Arispe N, Rojas E, Genge B R, Wu L N, Wuthier R E
Laboratory of Cell Biology and Genetics, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Biophys J. 1996 Oct;71(4):1764-75. doi: 10.1016/S0006-3495(96)79377-3.
Matrix vesicles (MVs), structures that accumulate Ca2+ during the initiation of mineral formation in growing bone, are rich in annexin V. When MVs are fused with planar phospholipid bilayers, a multiconductance Ca2+ channel is formed, with activity essentially identical to that observed when annexin V is delivered to the bilayer with phosphatidylserine liposomes. Ca2+ currents through this channel, from either MV or annexin V liposomes, are blocked by Zn2+, as is Ca2+ uptake by MV incubated in synthetic cartilage lymph. Blockage by Zn2+ was most effective when applied to the side containing the MV or liposomes. ATP and GTP differentially modulated the activity of this channel: ATP increased the amplitude of the current and the number of conductance states; GTP dramatically reduced the number of events and conductance states, leading to well-defined Ca2+ channel activity from either MV or the annexin V liposomes. In the distinctive effects of ATP, GTP, and Zn2+ on the Ca2+ channel activity observed in both the MV and the liposome systems, the common factor was the presence of annexin V. From this we conclude that Ca2+ entry into MV results from the presence of annexin V in these membrane-enclosed structures.
基质小泡（MVs）是在生长中的骨骼矿物质形成起始阶段积累Ca2+的结构，富含膜联蛋白V。当MVs与平面磷脂双层融合时，会形成一个多电导Ca2+通道，其活性与用磷脂酰丝氨酸脂质体将膜联蛋白V递送至双层时观察到的活性基本相同。通过该通道的Ca2+电流，无论是来自MV还是膜联蛋白V脂质体，都会被Zn2+阻断，在合成软骨淋巴中孵育的MV对Ca2+的摄取也是如此。当应用于含有MV或脂质体的一侧时，Zn2+的阻断最为有效。ATP和GTP对该通道的活性有不同的调节作用：ATP增加了电流幅度和电导状态的数量；GTP显著减少了事件和电导状态的数量，导致来自MV或膜联蛋白V脂质体的Ca2+通道活性明确。在MV和脂质体系统中观察到的ATP、GTP和Zn2+对Ca2+通道活性的独特影响中，共同因素是膜联蛋白V的存在。由此我们得出结论，Ca2+进入MV是由于这些膜封闭结构中存在膜联蛋白V。
