| Title | CB1R-dependent activation of fyn tyrosine kinase and protein kinase C Delta, PKCδ, in lipid rafts | ||
| Authors | O. Asimaki¹, N. Sakellaridis² and D. Mangoura¹
1. Biomedical Research Foundation, Academy of Athens, Basic Neurosciences Division, Athens, Greece 2. Department of Pharmacology, School of Medicine, University of Thessaly, Larissa, Greece |
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| Citation | Asimaki, O., Sakellaridis, N. and Mangoura, D.: CB1R-dependent activation of fyn tyrosine kinase and protein kinase C Delta, PKCδ, in lipid rafts, Epitheorese Klin. Farmakol. Farmakokinet. 22(2): 109-112 (2008) | ||
| Publication Date | 23-25 May 2008 | ||
| Full Text Language | English | ||
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| Keywords | CB1R, ERK, lipid rafts, Fyn, PKC. | ||
| Other Terms | Review article | ||
| Summary | Cannabinoid 1 receptors (CB1Rs) are heptahelical transmembrane receptors which may exert their effects through the activation of the extracellular signal-regulated kinases (ERKs). We have previously shown that stably overexpressed CB1R in neuroblastoma cells (SH-SY5Y-CB1R cell line) is coupled to ERK activation via a mechanism that involves cannabinoid- induced transactivation of the EGF receptor and PKC activation. In a new line of experiments, EGFR transactivation by cannabinoid agonists was further supported by assessments of Ras activity. Ras assays revealed elevated Ras activity after Methanandamide treatment, which was abolished by the EGFR inhibitor AG1478. In analyzing this mechanism, we investigated the subcellular trafficking of the CB1R in basal conditions and in response to agonist stimulation in SH-SY5Y-CB1R cells. We found that under basal conditions, CB1R was mainly distributed in subcellular fractions which contain plasma-membrane, mitochondria or ER membranes, whereas after treatment with the CB1 agonist Methanandamide we observed redistribution of the receptor into the lipid rafts fractions. Moreover, we found that the activated (phosphorylated) species of EGFR also appeared in the lipid rafts after Methanandamide and importantly this effect was completely abolished by AG1478. To address what molecular events couple CB1R activation to ERK activation, we investigated whether members of Src family tyrosine kinases mediate this coupling. We found that PP1 and PP2 inhibitors of the Src family of tyrosine kinases in particular of Fyn kinase, abolish the methanandamide-dependent ERK activation. Furthermore, Methanandamide treatment induced tyrosine phosphorylation, an event that was inhibited by PP1, as well as by inhibitors of novel PKCs. In addition, Methanandamide-induced phosphorylation-activation of PKCs was also partially inhibited by Fyn and PKC inhibitors. Next, using immunoprecipitations we found that the novel PKC isoform delta, PKC5, was tyrosine-phosphorylated in response to Methanandamide treatment and that this tyrosine phosphorylation was abolished by PP1 and Ro31-8220 (an inhibitor of classic and novel PKCs) but not by Go6976 (an inhibitor of classic PKC isoforms). These results suggest that in CB1R signaling a) Fyn activation may lie upstream of PKC5, and b) a novel PKC isoform other than PKC5 activates Fyn which in turn activates PKC5. | ||
| References | 1. Macdonald J., Pike L.: A simplified method for the preparation of detergent-free lipid rafts. J. Lipid Res. 46: 1061-1067 (2005)
2. Mangoura D., et al.: Phosphorylation of neurofibromin by PKC is a possible molecular switch in EGF receptor signaling in neural cells. Oncogene 25: 735-745 (2006) 3. Chang et al.: Prolactin-induced cell proliferation in PC12 cells depends on JNK but not ERK activation. J. Biol. Chem. 275: 23326-23332 (2000) 4. Niv H., et al.: Activated K-Ras and H-Ras display different interactions with saturable non raft sites at the surface of live cells. J. Cell Biol. 157: 865-872 (2002) 5. Mineo C., et al.: Localization of epidermal growth factor- stimulated Ras/Raf-1 interaction to caveolae membrane. J. Biol. Chem. 271: 11930-11935 (1996) 6. Kasai A., et al.: Role of Src family tyrosine kinases in the down- regulation of epidermal growth factor signaling in PC12 cells. Genes to Cells 10: 1175-1187 (2005) 7. Galve-Roperh. I. et al.: Mechanism of extracellular signal- regulated kinase activation by the CB1 cannabinoid receptor. Mol. Pharmacol. 62: 1385-1392 (2002) 8. Derkinderen P. et al.: Regulation of extracellular signal-regulated kinase by cannabinoids in hippocampus. J. Neurosci. 23: 2371-2382 (2003) |
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| Relative Papers | |||
Online ISSN 1011-6575
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Articles published in this Journal are Indexed or Abstracted in: • Chemical Abstracts • Elsevier’s Bibliographic Databases: Scopus, EMBASE, EMBiology, Elsevier BIOBASE SCImago Journal and Country Rank Factor
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