Takekura Hiroaki, Franzini-Armstrong Clara
Department of Physiological Sciences, National Institute of Fitness and Sports, Kanoya, Kagoshima 891-23, Japan.
Biophys J. 2002 Nov;83(5):2742-53. doi: 10.1016/S0006-3495(02)75284-3.
The relative disposition of ryanodine receptors (RyRs) and L-type Ca(2+) channels was examined in body muscles from three arthropods. In all muscles the disposition of ryanodine receptors in the junctional gap between apposed SR and T tubule elements is highly ordered. By contrast, the junctional membrane of the T tubule is occupied by distinctive large particles that are clustered within the small junctional domain, but show no order in their arrangement. We propose that the large particles of the junctional T tubules represent L-type Ca(2+) channels involved in excitation-contraction (e-c) coupling, based on their similarity in size and location with the L-type Ca(2+) channels or dihydropyridine receptors (DHPRs) of skeletal and cardiac muscle. The random arrangement of DHPRs in arthropod body muscles indicates that there is no close link between them and RyRs. This matches the architecture of vertebrate cardiac muscle and is in keeping with the similarity in e-c coupling mechanisms in cardiac and invertebrate striated muscles.
在三种节肢动物的体肌中，研究了兰尼碱受体（RyRs）和L型Ca(2+)通道的相对分布情况。在所有肌肉中，兰尼碱受体在相对的肌浆网（SR）和横小管（T小管）元件之间的连接间隙中的分布高度有序。相比之下，T小管的连接膜被独特的大颗粒占据，这些大颗粒聚集在小的连接区域内，但排列没有规律。基于它们在大小和位置上与骨骼肌和心肌的L型Ca(2+)通道或二氢吡啶受体（DHPRs）的相似性，我们认为T小管连接部位的大颗粒代表参与兴奋-收缩（e-c）偶联的L型Ca(2+)通道。节肢动物体肌中DHPRs的随机排列表明它们与RyRs之间没有紧密联系。这与脊椎动物心肌的结构相匹配，并且与心脏和无脊椎动物横纹肌中e-c偶联机制的相似性相符。
