Semenova S B, Kiselev K I, Mozhaeva G N
Institute of Cytology, Russian Academy of Sciences, St. Petersburg.
Neurosci Behav Physiol. 1999 May-Jun;29(3):339-45. doi: 10.1007/BF02465347.
Local voltage clamping was applied to mouse macrophage plasma membrane to study calcium channels activated by inositol-1,4,5-triphosphate (IP3) and blocked by heparin. These channels were clearly distinguished from IP3-activated channels of the endoplasmic reticulum by their low conductivity (about 1 pSm for 100 mM Ca2+), high selectivity for Ca2+ relative to K+ (P(Ca):P(K) > 1000), calcium inactivation, and activation on hyperpolarization; these properties allowed them to be assigned to the I(CRAC) family. On the other hand, the properties of the IP3 receptors of these channels (IP3R), i.e., the dose-dependent effect of IP3, the IP3 desensitization of the receptor, and the sensitivity to micromolar concentrations of heparin and arachidonic acid were close to those of the endoplasmic reticulum IP3 receptor. The most likely interpretation of these data is that IP3R are not located in the endoplasmic reticulum, but, acting via some kind of conformational change occurring on binding of IP3, transmit a signal from the endoplasmic reticulum to the highly selective Ca2+ channels. This point of view is in agreement with the published "coupling model" [1].
将局部电压钳技术应用于小鼠巨噬细胞膜，以研究由肌醇-1,4,5-三磷酸（IP3）激活并被肝素阻断的钙通道。这些通道的电导率较低（对于100 mM Ca2+约为1 pS），相对于K+对Ca2+具有高选择性（P(Ca):P(K) > 1000），具有钙失活特性，且在超极化时激活，从而与内质网的IP3激活通道明显区分开来；这些特性使其被归为I(CRAC)家族。另一方面，这些通道的IP3受体（IP3R）的特性，即IP3的剂量依赖性效应、受体的IP3脱敏作用以及对微摩尔浓度肝素和花生四烯酸的敏感性，与内质网IP3受体的特性相近。对这些数据最合理的解释是，IP3R并非位于内质网中，而是通过IP3结合时发生的某种构象变化起作用，将信号从内质网传递至高度选择性的Ca2+通道。这一观点与已发表的“偶联模型”[1]一致。
