Matsunaga H, Nishimoto I, Kojima I, Yamashita N, Kurokawa K, Ogata E
Fourth Department of Internal Medicine, University of Tokyo School of Medicine, Japan.
Am J Physiol. 1988 Oct;255(4 Pt 1):C442-6. doi: 10.1152/ajpcell.1988.255.4.C442.
Insulin-like growth factor II (IGF II) is a member of somatomedin family and is a potent mitogen in various types of mammalian cells. We have recently reported that IGF II stimulates calcium influx in competent BALB/c 3T3 cells primed with epidermal growth factor (J. Biol. Chem. 262: 12120-12126, 1987). Using patch-clamp technique, we show here an IGF II-sensitive cation channel in BALB/c 3T3 cell plasma membrane. Calcium is permeable to this cation channel and its opening behavior is independent of membrane potential. IGF II increases the opening probability of the identical channel in cells pretreated sequentially with platelet-derived growth factor and epidermal growth factor, whereas IGF II does not affect the opening of the channel in G0-arrested cells. This cation channel activity is observed only when IGF II is included in the patch pipette, indicating direct regulation of the channel by IGF II. We suggest that IGF II stimulates calcium influx by opening this cation channel and that IGF II activates the channel in a unique cell cycle-dependent manner.
胰岛素样生长因子II（IGF II）是生长调节素家族的一员，是各类哺乳动物细胞中一种强大的促有丝分裂原。我们最近报道，IGF II能刺激经表皮生长因子预处理的有能力的BALB/c 3T3细胞中的钙内流（《生物化学杂志》262: 12120 - 12126, 1987）。利用膜片钳技术，我们在此展示了BALB/c 3T3细胞质膜中一种对IGF II敏感的阳离子通道。钙可透过此阳离子通道，且其开放行为与膜电位无关。IGF II增加了先用血小板衍生生长因子再用表皮生长因子顺序预处理的细胞中同一通道的开放概率，而IGF II不影响处于G0期停滞的细胞中该通道的开放。只有当膜片吸管中含有IGF II时才能观察到这种阳离子通道活性，这表明IGF II对该通道有直接调节作用。我们认为IGF II通过打开此阳离子通道刺激钙内流，且IGF II以一种独特的细胞周期依赖性方式激活该通道。
