Article

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

Department of Molecular and Cell Biology and Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 11/2010; 107(50):21523-8. DOI: 10.1073/pnas.1013397107
Source: PubMed

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.

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    • "Pex3 later on became the paradigm PMP to study the indirect targeting pathway via the ER (further details below). Several other PMPs have also been found to be directly associated with the ER, or structures emerging from the ER, in particular Pex16 in plants and mammals, and Pex15 and Pex22 in yeast [8] [16] [41]. 3. Peroxisomal biogenesis factor 19 (Pex19) "
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    • "Both the coat protein complex (LDBPK_ 322150) and ARF (LDBPK_312350 and LDBPK_312890) proteins have been detected in the present leishmanial glycosomal preparation. A complete set of proteins essential for heterotypic fusion reactions requires N-ethylmaleimidesensitive factor (NSF; LDBPK_200820), and soluble NSF attachment protein receptors (SNAREs; LDBPK_352760 and LDBPK_070570) (Lam et al., 2010) were also found in glycosomal fraction. Several Rab proteins, ras-like small GTPase, and GTP binding proteins that are essential regulators of vesicle trafficking (Gronemeyer et al., 2013) were also found in the proteomic analysis of glycosomes. "
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    • "First, fluorescently tagged, membrane anchored Pex proteins, notably Pex3 and Pex16, have been observed emerging from the ER in conditions where peroxisomes are either induced by growth conditions or in pulse-chase type of rescue experiments (Titorenko and Rachubinski, 1998; Hoepfner et al., 2005; Kragt et al., 2005; Tam et al., 2005; Kim et al., 2006; Motley and Hettema, 2007). Second, cell free budding assays from isolated ER have established some of the machinery required to bud Pex-containing vesicles in yeast Saccharomyces cerevisiae (Lam et al., 2010). In this case, the authors showed both Pex3p and Pex15p emerging within vesicles in a manner that depended on ATP and Pex19p, but not Sar1, a GTPase essential for anterograde COPII budding events. "
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