Franzini-Armstrong C
Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia 19104-6058, USA.
FASEB J. 1999 Dec;13 Suppl 2:S266-70. doi: 10.1096/fasebj.13.9002.s266.
Activation of muscle contraction is a rapid event that is initiated by electrical activity in the surface membrane and transverse (T) tubules. This is followed by release of calcium from the inner membrane system, the sarcoplasmic reticulum (SR). Using electron microscopy (EM), K. R. Porter and his laboratory defined the SR, the unique junctions between SR and T tubules, and the continuity between T tubules and surface membrane. Current research in this area centers on the interaction between T tubules and SR. This is mediated by 2 well-identified calcium channels: the dihydropyridine receptors (DHPRs) that act as voltage sensors in the T tubules, and the ryanodine receptors (RyRs) or calcium release channels of the SR. The relative positions of these 2 molecules differ significantly in skeletal and cardiac muscle, and this correlates well with known functional differences in the control of contraction. Molecular biology experiments combined with EM indicate that DHPRs are linked to RyRs in skeletal but probably not in cardiac muscle.
肌肉收缩的激活是一个快速事件，由表面膜和横（T）小管中的电活动引发。随后是钙离子从内膜系统即肌浆网（SR）的释放。利用电子显微镜（EM），K. R. 波特及其实验室确定了肌浆网、肌浆网与T小管之间独特的连接以及T小管与表面膜之间的连续性。该领域目前的研究集中在T小管与肌浆网之间的相互作用。这是由两种已明确的钙通道介导的：作为T小管电压传感器的二氢吡啶受体（DHPRs），以及肌浆网的兰尼碱受体（RyRs）或钙释放通道。这两种分子在骨骼肌和心肌中的相对位置差异显著，这与收缩控制中已知的功能差异密切相关。结合电子显微镜的分子生物学实验表明，在骨骼肌中DHPRs与RyRs相连，但在心肌中可能并非如此。
