Nakaoka Yoshikazu, Nishida Keigo, Fujio Yasushi, Izumi Masahiro, Terai Kazuo, Oshima Yuichi, Sugiyama Shoko, Matsuda Satoshi, Koyasu Shigeo, Yamauchi-Takihara Keiko, Hirano Toshio, Kawase Ichiro, Hirota Hisao
Department of Molecular Medicine, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan.
Circ Res. 2003 Aug 8;93(3):221-9. doi: 10.1161/01.RES.0000085562.48906.4A. Epub 2003 Jul 10.
Grb2-associated binder-1 (Gab1) is a scaffolding/docking protein and contains a Pleckstrin homology domain and potential binding sites for Src homology (SH) 2 and SH3 domains. Gab1 is tyrosine phosphorylated and associates with protein tyrosine phosphatase SHP2 and p85 phosphatidylinositol 3-kinase on stimulation with various cytokines and growth factors, including interleukin-6. We previously demonstrated that interleukin-6-related cytokine, leukemia inhibitory factor (LIF), induced cardiac hypertrophy through gp130. In this study, we report the role of Gab1 in gp130-mediated cardiac hypertrophy. Stimulation with LIF induced tyrosine phosphorylation of Gab1, and phosphorylated Gab1 interacted with SHP2 and p85 in cultured cardiomyocytes. We constructed three kinds of adenovirus vectors, those carrying wild-type Gab1 (AdGab1WT), mutated Gab1 lacking SHP2 binding site (AdGab1F627/659), and beta-galactosidase (Adbeta-gal). Compared with cardiomyocytes infected with Adbeta-gal, longitudinal elongation of cardiomyocytes induced by LIF was enhanced in cardiomyocytes infected with AdGab1WT but inhibited in cardiomyocytes infected with AdGab1F627/659. Upregulation of BNP mRNA expression by LIF was evoked in cardiomyocytes infected with Adbeta-gal and AdGab1WT but not in cardiomyocytes infected with AdGab1F627/659. In contrast, Gab1 repressed skeletal alpha-actin mRNA expression through interaction with SHP2. Furthermore, activation of extracellular signal-regulated kinase 5 (ERK5) was enhanced in cardiomyocytes infected with AdGab1WT compared with cardiomyocytes infected with Adbeta-gal but repressed in cardiomyocytes infected with AdGab1F627/659. Coinfection of AdGab1WT with adenovirus vector carrying dominant-negative ERK5 abrogated longitudinal elongation of cardiomyocytes induced by LIF. Taken together, these findings indicate that Gab1-SHP2 interaction plays a crucial role in gp130-dependent longitudinal elongation of cardiomyoctes through activation of ERK5.
Grb2相关结合蛋白1（Gab1）是一种支架/对接蛋白，含有一个普列克底物蛋白同源结构域以及Src同源（SH）2和SH3结构域的潜在结合位点。在受到包括白细胞介素-6在内的多种细胞因子和生长因子刺激时，Gab1会发生酪氨酸磷酸化，并与蛋白酪氨酸磷酸酶SHP2和p85磷脂酰肌醇3激酶结合。我们之前证明，白细胞介素-6相关细胞因子白血病抑制因子（LIF）通过gp130诱导心肌肥大。在本研究中，我们报告了Gab1在gp130介导的心肌肥大中的作用。LIF刺激可诱导Gab1的酪氨酸磷酸化，磷酸化的Gab1在培养的心肌细胞中与SHP2和p85相互作用。我们构建了三种腺病毒载体，分别携带野生型Gab1（AdGab1WT）、缺乏SHP2结合位点的突变型Gab1（AdGab1F627/659）以及β-半乳糖苷酶（Adβ-gal）。与感染Adβ-gal的心肌细胞相比，感染AdGab1WT的心肌细胞中LIF诱导的心肌细胞纵向伸长增强，而感染AdGab1F627/659的心肌细胞中则受到抑制。LIF诱导的BNP mRNA表达上调在感染Adβ-gal和AdGab1WT的心肌细胞中出现，但在感染AdGab1F627/659的心肌细胞中未出现。相反，Gab1通过与SHP2相互作用抑制骨骼肌α-肌动蛋白mRNA的表达。此外，与感染Adβ-gal的心肌细胞相比，感染AdGab1WT的心肌细胞中细胞外信号调节激酶5（ERK5）的激活增强，但在感染AdGab1F627/659的心肌细胞中受到抑制。AdGab1WT与携带显性负性ERK5的腺病毒载体共感染可消除LIF诱导的心肌细胞纵向伸长。综上所述，这些发现表明Gab1-SHP2相互作用通过激活ERK5在gp130依赖性心肌细胞纵向伸长中起关键作用。
