title: Pex3p initiates the formation of a preperoxisomal compartment from a subdomain of the endoplasmic reticulum in Saccharomyces cerevisiae.
abstract: Peroxisomes are dynamic organelles that often proliferate in response to compounds that they metabolize. Peroxisomes can proliferate by two apparent mechanisms, division of preexisting peroxisomes and de novo synthesis of peroxisomes. Evidence for de novo peroxisome synthesis comes from studies of cells lacking the peroxisomal integral membrane peroxin Pex3p. These cells lack peroxisomes, but peroxisomes can assemble upon reintroduction of Pex3p. The source of these peroxisomes has been the subject of debate. Here, we show that the amino-terminal 46 amino acids of Pex3p of Saccharomyces cerevisiae target to a subdomain of the endoplasmic reticulum and initiate the formation of a preperoxisomal compartment for de novo peroxisome synthesis. In vivo video microscopy showed that this preperoxisomal compartment can import both peroxisomal matrix and membrane proteins leading to the formation of bona fide peroxisomes through the continued activity of full-length Pex3p. Peroxisome formation from the preperoxisomal compartment depends on the activity of the genes PEX14 and PEX19, which are required for the targeting of peroxisomal matrix and membrane proteins, respectively. Our findings support a direct role for the endoplasmic reticulum in de novo peroxisome formation.
authors.affiliation: Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
authors.forename: Yuen Yi C
authors.initials: YY
authors.lastname: Tam
authors.forename: Andrei
authors.initials: A
authors.lastname: Fagarasanu
authors.forename: Monica
authors.initials: M
authors.lastname: Fagarasanu
authors.forename: Richard A
authors.initials: RA
authors.lastname: Rachubinski
mesh_terms: D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005838:Genotype; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D026901:Membrane Transport Proteins; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D000074401:Peroxins; D020675:Peroxisomes / Q000737:chemistry / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D013347:Subcellular Fractions; D013696:Temperature
chemical_list: D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C499195:PEX14 protein, S cerevisiae; C109779:PEX19 protein, S cerevisiae; C070895:PEX3 protein, S cerevisiae; D000074401:Peroxins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins