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Inverse Agonist-Induced Signaling and Down-Regulation of the Platelet-Activating Factor Receptor

Inverse Agonist-Induced Signaling and Down-Regulation of the Platelet-Activating Factor Receptor

Denis J Dupré, Charles Thompson, Zhangguo Chen, Simon Rollin, Jean-François Larrivée, Christian Le Gouill, Marek Rola-Pleszczynski, Jana Stanková

Cell Signal. 2007 Oct;19(10):2068-79.

PMID: 17609120

Abstract:

Platelet-activating factor (PAF) is a potent phospholipid mediator involved in several diseases such as allergic asthma, atherosclerosis and psoriasis. The human PAF receptor (PAFR) is a member of the G-protein-coupled receptor family. Following stimulation, PAFR becomes rapidly desensitized; this refractory state is dependent on PAFR phosphorylation, internalization and down-regulation. In this report, we show that the PAFR inverse agonist, WEB2086, can induce phosphorylation and down-regulation of PAFR. Using selective inhibitors, we determined that the agonist, PAF, and WEB2086 could induce phosphorylation of PAFR by PKC. Moreover, dominant-negative (DN) mutant of PKC isoforms beta inhibited WEB2086-stimulated PAFR phosphorylation, whereas PAF-stimulated phosphorylation was inhibited by DN PKCalpha and delta. WEB2086 also induced PAFR down-regulation which could be blocked by PKC inhibitors and by DN PKCbeta. WEB2086-induced down-regulation was dynamin-dependent but arrestin-independent. Unlike PAF, WEB2086-stimulated intracellular trafficking of PAFR was independent of Rab5. Specific inhibitors of lysosomal proteases and of proteasomes were both effective in reducing WEB2086-induced PAFR down-regulation, indicating the importance of receptor targeting to both lysosomes and proteasomes in long-term cell desensitization to WEB2086. These results indicate that although both agonists and inverse agonists induce receptor PAFR down-regulation, this may be accomplished through different signal transduction and trafficking pathways.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP105219565	WEB2086		105219-56-5	Price

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