A vesicle carrier that mediates peroxisome protein traffic from the endoplasmic reticulum

Abstract

Pex19p, a soluble cytoplasmic transport protein, is required for the traffic of the peroxisomal membrane proteins Pex3p and Pex15p from the endoplasmic reticulum (ER) to the peroxisome. We documented Pex15p traffic from the ER using a chimeric protein containing a C-terminal glycosylation acceptor peptide. Pex15Gp expressed in wild-type yeast cells is N-glycosylated and functions properly in the peroxisome. In contrast, pex19Δ -mutant cells accumulate the glycoprotein Pex15Gp in the ER. We developed a cell-free preperoxisomal vesicle-budding reaction in which Pex15Gp and Pex3p are packaged into small vesicles in the presence of cytosol, Pex19p, and ATP. Secretory vesicle budding (COPII) detected by the packaging of a SNARE protein (soluble N-ethylmaleimide-sensitive attachment protein receptor) occurs in the same incubation but does not depend on Pex19p. Conversely a dominant GTPase mutant Sar1p which inhibits COPII has no effect on Pex3p packaging. Pex15Gp and Pex3p budded vesicles sediment as low-buoyant-density membranes on a Nycodenz gradient and copurify by affinity isolation using native but not Triton X-100–treated budded vesicles. ER–peroxisome transport vesicles appear to rely on a novel budding mechanism requiring Pex19p and additional unknown factors.

Endoplasmic Reticulum Structure and Interconnections with Other Organelles

“…The peroxisome is a unique organelle that receives much of its starting material, including lipids and peroxisomal membrane proteins, from the ER for de novo biogenesis (Kim et al 2006;Lam et al 2010). Past results show that both vesicular and nonvesicular transport of lipids and proteins from the ER are required for proper peroxisomal formation and maintenance (Raychaudhuri and Prinz 2008;Lam et al 2010;Agrawal et al 2011;van der Zand et al 2012).…”

“…Past results show that both vesicular and nonvesicular transport of lipids and proteins from the ER are required for proper peroxisomal formation and maintenance (Raychaudhuri and Prinz 2008;Lam et al 2010;Agrawal et al 2011;van der Zand et al 2012). In vitro ER-peroxisome lipid transfer assays also show nonvesicular transport between the membrane compartments; however, the proteins mediating this process remain to be identified (Raychaudhuri and Prinz 2008).…”

Expanding Proteostasis by Membrane Trafficking Networks

“…3A,B) is evident, for example, from the existence of compartments such as (1) the sarcoplasmic reticulum, a specialized ER subdomain that manages Ca 2þ -sensitive folding and signaling pathways in muscle (Zhao et al 2011); (2) peroxisomes that are specialized for managing oxidative stress (Lam et al 2011;Dimitrov et al 2013;Grimm et al 2012). Moreover, endosomal/lysosomal compartments generate a reduced pH environment to promote destabilization and metastability of the protein fold for recycling and/or degradation by the lysosome (Wickner 2010).…”

“…Indeed, the flexibility of TPN-based TRaCKS suggests that the plethora of emerging "unconventional" pathways may have a common framework that simply reflects the versatility of TPN function-and, thus, may not be so unconventional. These now include, for example, the genesis of autophagic membranes from the ER (Gee et al 2011;Deretic et al 2012) and the identification of multiple unanticipated compartment linkages including ER-phagosome (Hubber and Roy 2010;Huang et al 2011), ER-mitochondrial (Friedman et al 2011;Westermann 2011), Golgi-cell surface (Golgi-bypass) (Nickel 2010; Grieve and Rabouille 2011), ER-peroxisome (Lam et al 2011;Dimitrov et al 2013), preGolgi -endosome (Saraste et al 2009), and intranuclear-cytoplasmic trafficking pathways (Montpetit and Weis 2012;Speese et al 2012). In this regard, Golgi structure/function relationships have been a particularly acute area of controversy with many models (Morre and Ovtracht 1977;Emr et al 2009;Papanikou and Glick 2009;Pfeffer 2010;Glick and Luini 2011;Mironov and Beznoussenko 2011;Munro 2011b).…”

Clearing tail-anchored proteins from mitochondria

“…1A). The peroxin Pex15 is initially inserted into the ER via the GET pathway and then transferred to peroxisomes via vesicular transport (8,12,13). Other tailanchored proteins use an ER-independent pathway, where the precursors are targeted to peroxisomes via the Pex19 cytosolic chaperone and the peroxisome-resident receptor Pex3 (14).…”