Peroxisomal membrane proteins are properly targeted to peroxisomes in the absence of COPI- and COPII-mediated vesicular transport.
The classic model for peroxisome biogenesis states that new peroxisomes arise by the fission of pre-existing ones and that peroxisomal matrix and membrane proteins are recruited directly from the cytosol. Recent studies challenge this model and suggest that some peroxisomal membrane proteins might traffic via the endoplasmic reticulum to peroxisomes. We have studied the trafficking in human fibroblasts of three peroxisomal membrane proteins, Pex2p, Pex3p and Pex16p, all of which have been suggested to transit the endoplasmic reticulum before arriving in peroxisomes. Here, we show that targeting of these peroxisomal membrane proteins is not affected by inhibitors of COPI and COPII that block vesicle transport in the early secretory pathway. Moreover, we have obtained no evidence for the presence of these peroxisomal membrane proteins in compartments other than peroxisomes and demonstrate that COPI and COPII inhibitors do not affect peroxisome morphology or integrity. Together, these data fail to provide any evidence for a role of the endoplasmic reticulum in peroxisome biogenesis.
Voorn-Brouwer
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Department of Biochemistry, University of Amsterdam, Academic Medical Center, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands.
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D018528:ATP-Binding Cassette Transporters; D020126:Brefeldin A / Q000494:pharmacology; D022181:COP-Coated Vesicles / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D020755:Coat Protein Complex I / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts; D005656:Fungal Proteins; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008074:Lipoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D000074401:Peroxins; D000074428:Peroxisomal Biogenesis Factor 2; D020675:Peroxisomes / Q000187:drug effects / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects
C063305:ABCD3 protein, human; D018528:ATP-Binding Cassette Transporters; D020755:Coat Protein Complex I; D005656:Fungal Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; C486345:PEX16 protein, human; D000074401:Peroxins; C113138:Pex3 protein, human; D000074428:Peroxisomal Biogenesis Factor 2; D020126:Brefeldin A