Abstract：
Z-discs are core ultrastructural organizers of cardiomyocytes that modulate many facets of cardiac pathogenesis. Yet a comprehensive proteomic atlas of Z-disc-associated components remain incomplete. Here, we established an adeno-associated virus (AAV)-delivered, cardiomyocyte-specific, proximity-labeling approach to characterize the Z-disc proteome in vivo. We found palmdelphin (PALMD) as a novel Z-disc-associated protein in both adult murine cardiomyocytes and human pluripotent stem cell-derived cardiomyocytes. Germline and cardiomyocyte-specific Palmd knockout mice were grossly normal at baseline but exhibited compromised cardiac hypertrophy and aggravated cardiac injury upon long-term isoproterenol treatment. By contrast, cardiomyocyte-specific PALMD overexpression was sufficient to mitigate isoproterenol-induced cardiac injury. PALMD ablation perturbed the transverse tubule (T-tubule)-sarcoplasmic reticulum (SR) ultrastructures, which formed the Z-disc-associated junctional membrane complex (JMC) essential for calcium handling and cardiac function. These phenotypes were associated with the reduction of nexilin (NEXN), a crucial Z-disc-associated protein that is essential for both Z-disc and JMC structures and functions. PALMD interacted with NEXN and enhanced its protein stability while the Nexn mRNA level was not affected. AAV-based NEXN addback rescued the exacerbated cardiac injury in isoproterenol-treated PALMD-depleted mice. Together, this study discovered PALMD as a potential target for myocardial protection and highlighted in vivo proximity proteomics as a powerful approach to nominate novel players regulating cardiac pathogenesis.
摘要：
Z-盘是调节心脏发病机制的许多方面的心肌细胞的核心超微结构组织者。然而，Z盘相关成分的全面蛋白质组学图谱仍然不完整。这里,我们建立了一种腺相关病毒（AAV），心肌细胞特异性，邻近标记方法在体内表征Z盘蛋白质组。我们发现palmdelphin（PALMD）在成年鼠心肌细胞和人类多能干细胞衍生的心肌细胞中都是一种新型的Z盘相关蛋白。胚系和心肌细胞特异性Palmd敲除小鼠在基线时大致正常，但在长期异丙肾上腺素治疗后表现出受损的心脏肥大和加重的心脏损伤。相比之下,心肌细胞特异性PALMD过表达足以减轻异丙肾上腺素诱导的心脏损伤。PALMD消融扰乱了横管（T管）-肌浆网（SR）超微结构，形成了钙处理和心脏功能所必需的Z-盘相关连接膜复合物（JMC）。这些表型与nexilin（NEXN）的减少有关，一种关键的Z-盘相关蛋白，对Z-盘和JMC的结构和功能都至关重要。PALMD与NEXN相互作用并增强其蛋白质稳定性，而NexnmRNA水平不受影响。基于AAV的NEXN回补挽救了异丙肾上腺素治疗的PALMD耗竭小鼠中加剧的心脏损伤。一起,这项研究发现PALMD是心肌保护的潜在靶标,并强调体内邻近蛋白质组学是提名调节心脏发病机制的新参与者的有力方法.
