Hayashi M, Saito Y, Kawashima S
Department of Biochemistry, Tokyo Metropolitan Institute of Gerontology, Japan.
Biochem Biophys Res Commun. 1992 Jan 31;182(2):939-46. doi: 10.1016/0006-291x(92)91822-8.
The membrane mobility agent, 2-(methoxyethoxy)ethyl-cis-8-(2-octylcyclopropyl)octanoate (A2C) promotes the fusion of rat, rabbit, and human erythrocytes in the presence of exogenous Ca2+. Under these conditions, the high sensitivity form of calcium-activated neutral protease (mu-calpain) in erythrocytes is activated autolytically. mu-Calpain is activated in accordance with fusion; that is, both erythrocyte fusion and autolytic activation of mu-calpain are induced in rat erythrocytes at 30 min, in rabbit erythrocytes at 150 min, and in human erythrocytes at 240 min after the addition of A2C and Ca2+. When erythrocytes are preincubated with the Ca2+ ionophore A23187, both fusion and autolytic activation start earlier. A leupeptin analogue, Cbz-Leu-Leu-Leu-aldehyde (ZLLLal), inhibits both the autolytic activation of mu-calpain and fusion induced by A2C and Ca2+. These results indicate that treatment of erythrocytes with A2C and Ca2+, results in first an influx of Ca2+ into the cells, followed by autolytic activation of mu-calpain, proteolysis of membrane proteins, exposure of fusion-sites, and, finally, fusion of erythrocytes.
膜流动性促进剂2-(甲氧基乙氧基)乙基-顺式-8-(2-辛基环丙基)辛酸酯(A2C)在存在外源Ca2+的情况下可促进大鼠、兔和人红细胞的融合。在这些条件下，红细胞中钙激活中性蛋白酶的高敏感性形式(μ-钙蛋白酶)会发生自溶激活。μ-钙蛋白酶的激活与融合同步；也就是说，在添加A2C和Ca2+后，大鼠红细胞在30分钟时、兔红细胞在150分钟时、人红细胞在240分钟时均会诱导红细胞融合和μ-钙蛋白酶的自溶激活。当红细胞与Ca2+离子载体A23187预孵育时，融合和自溶激活均会提前开始。一种亮抑酶肽类似物，苄氧羰基-亮氨酰-亮氨酰-亮氨醛(ZLLLal)可抑制A2C和Ca2+诱导的μ-钙蛋白酶自溶激活和融合。这些结果表明，用A2C和Ca2+处理红细胞，首先会导致Ca2+流入细胞，随后是μ-钙蛋白酶的自溶激活、膜蛋白的蛋白水解、融合位点的暴露，最终是红细胞的融合。
