Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Yamadaoka, Osaka, Japan.
J Mol Cell Cardiol. 2010 Aug;49(2):157-64. doi: 10.1016/j.yjmcc.2010.03.001. Epub 2010 Mar 11.
Morphological and biochemical phenotypes of cardiomyocyte hypertrophy are determined by neurohumoral factors. Stimulation of G protein-coupled receptor (GPCR) results in uniform cell enlargement in all directions with an increase in skeletal alpha-actin (alpha-SKA) gene expression, while stimulation of gp130 receptor by interleukin-6 (IL-6)-related cytokines induces longitudinal elongation with no increase in alpha-SKA gene expression. Thus, alpha-SKA is a discriminating marker for hypertrophic phenotypes; however, regulatory mechanisms of alpha-SKA gene expression remain unknown. Here, we clarified the role of SH2-containing protein tyrosine phosphatase 2 (SHP2) in alpha-SKA gene expression. In neonatal rat cardiomyocytes, endothelin-1 (ET-1), a GPCR agonist, but not leukemia inhibitory factor (LIF), an IL-6-related cytokine, induced RhoA activation and promotes alpha-SKA gene expression via RhoA. In contrast, LIF, but not ET-1, induced activation of SHP2 in cardiomyocytes, suggesting that SHP2 might negatively regulate alpha-SKA gene expression downstream of gp130. Therefore, we examined the effect of adenovirus-mediated overexpression of wild-type SHP2 (SHP2(WT)), dominant-negative SHP2 (SHP2(C/S)), or beta-galactosidase (beta-gal), on alpha-SKA gene expression. LIF did not upregulate alpha-SKA mRNA in cardiomyocytes overexpressing either beta-gal or SHP2(WT). In cardiomyocytes overexpressing SHP2(C/S), LIF induced upregulation of alpha-SKA mRNA, which was abrogated by concomitant overexpression of either C3-toxin or dominant-negative RhoA. RhoA was activated after LIF stimulation in the cardiomyocytes overexpressing SHP2(C/S), but not in myocytes overexpressing beta-gal. Furthermore, SHP2 mediates LIF-induced longitudinal elongation of cardiomyocytes via ERK5 activation. Collectively, these findings indicate that SHP2 negatively regulates alpha-SKA expression via RhoA inactivation and suggest that SHP2 implicates ERK5 in cardiomyocyte elongation downstream of gp130.
心肌细胞肥大的形态和生化表型由神经激素因素决定。G 蛋白偶联受体（GPCR）的刺激导致所有方向的均匀细胞增大，伴有骨骼α-肌动蛋白（α-SKA）基因表达增加，而白细胞介素-6（IL-6）相关细胞因子刺激 gp130 受体诱导纵向伸长，α-SKA 基因表达没有增加。因此，α-SKA 是肥大表型的鉴别标志物；然而，α-SKA 基因表达的调节机制尚不清楚。在这里，我们阐明了含 SH2 的蛋白酪氨酸磷酸酶 2（SHP2）在α-SKA 基因表达中的作用。在新生大鼠心肌细胞中，内皮素-1（ET-1），一种 GPCR 激动剂，但不是白血病抑制因子（LIF），一种 IL-6 相关细胞因子，诱导 RhoA 激活，并通过 RhoA 促进α-SKA 基因表达。相反，LIF，但不是 ET-1，诱导心肌细胞中 SHP2 的激活，表明 SHP2 可能在 gp130 下游负调节α-SKA 基因表达。因此，我们检查了腺病毒介导的野生型 SHP2（SHP2(WT)）、显性失活 SHP2（SHP2(C/S)）或β-半乳糖苷酶（β-gal）过表达对α-SKA 基因表达的影响。LIF 未上调过表达β-gal 或 SHP2(WT)的心肌细胞中的α-SKA mRNA。在过表达 SHP2(C/S)的心肌细胞中，LIF 诱导α-SKA mRNA 的上调，同时过表达 C3 毒素或显性失活 RhoA 可阻断该上调。在过表达 SHP2(C/S)的心肌细胞中，LIF 刺激后 RhoA 被激活，但在过表达β-gal 的肌细胞中没有被激活。此外，SHP2 通过 ERK5 激活介导 LIF 诱导的心肌细胞纵向伸长。总之，这些发现表明 SHP2 通过 RhoA 失活负调节α-SKA 表达，并表明 SHP2 在 gp130 下游涉及 ERK5 在心肌细胞伸长中的作用。
