Level of expression of phospholipid scramblase regulates induced movement of phosphatidylserine to the cell surface
Level of expression of phospholipid scramblase regulates induced movement of phosphatidylserine to the cell surface
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DOI：
10.1074/jbc.273.12.6603
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发表时间：
1998-03-20
影响因子：
4.8
通讯作者：
Sims, PJ
中科院分区：
文献类型：
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作者：
Zhao, J;Zhou, QS;Sims, PJ
我们最近鉴定了一种 35 kDa 红细胞膜蛋白（磷脂扰乱酶），它可促进重组蛋白脂质体中磷脂酰丝氨酸 (PS) 和其他磷脂 (PL) 的 Ca2+ 依赖性跨双层运动（Zhou, Q.、Zhao, J.、Stout, J. G.、Luhm, R. A、Wiedmer, T. 和 Sims, P. J.， (1997) J. Biol Chen 272, 18240-18244)。为了确定在暴露于升高的胞质钙浓度 ([Ca2+](c)) 的其他细胞中，相同的蛋白质是否负责 PS 从内质膜小叶到外质膜小叶的快速移动，我们分析了如何诱导 PS 移动到细胞表面与 PL 扰乱酶的表达相关。暴露于 Ca2+ 离子载体 A28187 会导致 PL 扰乱酶组成性高的细胞系（HEL、Epstein-Barr 病毒转化的 B 淋巴细胞和 Jurkat）快速暴露于 PS，而在表达少量该蛋白的细胞（Raji、HL60 和 Dami）中，这种反应明显减弱。为了证实 PL 扰乱酶表达与 [Ca2+](c) 升高时 PS 排出之间的明显相关性，用 pEGFP-C2 中的 PL 扰乱酶 cDNA 转染 Raji 细胞，并获得表达不同量 GFP-PL 扰乱酶融合蛋白的稳定转化体。表达 GFP-PL 扰乱酶的克隆显示出明显的质膜定位荧光。与未转染的 Raji 细胞或单独表达 GFP 的转化体相比，表达 GFP-PL 扰乱酶融合蛋白的克隆显示出细胞表面 PS 暴露增加，以响应 [Ca2+](c) 升高，同时伴有凝血酶原酶复合物的膜催化功能表达增加。这些数据表明，用 PL 扰乱酶 cDNA 转染可促进 PS 向细胞表面的移动，并表明该蛋白通常介导质膜磷脂的重新分配在活化、损伤或凋亡的细胞中。
We recently identified a 35-kDa erythrocyte membrane protein, phospholipid scramblase, that promotes Ca2+-dependent transbilayer movement of phosphatidylserine (PS) and other phospholipids (PL) in reconstituted proteoliposomes (Zhou, Q., Zhao, J., Stout, J. G., Luhm, R. A, Wiedmer, T., and Sims, P. J, (1997) J. Biol. Chen 272, 18240-18244). To determine whether this same protein is responsible for the rapid movement of PS from inner-to-outer plasma membrane leaflets in other cells exposed to elevated cytosolic calcium concentration ([Ca2+](c)), we analyzed how induced movement of PS to the cell surface related to expression of PL scramblase. Exposure to Ca2+ ionophore A28187 resulted in rapid PS exposure in those cell lines constitutively high in PL scramblase (HEL, Epstein-Barr virus-transformed B-lymphocytes, and Jurkat), whereas this response was markedly attenuated in cells expressing low amounts of this protein (Raji, HL60, and Dami). To confirm this apparent correlation between PL scramblase expression and PS egress at elevated [Ca2+](c), Raji cells were transfected with PL scramblase cDNA in pEGFP-C2, and stable transformants expressing various amounts of GFP-PL scramblase fusion protein were obtained. Clones expressing GFP-PL scramblase showed distinctly plasma membrane-localized fluorescence. When compared either with untransfected Raji cells or with transformants expressing GFP alone, clones expressing GFP-PL scramblase fusion protein showed increased exposure of PS at the cell surface in response to elevated [Ca2+](c), accompanied by increased expression of membrane catalytic function for the prothrombinase enzyme complex, These data indicate that transfection with PL scramblase cDNA promotes movement of PS to cell surfaces and suggest that this protein normally mediates redistribution of plasma membrane phospholipids in activated, injured, or apoptotic cells.