A Combined Approach of Quantitative Interaction Proteomics and Live-cell Imaging Reveals a Regulatory Role for Endoplasmic Reticulum (ER) Reticulon Homology Proteins in Peroxisome Biogenesis

Christine David,Johannes Koch,Silke Oeljeklaus,Alexandra Laernsack,Sophie Melchior,Sebastian Wiese,Andreas Schummer,Ralf Erdmann,Bettina Warscheid,Cécile Brocard

doi:10.1074/mcp.m112.017830

Abstract

Peroxisome biogenesis initiates at the endoplasmic reticulum (ER) and maturation allows for the formation of metabolically active organelles. Yet, peroxisomes can also multiply by growth and division. Several proteins, called peroxins, are known to participate in these processes but little is known about their organization to orchestrate peroxisome proliferation. Here, we demonstrate that regulation of peroxisome proliferation relies on the integrity of the tubular ER network. Using a dual track SILAC-based quantitative interaction proteomics approach, we established a comprehensive network of stable as well as transient interactions of the peroxin Pex30p, an integral membrane protein. Through association with merely ER resident proteins, in particular with proteins containing a reticulon homology domain, and with other peroxins, Pex30p designates peroxisome contact sites at ER subdomains. We show that Pex30p traffics through the ER and segregates in punctae to which peroxisomes specifically append, and we ascertain its transient interaction with all subunits of the COPI coatomer complex suggesting the involvement of a vesicle-mediated transport. We establish that the membrane protein Pex30p facilitates the connection of peroxisomes to the ER. Taken together, our data indicate that Pex30p-containing protein complexes act as focal points from which peroxisomes can form and that the tubular ER architecture organized by the reticulon homology proteins Rtn1p, Rtn2p and Yop1p controls this process.

Highlights

From the ‡University of Vienna, Max F
To test whether Pex30p acts in concert with these factors to maintain the steady state level of peroxisomes, we evaluated the total number of peroxisomes per cell in different yeast mutants incubated in oleic acid-containing medium
Our findings expand the current insights into peroxisome proliferation by demonstrating for the first time that the control of the peroxisomal number per cell relies on proteins residing in the endoplasmic reticulum (ER) and on the integrity of the cortical ER tubular architecture

Summary

Introduction

From the ‡University of Vienna, Max F. To test whether Pex30p acts in concert with these factors to maintain the steady state level of peroxisomes, we evaluated the total number of peroxisomes per cell in different yeast mutants incubated in oleic acid-containing medium (Fig. 1A).

Results

Conclusion