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EGFR Transactivation (egfr + transactivation)
Selected AbstractsCardioprotection of bradykinin at reperfusion involves transactivation of the epidermal growth factor receptor via matrix metalloproteinase-8ACTA PHYSIOLOGICA, Issue 4 2009C. Methner Abstract Aim:, The endogenous autacoid bradykinin (BK) reportedly reduces myocardial infarct size when given exogenously at reperfusion. Muscarinic and opioid G-protein-coupled receptors are equally protective and have been shown to couple through a matrix metalloproteinase (MMP)-dependent transactivation of the epidermal growth factor receptor (EGFR). Here we test whether BK protects the rat heart through the EGFR by an MMP-dependent pathway. Methods:, Infarct size was measured in isolated perfused rat hearts undergoing 30 min regional ischaemia followed by 120 min reperfusion. In additional studies HL-1 cardiomyocytes were loaded with tetramethylrhodamine ethyl to measure their mitochondrial membrane potential (,m). Adding the calcium ionophore calcimycin, causes ,m-collapse presumably due to calcium-induced mitochondrial permeability transition. Results:, As expected, BK (100 nmol L,1) started 5 min prior to reperfusion reduced infarct size from 38.9 ± 2.0% of the ischaemic zone in control hearts to 22.2 ± 3.3% (P < 0.001). Co-infusing the EGFR inhibitor AG1478, the broad-spectrum MMP-inhibitor GM6001, or a highly selective MMP-8 inhibitor abolished BK's protection, thus suggesting an MMP-8-dependent EGFR transactivation in the signalling. Eighty minutes of exposure to calcimycin reduced the mean cell fluorescence to 37.4 ± 1.8% of untreated cells while BK could partly preserve the fluorescence and, hence, protect the cells (50.5 ± 2.3%, P < 0.001). The BK-induced mitochondrial protection could again be blocked by AG1478, GM6001 and MMP-8 inhibitor. Finally, Western blotting revealed that BK's protection was correlated with increased phosphorylation of EGFR and its downstream target Akt. Conclusion:, These results indicate that BK at reperfusion triggers its protective signalling pathway through MMP-8-dependent transactivation of the EGFR. [source] Bradykinin-induced p42/p44 MAPK phosphorylation and cell proliferation via Src, EGF receptors, and PI3-K/Akt in vascular smooth muscle cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2005Chuen-Mao Yang In our previous study, bradykinin (BK) exerts its mitogenic effect through Ras/Raf/MEK/MAPK pathway in vascular smooth muscle cells (VSMCs). In addition to this pathway, the non-receptor tyrosine kinases (Src), EGF receptor (EGFR), and phosphatidylinositol 3-kinase (PI3-K) have been implicated in linking a variety of G-protein coupled receptors to MAPK cascades. Here, we investigated whether these different mechanisms participating in BK-induced activation of p42/p44 MAPK and cell proliferation in VSMCs. We initially observed that BK- and EGF-dependent activation of Src, EGFR, Akt, and p42/p44 MAPK and [3H]thymidine incorporation were mediated by Src and EGFR, because the Src inhibitor PP1 and EGFR kinase inhibitor AG1478 abrogated BK- and EGF-dependent effects. Inhibition of PI3-K by LY294002 attenuated BK-induced Akt and p42/p44 MAPK phosphorylation and [3H]thymidine incorporation, but had no effect on EGFR phosphorylation, suggesting that EGFR may be an upstream component of PI3-K/Akt and MAPK in these responses. This hypothesis was supported by the tranfection with dominant negative plasmids of p85 and Akt which significantly attenuated BK-induced Akt and p42/p44 MAPK phosphorylation. Pretreatment with U0126 (a MEK1/2 inhibitor) attenuated the p42/p44 MAPK phosphorylation and [3H]thymidine incorporation stimulated by BK, but had no effect on Akt activation. Moreover, BK-induced transactivation of EGFR and cell proliferation was blocked by matrix metalloproteinase inhibitor GM6001. These results suggest that, in VSMCs, the mechanism of BK-stimulated activation of p42/p44 MAPK and cell proliferation was mediated, at least in part, through activation of Src family kinases, EGFR transactivation, and PI3-K/Akt. Copyright © 2004 Wiley-Liss, Inc. [source] Stress kinase p38 mediates EGFR transactivation by hyperosmolar concentrations of sorbitolJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2002Hao Cheng Activation of the epidermal growth factor receptor (EGFR) has been shown to occur by ligand-dependent and ligand-independent mechanisms. Different molecular mechanisms have been found to be responsible for ligand-independent receptor transactivation. Here, we show that hyperosmolar concentrations of sorbitol activate the EGFR in human keratinocytes. Experiments using specific inhibitors of EGFR phosphorylation show that the increased amount of activated receptors is the result of a decreased rate of dephosphorylation. Furthermore, sorbitol treatment results in a strong activation of stress kinase p38. Treatment of the cells with SB203580, a known inhibitor of p38 , and , kinases, results in impairment of receptor activation, indicating that the stress kinase is involved in receptor activation modulation. This is further reinforced by experiments showing that addition of Toxin B, known to be an inhibitor of the small Rho GTPases rac1, cdc42, and Rho A/B, to the cells results in a strong induction of EGFR activation. Our results point, therefore, to a mechanism by which osmotic shock activates EGFR through the small Rho GTPases-p38 stress kinase pathway. © 2002 Wiley-Liss, Inc. [source] Activation of MEK/ERK and PI3K/Akt pathways by fibronectin requires integrin ,v-mediated ADAM activity in hepatocellular carcinoma: A novel functional target for gefitinibCANCER SCIENCE, Issue 2 2006Mitsuhiro Matsuo We have shown that the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib (,Iressa', ZD1839) inhibits the development of intrahepatic metastases of hepatocellular carcinoma CBO140C12, and EGFR transactivation by tumor necrosis factor-, is a possible target of gefitinib. In the present study, we focused on the fibronectin (FN)-dependent signaling pathway to further elucidate the antimetastatic activity of gefitinib in CBO140C12 cells. We initially observed that FN induced activation of extracellular signal-regulated kinase (ERK), p38 and Akt, as well as cell proliferation and CBO140C12 cell invasion. These responses were mediated by EGFR tyrosine kinase, because gefitinib inhibited these effects of FN. FN-induced ERK, p38 and Akt activation was partly blocked by the Arg-Gly-Asp (RGD)-pseudo-peptide FC-336, anti-,v integrin antibody RMV-7, the broad-spectrum matrix metalloprotease inhibitor GM6001 and the broad spectrum a disintegrin and metalloprotease (ADAM) inhibitor TAPI-1. But these inhibitors had no effect on EGF-induced signaling pathways, suggesting that integrins and ADAM may be upstream components of EGFR in these responses. These results suggest that FN-induced activation of ERK, p38, Akt, cell proliferation and invasion was mediated, at least in part, via integrins, ADAM and EGFR, and that this FN-induced signaling pathway might be involved in the antimetastatic activity of gefitinib. (Cancer Sci 2006; 97: 155 ,162) [source] | ||||||||||