Ludwig-Peitsch Wiebke K
Department of Dermatology, Vivantes Klinikum im Friedrichshain, Landsberger Allee 49, 10249, Berlin, Germany.
Adv Exp Med Biol. 2017;1006:329-336. doi: 10.1007/978-4-431-56550-5_19.
Drebrin E contributes to remodeling of the actin cytoskeleton and formation of cell processes. Therefore, its role in cell migration was studied in prototypes of motile cells with prominent lamellipodia such as murine B16F1 melanoma and Swiss 3T3 cells and in human SV80 fibroblasts. Confocal microscopy revealed absence of drebrin from the tips of lamellipodia but enrichment in the tail of the cells, in retraction zones and in a specific juxtanuclear actin filament compartment, named "drebrin-enriched zone." A similar subset of juxtanuclear actin filaments is characterized by the actin-binding protein SWAP-70, but drebrin and SWAP-70 localized to different compartments, suggesting the existence of novel distinct subdomains within the actin filament system. In cells overexpressing drebrin-EGFP, numerous long, branched cell processes were formed which slowly retracted and extended. However, in stable transfectants containing lower amounts of the fusion protein, drebrin-EGFP was recruited to the same sites as the endogenous protein during cell migration, i.e., to retracting membrane domains and into the juxtanuclear drebrin-enriched zone. In the leading edges of SV80 cells, characterized by pronounced actin microspikes, drebrin was concentrated along posterior portions of the microspikes, together with tropomyosin, with which it competes for actin binding. Drebrin knockdown by siRNA did not impact forward migration or ruffling. Taken together, these findings suggest that during cell migration drebrin is involved in retraction processes but not in lamellipodia formation. The novel, sizable juxtanuclear drebrin-enriched zone remains to be characterized in detail with respect to its molecular assembly and functions.
drebrin E有助于肌动蛋白细胞骨架的重塑和细胞突起的形成。因此，在具有明显片状伪足的运动细胞原型中，如小鼠B16F1黑色素瘤细胞和瑞士3T3细胞以及人SV80成纤维细胞中，研究了其在细胞迁移中的作用。共聚焦显微镜显示，片状伪足尖端没有drebrin，但在细胞尾部、收缩区和一个特定的近核肌动蛋白丝区室（称为“drebrin富集区”）中富集。近核肌动蛋白丝的一个类似亚群以肌动蛋白结合蛋白SWAP-70为特征，但drebrin和SWAP-70定位于不同的区室，这表明在肌动蛋白丝系统中存在新的不同亚域。在过表达drebrin-EGFP的细胞中，形成了许多长的、分支的细胞突起，这些突起缓慢收缩和伸展。然而，在含有较低量融合蛋白的稳定转染子中，在细胞迁移过程中，drebrin-EGFP被募集到与内源性蛋白相同的位点，即收缩膜结构域和近核drebrin富集区。在以明显的肌动蛋白微刺为特征的SV80细胞前缘，drebrin与原肌球蛋白一起集中在微刺的后部，它与原肌球蛋白竞争肌动蛋白结合。通过siRNA敲低drebrin不影响细胞向前迁移或波动。综上所述，这些发现表明，在细胞迁移过程中，drebrin参与收缩过程，但不参与片状伪足的形成。关于其分子组装和功能，这个新的、相当大的近核drebrin富集区仍有待详细表征。
