Windoffer Reinhard, Kölsch Anne, Wöll Stefan, Leube Rudolf E
Department of Anatomy and Cell Biology, Johannes Gutenberg University, 55128 Mainz, Germany.
J Cell Biol. 2006 May 8;173(3):341-8. doi: 10.1083/jcb.200511124.
Recent studies showed that keratin filament (KF) formation originates primarily from sites close to the actin-rich cell cortex. To further characterize these sites, we performed multicolor fluorescence imaging of living cells and found drastically increased KF assembly in regions of elevated actin turnover, i.e., in lamellipodia. Abundant KF precursors (KFPs) appeared within these areas at the distal tips of actin stress fibers, moving alongside the stress fibers until their integration into the peripheral KF network. The earliest KFPs were detected next to actin-anchoring focal adhesions (FAs) and were only seen after the establishment of FAs in emerging lamellipodia. Tight spatiotemporal coupling of FAs and KFP formation were not restricted to epithelial cells, but also occurred in nonepithelial cells and cells producing mutant keratins. Finally, interference with FA formation by talin short hairpin RNA led to KFP depletion. Collectively, our results support a major regulatory function of FAs for KF assembly, thereby providing the basis for coordinated shaping of the entire cytoskeleton during cell relocation and rearrangement.
最近的研究表明，角蛋白丝（KF）的形成主要起源于富含肌动蛋白的细胞皮层附近的位点。为了进一步表征这些位点，我们对活细胞进行了多色荧光成像，发现在肌动蛋白周转增加的区域，即片状伪足中，KF组装急剧增加。大量的KF前体（KFP）出现在这些区域的肌动蛋白应力纤维的远端，沿着应力纤维移动，直到它们整合到外周KF网络中。最早的KFP在肌动蛋白锚定的粘着斑（FA）旁边被检测到，并且仅在新兴片状伪足中FA建立后才可见。FA和KFP形成的紧密时空耦合不仅限于上皮细胞，也发生在非上皮细胞和产生突变角蛋白的细胞中。最后，通过抑制踝蛋白的短发夹RNA干扰FA形成导致KFP减少。总体而言，我们的结果支持FA对KF组装的主要调节功能，从而为细胞迁移和重排过程中整个细胞骨架的协调塑造提供了基础。
