| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||
* Immunology Division, Department of Pediatrics, and
Department of Pharmacology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Canada
Certain proteins, including receptors and signaling molecules, are known to be enriched in caveolae and lipid rafts. Caveolin-1, the major structural protein of caveolae, specifically interacts with many signaling molecules and, thus, caveolae and lipid rafts are often seen as preassembled signaling platforms. A potential binding site for caveolin-1 is present in the platelet-activating factor receptor (PAFR) sequence, and many downstream signaling components of PAFR activation preferentially localize in caveolae. The aim of this study was to investigate whether the PAFR was localized in caveolae/lipid raft domains and, if so, what would be the significance of such localization for PAFR signaling. In this study, we demonstrate that PAFR localizes within membrane microdomains, in close proximity to caveolin-1 in living cells, with potential interaction through a caveolin-1-binding sequence in the PAFR C terminus. Caveolin-1, however, is not essential for PAFR localization in lipid rafts. Disruption of caveolae/lipid rafts with methyl-β-cyclodextrin markedly reduced PAF-triggered inositol phosphate production and cytosolic calcium flux, suggesting that PAFR signaling through the G
q protein was critically dependent on integrity of lipid rafts and/or caveolae. Interestingly, whereas in caveolin-1-expressing cells lipid raft disruption markedly decreased PAFR-mediated activation of the ERK/MAPK pathway, in cells lacking caveolae, such as leukocytes, lipid raft disruption had either the same inhibitory effect (Ramos B cells) or no effect (monocytes) on PAFR capacity to signal through the ERK/MAPK pathway. In conclusion, PAFR appears to localize within caveolae or lipid rafts in different cell types, and this location may be important for specific signaling events.
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 This work was supported by grants from the Canadian Institutes of Health Research (to G.B., J.S., and M.R.-P.) and by a Canada Research Chair in Inflammation (to M.R.-P.). G.B., J.S., and M.R.-P. are members of the Fonds de la recherche en santé du Québec-funded Étienne-LeBel Clinical Research Center.
2 Address correspondence and reprint requests to Dr. Marek Rola-Pleszczynski, Immunology Division, Department of Pediatrics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001 North 12th Avenue, Sherbrooke, QC Canada J1H 5N4. E-mail address: marek.rola-pleszczynski{at}usherbrooke.ca
3 Abbreviations used in this paper: PAF, platelet-activating factor; AEBSF, 4-(2-aminoethyl)benzenesulfonyl fluoride; BRET, bioluminescence resonance energy transfer; [Ca2+]i, intracellular Ca2+ concentration; CD, methyl-β-cyclodextrin; CHO, Chinese hamster ovary; EtOH, ethanol; GPCR, G protein-coupled receptor; HA, hemagglutinin; IP, inositol phosphate; WT, wild type.
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
