein Interactions; Department of Cellular and Molecular Medicine; University of Leuven - KU Leuven ; Leuven , Belgium.
authors.forename: Marcus
authors.initials: M
authors.lastname: Nordgren
authors.forename: Tânia
authors.initials: T
authors.lastname: Francisco
authors.forename: Celien
authors.initials: C
authors.lastname: Lismont
authors.forename: Lore
authors.initials: L
authors.lastname: Hennebel
authors.forename: Chantal
authors.initials: C
authors.lastname: Brees
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
authors.forename: Paul P
authors.initials: PP
authors.lastname: Van Veldhoven
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Azevedo
authors.forename: Marc
authors.initials: M
authors.lastname: Fransen
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000737:chemistry*; D001343:Autophagy; D003545:Cysteine / Q000737:chemistry; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000032:analysis; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000378:metabolism*; D010641:Phenotype; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D000952:Antigens, Polyomavirus Transforming; C000614264:PEX5 protein, human; D000074435:Peroxisome-Targeting Signal 1 Receptor; C000614265:Pex5 protein, mouse; D018160:Receptors, Cytoplasmic and Nuclear; D004247:DNA; D003545:Cysteine
keywords: PEX5; peroxisome; pexophagy; protein import; receptor recycling; selective autophagy; ubiquitin