Mozhayeva G N, Naumov A P
Institute of Cytology, Academy of Sciences of the U.S.S.R., Leningrad.
J Membr Biol. 1991 Nov;124(2):113-26. doi: 10.1007/BF01870456.
Patch-clamp methods were used to search for and characterize channels that mediate calcium influx through the plasma membrane of human carcinoma A431 cells. Here we present four Ca(2+)-permeable channel types referred to as SG, G, 1 and BI. With 105 mM Ca2+ as the charge carrier, at 30-33 degrees C their mean unitary conductances (in pS) are: 1.3 (SG), 2.4 (G), 3.7 (I) and 12.8 (BI). SG and G channels are activated by nonhydrolyzable analogues of guanosine 5-triphosphate (GTP) applied to the inside of the membrane, suggesting an involvement of G-proteins in the control of their activity. I and BI channels are activated by inositol 1,4,5-trisphosphate (InsP3). G, I, BI and possibly SG channels are activated from the extracellular side of the membrane by epidermal growth factor (EGF) and histamine. It is assumed that all identified Ca2+ channels take part in the generation of the agonist-induced intracellular Ca2+ signal. The variety of Ca-channel types seems to be necessary to tune cell responses according to the respective type and level of an external signal, on the one hand, and to the functional state of the cell, on the other.
采用膜片钳技术来寻找并鉴定介导钙离子通过人源A431癌细胞质膜内流的通道。在此，我们展示了四种钙通透通道类型，分别称为SG、G、1和BI。以105 mM Ca2+作为载流子，在30 - 33摄氏度时，它们的平均单位电导（以pS计）分别为：1.3（SG）、2.4（G）、3.7（I）和12.8（BI）。SG和G通道可被施加于膜内侧的鸟苷5 - 三磷酸（GTP）的非水解类似物激活提示G蛋白参与调控其活性。I和BI通道可被肌醇1,4,5 - 三磷酸（InsP3）激活。G、I、BI以及可能的SG通道可被表皮生长因子（EGF）和组胺从膜的胞外侧激活。据推测，所有已鉴定的钙通道均参与激动剂诱导的细胞内钙信号的产生。一方面，多种钙通道类型对于根据外部信号的各自类型和水平以及另一方面根据细胞的功能状态来调节细胞反应似乎是必要的。
