肌节Z盘:心肌细胞的信号转导中心

近年发现，除形成Z盘的骨架蛋白外，还有许多蛋白定位于Z盘，如结合或募集离子通道、Na-Ca交换体、蛋白激酶、蛋白磷酸酶、磷酸二酯酶、蛋白水解酶、组蛋白乙酰转移酶与组蛋白脱乙酰化酶等的蛋白分子，参与了多条信号转导通道的信号调节作用。Z盘还能感知心肌细胞的应力与应变，使结合其上的一些蛋白向核转位，调节基因表达。另外，T管穿行于Z盘之间，可使各类调节信号能快速发挥作用。因此，Z盘部位实质上成为心肌细胞中的信号转导中心。

Sarcomeric Z-disc:A center of signaling transduction in cardiomyocytes

Sarcomere represents the fundamental contractile unit of cardiomyocytes.The lateral boundaries of a single sarcomere are built up by Z-discs,which also represent a key interface between the contractile apparatus and the cytoskeleton.Z-discs provide a backbone for the insertions of actin-based thin filaments as well as titin and nebulin/nebulette.Z-discs can also transmit forces generated within the sarcomere to the extracellular matrix.In addition to the cytoskeletal proteins,Z-discs are composed of a large number of adaptor proteins and other molecules.These proteins can bind or recruit ion channels,Na-Ca exchanger,protein kinases,protein phosphatases,phosphodiesterases,proteases,acetylases and deacetylases,which are involved in multiple signal transduction pathways.Z-discs also sense the stress and strain from sarcomeres and drive nuclear translocation of some shuttle proteins that modulate gene expression.Transverse tubules are invaginations of the surface membrane that form a complex network surrounding myofibrils.Therefore,the transverse tubule network is a structure that allows rapid propagation of excitation and biochemical signals into Z-discs.In summary,Z-discs are a bona fide center of signal transduction in cardiomyocytes.