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NrCAM与细胞骨架的耦合取决于多个蛋白质结构域以及在脂筏中的分区。

NrCAM coupling to the cytoskeleton depends on multiple protein domains and partitioning into lipid rafts.

作者信息

Falk Julien, Thoumine Olivier, Dequidt Caroline, Choquet Daniel, Faivre-Sarrailh Catherine

机构信息

Neurogenèse et Morphogenèse du Développement à l'Adulte, UMR 6156 CNRS, Institut de Biologie du Développement de Marseille, Marseille, France.

出版信息

Mol Biol Cell. 2004 Oct;15(10):4695-709. doi: 10.1091/mbc.e04-03-0171. Epub 2004 Jul 14.

Abstract

NrCAM is a cell adhesion molecule of the L1 family that is implicated in the control of axonal growth. Adhesive contacts may promote advance of the growth cone by triggering the coupling of membrane receptors with the F-actin retrograde flow. We sought to understand the mechanisms leading to clutching the F-actin at the site of ligand-mediated clustering of NrCAM. Using optical tweezers and single particle tracking of beads coated with the ligand TAG-1, we analyzed the mobility of NrCAM-deletion mutants transfected in a neuroblastoma cell line. Deletion of the cytoplasmic tail did not prevent the coupling of NrCAM to the actin flow. An additional deletion of the FNIII domains to remove cis-interactions, was necessary to abolish the rearward movement of TAG-1 beads, which instead switched to a stationary behavior. Next, we showed that the actin-dependent retrograde movement of NrCAM required partitioning into lipid rafts as indicated by cholesterol depletion experiments using methyl-beta-cyclodextrin. Recruitment of the raft component caveolin-1 was induced at the adhesive contact between the cell surface and TAG-1 beads, indicating that enlarged rafts were generated. Photobleaching experiments showed that the lateral mobility of NrCAM increased with raft dispersion in these contact areas, further suggesting that TAG-1-coated beads induced the coalescence of lipid rafts. In conclusion, we propose that anchoring of NrCAM with the retrograde actin flow can be triggered by adhesive contacts via cooperative processes including interactions with the cytoplasmic tail, formation of cis-complex via the FNIII repeats, and lipid raft aggregation.

摘要

NrCAM是L1家族的一种细胞粘附分子,与轴突生长的控制有关。粘附接触可能通过触发膜受体与F-肌动蛋白逆行流的偶联来促进生长锥的前进。我们试图了解在NrCAM配体介导的聚集位点导致F-肌动蛋白紧握的机制。使用光镊和对包被有配体TAG-1的珠子进行单粒子追踪,我们分析了转染到神经母细胞瘤细胞系中的NrCAM缺失突变体的迁移率。细胞质尾巴的缺失并不妨碍NrCAM与肌动蛋白流的偶联。额外缺失FNIII结构域以消除顺式相互作用,对于消除TAG-1珠子的向后移动是必要的,此时TAG-1珠子会转变为静止行为。接下来,我们表明,如使用甲基-β-环糊精进行的胆固醇耗竭实验所示,NrCAM的肌动蛋白依赖性逆行移动需要分配到脂筏中。在细胞表面与TAG-1珠子之间的粘附接触处诱导了脂筏成分小窝蛋白-1的募集,表明产生了扩大的脂筏。光漂白实验表明,在这些接触区域中,NrCAM的横向迁移率随着脂筏的分散而增加,进一步表明包被有TAG-1的珠子诱导了脂筏的聚集。总之,我们提出,NrCAM与逆行肌动蛋白流的锚定可以通过粘附接触经由协同过程触发,这些过程包括与细胞质尾巴的相互作用、通过FNIII重复序列形成顺式复合物以及脂筏聚集。

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