Activation and translocation of PKCdelta is necessary for VEGF-induced ERK activation through KDR in HEK293T cells |
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Authors: | Kuriyama Masamitsu Taniguchi Taizo Shirai Yasuhito Sasaki Atsuo Yoshimura Akihiko Saito Naoaki |
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Institution: | Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan. |
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Abstract: | VEGF-KDR/Flk-1 signal utilizes the phospholipase C-gamma-protein kinase C (PKC)-Raf-MEK-ERK pathway as the major signaling pathway to induce gene expression and cPLA2 phosphorylation. However, the spatio-temporal activation of a specific PKC isoform induced by VEGF-KDR signal has not been clarified. We used HEK293T (human embryonic kidney) cells expressing transiently KDR to examine the activation mechanism of PKC. PKC specific inhibitors and human PKCdelta knock-down using siRNA method showed that PKCdelta played an important role in VEGF-KDR-induced ERK activation. Myristoylated alanine-rich C-kinase substrate (MARCKS) translocates from the plasma membrane to the cytoplasm depending upon phosphorylation by PKC. Translocation of MARCKS-GFP induced by VEGF-KDR stimulus was blocked by rottlerin, a PKCdelta specific inhibitor, or human PKCdelta siRNA. VEGF-KDR stimulation did not induce ERK phosphorylation in human PKCdelta-knockdown HEK293T cells, but co-expression of rat PKCdelta-GFP recovered the ERK phosphorylation. Y311/332F mutant of rat PKCdelta-GFP which cannot be activated by tyrosine-phosphorylation but activated by DAG recovered the ERK phosphorylation, while C1B-deletion mutant of rat PKCdelta-GFP, which can be activated by tyrosine-phosphorylation but not by DAG, failed to recover the ERK phosphorylation in human PKCdelta-knockdown HEK293T cell. These results indicate that PKCdelta is involved in VEGF-KDR-induced ERK activation via C1B domain. |
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Keywords: | Vascular endothelial growth factor-A KDR/Flk-1 HEK293T cells Phospholipase C-γ Protein kinase C ERK GFP Myristoylated alanine-rich C kinase substrate C1B domain |
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