The Felsenstein Medical Research Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
PLoS One. 2013 Sep 16;8(9):e71100. doi: 10.1371/journal.pone.0071100. eCollection 2013.
Popeye domain containing1 (Popdc1), also named Bves, is an evolutionary conserved membrane protein. Despite its high expression level in the heart little is known about its membrane localization and cardiac functions. The study examined the hypothesis that Popdc1 might be associated with the caveolae and play a role in myocardial ischemia tolerance. To address these issues, we analyzed hearts and cardiomyocytes of wild type and Popdc1-null mice. Immunoconfocal microscopy revealed co-localization of Popdc1 with caveolin3 in the sarcolemma, intercalated discs and T-tubules and with costameric vinculin. Popdc1 was co-immunoprecipitated with caveolin3 from cardiomyocytes and from transfected COS7 cells and was co-sedimented with caveolin3 in equilibrium density gradients. Caveolae disruption by methyl-β-cyclodextrin or by ischemia/reperfusion (I/R) abolished the cellular co-localization of Popdc1 with caveolin3 and modified their density co-sedimentation. The caveolin3-rich fractions of Popdc1-null hearts redistributed to fractions of lower buoyant density. Electron microscopy showed a statistically significant 70% reduction in caveolae number and a 12% increase in the average diameter of the remaining caveolae in the mutant hearts. In accordance with these changes, Popdc1-null cardiomyocytes displayed impaired [Ca(+2)]i transients, increased vulnerability to oxidative stress and no pharmacologic preconditioning. In addition, induction of I/R injury to Langendorff-perfused hearts indicated a significantly lower functional recovery in the mutant compared with wild type hearts while their infarct size was larger. No improvement in functional recovery was observed in Popdc1-null hearts following ischemic preconditioning. The results indicate that Popdc1 is a caveolae-associated protein important for the preservation of caveolae structural and functional integrity and for heart protection.
菠菜域包含 1 型（Popdc1），也称为 Bves，是一种进化上保守的膜蛋白。尽管它在心内的表达水平很高，但对其膜定位和心脏功能知之甚少。本研究检验了 Popdc1 可能与 caveolae 相关并在心肌缺血耐受中发挥作用的假说。为了解决这些问题，我们分析了野生型和 Popdc1 基因敲除小鼠的心脏和心肌细胞。免疫共聚焦显微镜显示 Popdc1 与 caveolin3 在肌膜、闰盘和 T 小管以及与质膜斑蛋白 vinculin 共定位。Popdc1 可从心肌细胞和转染的 COS7 细胞中与 caveolin3 共免疫沉淀，并与 caveolin3 在平衡密度梯度中共同沉淀。甲基-β-环糊精或缺血/再灌注（I/R）破坏 caveolae 后，Popdc1 与 caveolin3 的细胞共定位消失，并改变了它们的密度共沉淀。Popdc1 基因敲除鼠心脏的 caveolin3 丰富部分重新分配到较低浮力密度的部分。电子显微镜显示，突变鼠心脏 caveolae 的数量统计学上显著减少了 70%，而剩余 caveolae 的平均直径增加了 12%。与这些变化一致，Popdc1 基因敲除的心肌细胞显示 [Ca(+2)]i 瞬变受损，对氧化应激的易感性增加，且无药物预处理。此外，Langendorff 灌注心脏的 I/R 损伤诱导表明，与野生型心脏相比，突变鼠心脏的功能恢复明显较低，而其梗死面积较大。在 Popdc1 基因敲除鼠心脏中，缺血预处理后未见功能恢复的改善。结果表明，Popdc1 是一种与 caveolae 相关的蛋白，对 caveolae 结构和功能完整性的保存以及心脏保护至关重要。
