A new intracellular foctor for regulation of Ca channel.

电压操纵型L钙通道在细胞兴奋中起重要作用，与节律性放电、突触传递、肌肉收缩和分泌有关。然而，钙通道的衰败一直是研究该通道的障碍。我们一直在研究与理解通道活动调节有关的衰竭机制。我们以前已经提出，细胞质因素参与了通道活性的维持，而这些因素的洗脱是衰竭的原因。细胞质中一种可能的因子的性质类似于钙调蛋白，一种钙激活的中性蛋白酶的内源性抑制物。然而，分离的细胞质或纯化的钙调蛋白显示出有限的恢复通道活性的能力。这暗示可能存在其他辅助因素(S)。因此，本研究旨在阐明细胞质因子的性质。研究发现，另一种蛋白样因子与钙调蛋白和三磷酸腺苷一起，可恢复L型钙通道的活动。

Voltage-operated L-type Ca^<2+> channels play important roles in cellular excitation related to rhythmic firing, synaptic transmission, muscle contraction and secretion. However, run-down of the Ca^<2+> channel has been an obstacle to studies of the channel. We have been investigating the mechanism of run-down in relation to the understanding of the regulation of channel activity. We have suggested previously that cytoplasmic factors are involved in maintenance of channel activity, and that wash-out of the factors is the cause of run-down. The properties of one possible factor in cytoplasm resemble those of calpastatin, an endogenous inhibitor of Ca-activated neutral protease. However, fractionated cytoplasm or purified calpastatin shows a limited ability to recover channel activity. This implied that there might be other co-factor(s). Therefore, this study was carried out to elucidate the nature of the cytoplasmic factors. It was found that another protein-like factor, together with calpastatin and ATP, restores L-type Ca^<2+> channel activity.