Dou Jian-Ping, Jiao Bo, Sheng Juan-Juan, Yu Zhi-Bin
Key Laboratory of Aerospace Medicine, Ministry of Education; Department of Aerospace Physiology, Fourth Military Medical University, Xi'an 710032, China.
Sheng Li Xue Bao. 2014 Oct 25;66(5):569-74.
The intercalated disc (ICD) complex of cardiomyocyte consists of fascia adherens, desmosomes and gap junctions which are mainly constructed by their transmembrane proteins: N-cadherin (N-cad), desmoglein-2 (DSG2) and connexin 43 (Cx43), respectively. The aim of this study was to observe the dynamic changes in colocalization of N-cad, DSG2 and Cx43 with each other in the rat left ventricular myocardium at 1, 7, 14, 28 and 90 day(s) after birth (P1, P7, P14, P28 and P90) using immunofluorescent staining. The results showed that, N-cad, DSG2 and Cx43 located all around the plasma membrane at the P1. These proteins accumulated to the long ends of cardiomyocytes, indicating preliminary formation of the ICD at the P7. The localization of three proteins at the ICD increased progressively, but their lateral localization showed an inverse trend from the P14 to P90. However, Cx43 still kept a certain amount of lateral localization in cardiomyocytes even at the P90 as compared with N-cad and DSG2. Quantitative colocalization of proteins was analyzed by the stereological method. Total percentage of colocalization of N-cad with DSG2 was 33.5% at the P1, and increased to 38.6% at the P7, 9.4% in ICD and 29.2% in lateral side. The total percentage of colocalization of N-cad with DSG2 increased to 65.7% at the P90, ICD colocalization increasing to 60.5% and lateral colocalization decreasing to 5.2%. Total percentage of colocalization of N-cad with Cx43 increased from 10.3% at the P1 to 37.1% at the P90, and only ICD colocalization increased, but lateral colocalization kept about 5%. The colocalization pattern of DSG2 with Cx43 was similar to that of N-cad with Cx43. Total percentage of colocalization of N-cad with DSG2 was higher than those of N-cad or DSG2 with Cx43. The above results suggest that the formation of mechanical junctions at the ICD of cardiomyocyte is prior to that of electrochemistry junctions during postnatal development. In other words, cardiomyocyte growth needs a stable mechanical environment at first.
心肌细胞的闰盘（ICD）复合体由黏合带、桥粒和缝隙连接组成，这些结构主要分别由其跨膜蛋白构建而成：N-钙黏蛋白（N-cad）、桥粒芯糖蛋白-2（DSG2）和连接蛋白43（Cx43）。本研究的目的是利用免疫荧光染色观察出生后1、7、14、28和90天（P1、P7、P14、P28和P90）大鼠左心室心肌中N-cad、DSG2和Cx43相互之间共定位的动态变化。结果显示，在P1时，N-cad、DSG2和Cx43位于质膜周围。这些蛋白在心肌细胞的长轴末端聚集，表明在P7时ICD初步形成。从P14到P90，这三种蛋白在ICD处的定位逐渐增加，但其侧向定位呈现相反趋势。然而，与N-cad和DSG2相比，即使在P90时，Cx43在心肌细胞中仍保持一定量的侧向定位。采用体视学方法分析蛋白的定量共定位。N-cad与DSG2的共定位总百分比在P1时为33.5%，在P7时增加到38.6%，在ICD处为9.4%，在侧面为29.2%。N-cad与DSG2的共定位总百分比在P90时增加到65.7%，ICD处共定位增加到60.5%，侧面共定位减少到5.2%。N-cad与Cx43的共定位总百分比从P1时的10.3%增加到P90时的37.1%，仅ICD处共定位增加，而侧面共定位保持在约5%。DSG2与Cx43的共定位模式与N-cad与Cx43的相似。N-cad与DSG2的共定位总百分比高于N-cad或DSG2与Cx43的共定位总百分比。上述结果表明，在出生后发育过程中，心肌细胞ICD处机械连接的形成先于电化学连接的形成。换句话说，心肌细胞生长首先需要一个稳定的机械环境。
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