Article
- The EMBO Journal (2006) 25, 2953 - 2965
- doi:10.1038/sj.emboj.7601205
Published online: 22 June 2006
Subject Category:
Sterols regulate ER-export dynamics of secretory cargo protein ts-O45-G
Heiko Runz1,2, Kota Miura1, Matthias Weiss3 and Rainer Pepperkok1
- Cell Biology & Cell Biophysics Programme, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
- Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany
- Cellular Biophysics Group (BIOMS), German Cancer Research Center, Heidelberg, Germany
Correspondence to:
Heiko RunzRainer Pepperkok, Cell Biology & Cell Biophysics Programme, European Molecular Biology Laboratory (EMBL), Meyerhofstr. 1, Heidelberg 69117, Germany. Tel.: +49 6221 387 332; Fax: +49 6221 387 306; E-mails: E-mail: runz@embl.de or pepperko@embl-heidelberg.de
Received 14 October 2005; Accepted 31 May 2006
Abstract
Alterations in endoplasmic reticulum (ER) cholesterol are fundamental for a variety of cellular processes such as the regulation of lipid homeostasis or efficient protein degradation. We show that reduced levels of cellular sterols cause a delayed ER-to-Golgi transport of the secretory cargo membrane protein ts-O45-G and a relocation to the ER of an endogenous protein cycling between the ER and the Golgi complex. Transport inhibition is characterized by a delay in the accumulation of ts-O45-G in ER-exit sites (ERES) and correlates with a reduced mobility of ts-O45-G within ER membranes. A simple mathematical model describing the kinetics of ER-exit predicts that reduced cargo loading to ERES and not the reduced mobility of ts-O45-G accounts for the delayed ER-exit and arrival at the Golgi. Consistent with this, membrane turnover of the COPII component Sec23p is delayed in sterol-depleted cells. Altogether, our results demonstrate the importance of sterol levels in COPII mediated ER-export.
Keywords:
- cholesterol,
- ER exit sites,
- membrane trafficking,
- modelling,
- photobleaching
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