Inhibitors of COPI and COPII do not block PEX3-mediated peroxisome synthesis.
In humans, defects in peroxisome biogenesis are the cause of lethal diseases typified by Zellweger syndrome. Here, we show that inactivating mutations in human PEX3 cause Zellweger syndrome, abrogate peroxisome membrane synthesis, and result in reduced abundance of peroxisomal membrane proteins (PMPs) and/or mislocalization of PMPs to the mitochondria. Previous studies have suggested that PEX3 may traffic through the ER en route to the peroxisome, that the COPI inhibitor, brefeldin A, leads to accumulation of PEX3 in the ER, and that PEX3 overexpression alters the morphology of the ER. However, we were unable to detect PEX3 in the ER at early times after expression. Furthermore, we find that inhibition of COPI function by brefeldin A has no effect on trafficking of PEX3 to peroxisomes and does not inhibit PEX3-mediated peroxisome biogenesis. We also find that inhibition of COPII-dependent membrane traffic by a dominant negative SAR1 mutant fails to block PEX3 transport to peroxisomes and PEX3-mediated peroxisome synthesis. Based on these results, we propose that PEX3 targeting to peroxisomes and PEX3-mediated peroxisome membrane synthesis may occur independently of COPI- and COPII-dependent membrane traffic.
South
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Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Sacksteder
K A
KA
Li
X
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Liu
Y
Y
Gould
S J
SJ
D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D020755:Coat Protein Complex I / Q000187:drug effects / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D000074401:Peroxins; D020675:Peroxisomes / Q000378:metabolism*; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013997:Time Factors; D033921:Vesicular Transport Proteins; D015211:Zellweger Syndrome / Q000235:genetics* / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D020755:Coat Protein Complex I; D005656:Fungal Proteins; D008565:Membrane Proteins; C070895:PEX3 protein, S cerevisiae; D000074401:Peroxins; D010750:Phosphoproteins; C106113:SEC31 protein, S cerevisiae; C406793:SPF1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins