DISRUPTION OF MICROFILAMENT ORGANIZATION IN LIVING NONMUSCLE CELLS BY MICROINJECTION OF PLASMA VITAMIN-D-BINDING PROTEIN OR DNASE-I
DISRUPTION OF MICROFILAMENT ORGANIZATION IN LIVING NONMUSCLE CELLS BY MICROINJECTION OF PLASMA VITAMIN-D-BINDING PROTEIN OR DNASE-I
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DOI：
10.1073/pnas.87.14.5474
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发表时间：
1990-07-01
影响因子：
11.1
通讯作者：
SANGER, JW
中科院分区：
文献类型：
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作者：
SANGER, JM;DABIRI, G;SANGER, JW
血浆维生素D结合蛋白(DBP)与单体肌动蛋白结合，当它被显微注射到非肌肉细胞中时，会导致应激纤维的分解。应力纤维网络的破坏还伴随着细胞的形状变化，类似于细胞松弛素治疗后的变化。当DBP与荧光标记的α-肌动蛋白共注射时，30分钟后未见荧光应激纤维或附着斑块。12小时后，细胞恢复了扁平的形状和应力纤维。荧光标记的DBP引起与未标记的蛋白质相同的可逆的细胞形状变化。注射后，标记的DBP扩散到整个细胞质，在12小时内以点状模式定位，推测是由于溶体隔离。同样将DBP注射到骨骼肌管和心肌细胞中，不会导致新生和/或完全形成的肌原纤维的形状改变或分解，尽管DBP与肌肉肌动蛋白的结合亲和力是非肌肉异肌动蛋白的2倍。显微注射DNase I后，在非肌肉细胞中也观察到了类似的差异效应，DNase I是另一种能够结合单体肌动蛋白的蛋白质。这些显微注射的单体肌动蛋白结合蛋白的作用表明，需要一种可接近的池单体肌动蛋白来维持非肌肉细胞中应激纤维的完整性，而不是肌肉细胞中新生或完全形成的肌原纤维的完整性。
Plasma vitamin D-binding protein (DBP), which binds to monomeric actin, causes the breakdown of stress fibers when it is microinjected into nonmuscle cells. Disruption of the stress fiber network is also accompanied by shape changes in the cell that resemble those seen after cytochalasin treatment. When DBP was coinjected with fluorescently labeled .alpha.-actinin, no fluorescent stress fibers or attachment plaques were visible 30 min after injection. Twelve hours later the cells regained their flattened shape and their stress fibers. Fluorescently labeled DBP causes the same reversible changes in cell shape as the unlabeled protein. Upon injection, the labeled DBP diffuses throughout the cytoplasm, becoming localized by 12 hr in a punctate pattern, presumably due to lysozomal sequestration. Similar injections of DBP into skeletal myotubes and cardiac myocytes did not lead to shape changes or breakdown of nascent and/or fully formed myofibrils, even though DBP has a 2-fold higher binding affinity for muscle actin over that of the nonmuscle isoactins. Similar differential effects in nonmuscle cells were also observed after the microinjection of DNase I, another protein capable of binding monomer actin. The effects of these microinjected monomer actin-binding proteins imply that an accessible pool monomer actin is needed to maintain stress fiber integrity in nonmuscle cells but not the integrity of the nascent or fully formed myofibrils in muscle cells.