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Originally published as MBC in Press, 10.1091/mbc.E06-07-0618 on February 21, 2007

Vol. 18, Issue 5, 1570-1585, May 2007

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Caveolin 2 Regulates Endocytosis and Trafficking of the M1 Muscarinic Receptor in MDCK Epithelial CellsFormula

Miriam Shmuel*, Efrat Nodel-Berner*, Tehila Hyman, Alexander Rouvinski, and Yoram Altschuler

Department of Pharmacology, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel

Submitted July 24, 2006; Revised February 1, 2007; Accepted February 12, 2007
Monitoring Editor: Keith Mostov

Clathrin and caveolins are known for their involvement in the internalization of numerous receptors. Here we show that in polarized epithelial Madin-Darby canine kidney cells, both the clathrin machinery and caveolins are involved in the endocytosis and delivery to the plasma membrane (PM) of the M1 muscarinic acetylcholine receptor (mAChR). We initially localized this receptor to the lateral membrane, where it accumulates proximal to the tight junctions. From there it is internalized through the clathrin-mediated pathway. In addition, the receptor may associate on the PM with caveolin (cav) 2 or in intracellular compartments with either cav 2, or monomeric or oligomeric cav 1. Association of the PM M1 mAChR with cav 2 inhibits receptor endocytosis through the clathrin-mediated pathway or retains the receptor in an intracellular compartment. This intracellular association attenuates receptor trafficking. Expression of cav 1 with cav 2 rescues the latter's inhibitory effect. The caveolins stimulate M1 mAChR oligomerization thus maintaining a constant amount of monomeric receptor. These results provide evidence that caveolins play a role in the attenuation of the M1 muscarinic receptor's intracellular trafficking to and from the PM.

This article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E06-07-0618) on February 21, 2007.

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

* These authors contributed equally to this work.

Address correspondence to: Yoram Altschuler (yoram.altschuler{at}ekmd.huji.ac.il)

Abbreviations used: AP, apical; BL, basolateral; CME, clathrin-mediated endocytosis; cav 1 and 2, caveolin 1 and 2; DRM, detergent-resistant membrane; MDCK, Madin-Darby canine kidney; PM, plasma membrane; GPCR, G-protein–coupled receptor; mAChR, muscarinic acetylcholine receptor.






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