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J. Biol. Chem., Vol. 281, Issue 18, 12817-12823, May 5, 2006

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The Dynamin-like Protein Vps1p of the Yeast Saccharomyces cerevisiae Associates with Peroxisomes in a Pex19p-dependent Manner^*

Franco J. Vizeacoumar¹, Wanda N. Vreden, Monica Fagarasanu¹, Gary A. Eitzen², John D. Aitchison, and Richard A. Rachubinski³

From the Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada and the Institute for Systems Biology, Seattle, Washington 98103

Dynamins and dynamin-like proteins play important roles in organelle division. In Saccharomyces cerevisiae, the dynamin-like protein Vps1p (vacuolar protein sorting protein 1) is involved in peroxisome fission, as cells deleted for the VPS1 gene contain reduced numbers of enlarged peroxisomes. What relationship Vps1p has with peroxisomes remains unclear. Here we show that Vps1p interacts with Pex19p, a peroxin that acts as a shuttling receptor for peroxisomal membrane proteins or as a chaperone assisting the assembly/stabilization of proteins at the peroxisome membrane. Vps1p contains two putative Pex19p recognition sequences at amino acids 509-523 and 633-647. Deletion of the first (but not the second) sequence results in reduced numbers of enlarged peroxisomes in cells, as in vps1 cells. Deletion of either sequence has no effect on vacuolar morphology or vacuolar protein sorting, suggesting that the peroxisome and vacuole biogenic functions of Vps1p are separate and separable. Substitution of proline for valine at position 516 of Vps1p abrogates Pex19p binding and gives the peroxisome phenotype of vps1 cells. Microscopic analysis showed that overexpression of Pex19p or redirection of Pex19p to the nucleus does not affect the normal cellular distribution of Vps1p in the cytosol and in punctate structures that are not peroxisomes, suggesting that Pex19p does not function in targeting Vps1p to peroxisomes. Subcellular fractionation showed that a fraction of Vps1p is associated with peroxisomes and that deletion or mutation of the first Pex19p recognition sequence abrogates this association. Our results are consistent with Pex19p acting as a chaperone to stabilize the association of Vps1p with peroxisomes and not as a receptor involved in targeting Vps1p to peroxisomes.

Received for publication, January 13, 2006 , and in revised form, March 6, 2006.

^* This work was supported by Grant MOP-15131 from the Canadian Institutes of Health Research (CIHR) (to R. A. R.) and Grant GM067228 from the National Institutes of Health (to J. D. A.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Recipient of a studentship from the Alberta Heritage Foundation for Medical Research (AHFMR).

² A CIHR new investigator and an AHFMR scholar.

³ Holder of a Canada research chair in cell biology and an international research scholar of the Howard Hughes Medical Institute. To whom correspondence should be addressed: Dept. of Cell Biology, University of Alberta, Medical Sciences Bldg. 5-14, Edmonton, Alberta T6G 2H7, Canada. Tel.: 780-492-9868; Fax: 780-492-9278; E-mail: rick.rachubinski{at}ualberta.ca.

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