It is widely assumed that synthesis of membrane proteins, particularly in the heart, follows the classical secretory pathway with mRNA translation occurring in perinuclear regions followed by protein trafficking to sites of deployment. However, this view is based on studies conducted in less-specialized cells, and has not been experimentally addressed in cardiac myocytes. Therefore, we undertook direct experimental investigation of protein synthesis in cardiac tissue and isolated myocytes using single-molecule visualization techniques and a novel proximity-ligated in situ hybridization approach for visualizing ribosome-associated mRNA molecules for a specific protein species, indicative of translation sites. We identify here, for the first time, that the molecular machinery for membrane protein synthesis occurs throughout the cardiac myocyte, and enables distributed synthesis of membrane proteins within sub-cellular niches where the synthesized protein functions using local mRNA pools trafficked, in part, by microtubules. We also observed cell-wide distribution of membrane protein mRNA in myocardial tissue from both non-failing and hypertrophied (failing) human hearts, demonstrating an evolutionarily conserved distributed mechanism from mouse to human. Our results identify previously unanticipated aspects of local control of cardiac myocyte biology and highlight local protein synthesis in cardiac myocytes as an important potential determinant of the heart’s biology in health and disease.

人们普遍认为，膜蛋白的合成，特别是在心脏中，遵循经典的分泌途径，mRNA 翻译发生在核周区域，然后蛋白质运输到部署部位。然而，这种观点是基于在特化程度较低的细胞中进行的研究，尚未在心肌细胞中进行实验研究。因此，我们使用单分子可视化技术和新的邻近连接原位杂交方法对心脏组织和分离的肌细胞中的蛋白质合成进行了直接实验研究，用于可视化特定蛋白质种类的核糖体相关 mRNA 分子，指示翻译位点。我们在这里首次发现膜蛋白合成的分子机制发生在整个心肌细胞中，并且能够在亚细胞生态位内实现膜蛋白的分布式合成，其中合成的蛋白质使用局部 mRNA 池发挥作用，部分通过微管运输。我们还观察到来自非衰竭和肥大（衰竭）人类心脏的心肌组织中膜蛋白 mRNA 的细胞范围分布，证明了从小鼠到人类的进化上保守的分布机制。我们的研究结果确定了心肌细胞生物学局部控制以前未预料到的方面，并强调心肌细胞中的局部蛋白质合成是心脏生物学在健康和疾病中的重要潜在决定因素。我们还观察到来自非衰竭和肥大（衰竭）人类心脏的心肌组织中膜蛋白 mRNA 的细胞范围分布，证明了从小鼠到人类的进化上保守的分布机制。我们的研究结果确定了心肌细胞生物学局部控制以前未预料到的方面，并强调心肌细胞中的局部蛋白质合成是心脏生物学在健康和疾病中的重要潜在决定因素。我们还观察到来自非衰竭和肥大（衰竭）人类心脏的心肌组织中膜蛋白 mRNA 的细胞范围分布，证明了从小鼠到人类的进化上保守的分布机制。我们的研究结果确定了心肌细胞生物学局部控制以前未预料到的方面，并强调心肌细胞中的局部蛋白质合成是心脏生物学在健康和疾病中的重要潜在决定因素。