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Vol. 17, Issue 4, 1593-1605, April 2006

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Cholesterol Is Required for Efficient Endoplasmic Reticulum-to-Golgi Transport of Secretory Membrane Proteins

Andrew Ridsdale ^*, Maxime Denis ^*, Pierre-Yves Gougeon ^*, Johnny K. Ngsee ^*, John F. Presley , and Xiaohui Zha ^*

^* Ottawa Health Research Institute and University of Ottawa, Ottawa, Ontario K1Y 4E9, Canada; Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 2B2, Canada

Submitted February 7, 2005; Revised January 19, 2006; Accepted January 20, 2006
Monitoring Editor: Sean Munro

Although cholesterol is synthesized in the endoplasmic reticulum (ER), compared with other cellular membranes, ER membrane has low cholesterol (3–6%). Most of the molecular machinery that regulates cellular cholesterol homeostasis also resides in the ER. Little is known about how cholesterol itself affects the ER membrane. Here, we demonstrate that acute cholesterol depletion in ER membranes impairs ER-to-Golgi transport of secretory membrane proteins. Cholesterol depletion is achieved by a brief inhibition of cholesterol synthesis with statins in cells grown in cholesterol-depleted medium. We provide evidence that secretory membrane proteins vesicular stomatitis virus glycoprotein and scavenger receptor A failed to be efficiently transported from the ER upon cholesterol depletion. Fluorescence photobleaching recovery experiments indicated that cholesterol depletion by statins leads to a severe loss of lateral mobility on the ER membrane of these transmembrane proteins, but not loss of mobility of proteins in the ER lumen. This impaired lateral mobility is correlated with impaired ER-to-Golgi transport. These results provide evidence for the first time that cholesterol is required in the ER membrane to maintain mobility of membrane proteins and thus protein secretion.

Abbreviations used: SREBP, sterol regulatory element–binding protein.

The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).

Address correspondence to: Xiaohui Zha (xzha{at}ohri.ca).

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