Goncharova E J, Kam Z, Geiger B
Department of Cell Cultures, Academy of Sciences of the USSR, Leningrad.
Development. 1992 Jan;114(1):173-83. doi: 10.1242/dev.114.1.173.
The distribution of adherens junction (AJ) components was investigated in cultured heart myocytes. These cells, derived from either newborn rats or chick embryos, develop elaborate arrays of myofibrils which become extensive and laterally aligned following several days in culture. The Z-disks in these cells, visualized by immunolabeling with antibodies to muscle-specific alpha-actinin, exhibit a characteristic periodicity of about 2 microns and are in register with those of neighboring myofibrils throughout the sarcoplasm. Vinculin, in these cells, associates with intercellular AJ and cell-matrix adhesions. In addition, this protein is detected in periodic bands located along the lateral cell membranes corresponding to "costamers" previously described by Pardo, J.V., Siliciano, J.D. and Craig, S.W. (Proc. Natn. Acad. Sci. USA, 80, 1008). Similarly, N-cadherin, which is predominantly associated with intercellular junctions, is also detected in periodic striations located mainly on the dorsal and lateral cell surfaces. Using computer-aided three-dimensional microscopy confirmed that these vinculin- and N-cadherin-containing structures are located in extrajunctional sites, apparently associated with Z-disks of peripheral myofibrils. Based on these findings an alternative pathway is proposed for the assembly of vinculin and N-cadherin, which is not triggered by adhesive interactions with extracellular surfaces but rather by interactions at the membrane-cytoplasm interphase with the periphery of the pre-assembled myofibrils. Moreover, we present evidence that antibodies to N-cadherin, which are capable of blocking AJ formation in culture, have an inhibitory effect also on the development and alignment of myofibrils. We discuss the functional significance of the "costameric" organization of vinculin and N-cadherin and consider its involvement both in the lateral alignment of neighboring muscle cells and in the stabilization of developing myofibrils.
在培养的心肌细胞中研究了黏着连接（AJ）成分的分布。这些细胞来源于新生大鼠或鸡胚，培养几天后会形成复杂的肌原纤维阵列，这些肌原纤维会变得广泛且横向排列。通过用肌肉特异性α-肌动蛋白抗体进行免疫标记可视化的这些细胞中的Z盘，呈现出约2微米的特征性周期性，并且在整个肌浆中与相邻肌原纤维的Z盘对齐。在这些细胞中，纽蛋白与细胞间AJ和细胞-基质黏附相关。此外，在沿着对应于先前由帕尔多、J.V.、西利西亚诺、J.D.和克雷格、S.W.（《美国国家科学院院刊》，80，1008）描述的“肌联蛋白”的外侧细胞膜的周期性条带中检测到这种蛋白质。同样，主要与细胞间连接相关的N-钙黏着蛋白也在主要位于细胞背侧和外侧表面的周期性条纹中被检测到。使用计算机辅助三维显微镜证实，这些含有纽蛋白和N-钙黏着蛋白的结构位于连接外位点，显然与外周肌原纤维的Z盘相关。基于这些发现，提出了一种纽蛋白和N-钙黏着蛋白组装的替代途径，该途径不是由与细胞外表面的黏附相互作用触发，而是由在膜-细胞质界面与预组装肌原纤维外周的相互作用触发。此外，我们提供证据表明，能够在培养中阻断AJ形成的N-钙黏着蛋白抗体对肌原纤维的发育和排列也有抑制作用。我们讨论了纽蛋白和N-钙黏着蛋白“肌联蛋白”组织的功能意义，并考虑其在相邻肌肉细胞横向排列和发育中肌原纤维稳定中的作用。
