Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
Biochem J. 2012 Sep 15;446(3):437-43. doi: 10.1042/BJ20120570.
Hsp20 (heat-shock protein of 20 kDa; HspB6) is a cardioprotective agent which combats a number of pathophysiological processes in the heart, including hypertrophy, apoptosis and ischaemia/reperfusion injury. The cardioprotective actions of Hsp20 require its phosphorylation by PKA (cAMP-dependent protein kinase) on Ser(16). Although the extracellular stimuli that promote cAMP-responsive phosphorylation of Hsp20 are well known, less is understood about the molecular processes that regulate this modification. AKAPs (A-kinase-anchoring proteins) physically compartmentalize PKA to specific locations within a cell to both direct PKA phosphorylation toward selected substrates and to orchestrate downstream signalling events. In the present study we used PKA anchoring disruptor peptides to verify that an AKAP underpins the cardioprotective phosphorylation of Hsp20. Biochemical and immunofluorescence techniques identify the cytosolic protein AKAP-Lbc (AKAP13) as the anchoring protein responsible for directing PKA phosphorylation of Hsp20 on Ser(16). Gene silencing and rescue experiments establish that AKAP-Lbc-mediated PKA phosphorylation of Hsp20 is crucial to the anti-apoptotic effects of the Hsp. Thus AKAP-Lbc may serve an ancillary cardioprotective role by favouring the association of PKA with Hsp20.
热休克蛋白 20（Hsp20，分子量为 20kDa；HspB6）是一种心脏保护剂，可对抗心脏中的多种病理生理过程，包括肥大、细胞凋亡和缺血/再灌注损伤。Hsp20 的心脏保护作用需要 PKA（cAMP 依赖性蛋白激酶）在 Ser16 对其进行磷酸化。虽然促进 Hsp20 的 cAMP 反应性磷酸化的细胞外刺激因素众所周知，但对于调节这种修饰的分子过程知之甚少。AKAP（A-激酶锚定蛋白）将 PKA 物理分隔到细胞内的特定位置，以将 PKA 磷酸化导向选定的底物，并协调下游信号事件。在本研究中，我们使用 PKA 锚定破坏肽来验证 AKAP 是支持 Hsp20 心脏保护性磷酸化的基础。生化和免疫荧光技术鉴定细胞质蛋白 AKAP-Lbc（AKAP13）为负责指导 Hsp20 在 Ser16 上的 PKA 磷酸化的锚定蛋白。基因沉默和挽救实验确定 AKAP-Lbc 介导的 Hsp20 的 PKA 磷酸化对于 Hsp 的抗细胞凋亡作用至关重要。因此，AKAP-Lbc 可以通过促进 PKA 与 Hsp20 的结合来发挥辅助心脏保护作用。
