Small heat-shock protein Hsp20 phosphorylation inhibits β-agonist-induced cardiac apoptosis
Small heat-shock protein Hsp20 phosphorylation inhibits β-agonist-induced cardiac apoptosis
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DOI：
10.1161/01.res.0000129179.66631.00
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发表时间：
2004-06-11
影响因子：
20.1
通讯作者：
Kranias, EG
中科院分区：
文献类型：
--
作者：
Fan, GC;Chu, GX;Kranias, EG
交感神经系统的激活是心力衰竭的常见代偿特征，但持续的β-肾上腺素能激活诱导心肌细胞死亡，导致心脏重塑和功能障碍。在小鼠心肌细胞中，我们最近报道，长期暴露于β-受体激动剂与短暂增加的表达和磷酸化的小热休克蛋白，热休克蛋白20。为了确定热休克蛋白20的功能意义，我们过表达这种蛋白质和其组成性磷酸化（S16 D）或非磷酸化（S16 A）的突变体在成年大鼠心肌细胞。热休克蛋白20保护心肌细胞免于cAMP-PKA通路激活引发的凋亡，如核固缩、末端脱氧核苷酸转移酶介导的dUTP缺口末端标记和DNA梯状化的数量减少所示，这些都与caspase-3活性的抑制有关。组成性磷酸化的Hsp 20突变体（S16 D）进一步增加了这些保护作用，这赋予了完全保护细胞凋亡。与此相反，nonphosphorylatable突变体（S16 A）没有表现出抗凋亡的特性。免疫染色研究和免疫沉淀与热休克蛋白20或肌动蛋白抗体表明，热休克蛋白20易位到细胞骨架和相关的肌动蛋白对异丙肾上腺素刺激。这些发现表明，热休克蛋白20和它的磷酸化Ser 16可能提供心脏保护β-激动剂诱导的细胞凋亡。因此，热休克蛋白20可能代表一个新的治疗靶点在治疗心力衰竭。
Activation of the sympathetic nervous system is a common compensatory feature in heart failure, but sustained beta-adrenergic activation induces cardiomyocyte death, leading to cardiac remodeling and dysfunction. In mouse cardiomyocytes, we recently reported that prolonged exposure to beta-agonists is associated with transient increases in expression and phosphorylation of a small heat-shock protein, Hsp20. To determine the functional significance of Hsp20, we overexpressed this protein and its constitutively phosphorylated (S16D) or nonphosphorylated (S16A) mutant in adult rat cardiomyocytes. Hsp20 protected cardiomyocytes from apoptosis triggered by activation of the cAMP-PKA pathway, as indicated by decreases in the number of pyknotic nuclei, terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling, and DNA laddering, which were associated with inhibition of caspase-3 activity. These protective effects were further increased by the constitutively phosphorylated Hsp20 mutant (S16D), which conferred full protection from apoptosis. In contrast, the nonphosphorylatable mutant ( S16A) exhibited no antiapoptotic properties. Immunostaining studies and immunoprecipitations with Hsp20 or actin antibodies demonstrated that Hsp20 translocated to cytoskeleton and associated with actin on isoproterenol stimulation. These findings suggest that Hsp20 and its phosphorylation at Ser16 may provide cardioprotection against beta-agonist-induced apoptosis. Thus, Hsp20 may represent a novel therapeutic target in the treatment of heart failure.