Wang Zheng, Linden Lara M, Naegeli Kaleb M, Ziel Joshua W, Chi Qiuyi, Hagedorn Elliott J, Savage Natasha S, Sherwood David R
Department of Biology, Duke University, Durham, NC 27708.
Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, England, UK.
J Cell Biol. 2014 Sep 1;206(5):619-33. doi: 10.1083/jcb.201405026. Epub 2014 Aug 25.
The receptor deleted in colorectal cancer (DCC) directs dynamic polarizing activities in animals toward its extracellular ligand netrin. How DCC polarizes toward netrin is poorly understood. By performing live-cell imaging of the DCC orthologue UNC-40 during anchor cell invasion in Caenorhabditis elegans, we have found that UNC-40 clusters, recruits F-actin effectors, and generates F-actin in the absence of UNC-6 (netrin). Time-lapse analyses revealed that UNC-40 clusters assemble, disassemble, and reform at periodic intervals in different regions of the cell membrane. This oscillatory behavior indicates that UNC-40 clusters through a mechanism involving interlinked positive (formation) and negative (disassembly) feedback. We show that endogenous UNC-6 and ectopically provided UNC-6 orient and stabilize UNC-40 clustering. Furthermore, the UNC-40-binding protein MADD-2 (a TRIM family protein) promotes ligand-independent clustering and robust UNC-40 polarization toward UNC-6. Together, our data suggest that UNC-6 (netrin) directs polarized responses by stabilizing UNC-40 clustering. We propose that ligand-independent UNC-40 clustering provides a robust and adaptable mechanism to polarize toward netrin.
在结直肠癌中缺失的受体（DCC）引导动物体内的动态极化活动朝向其细胞外配体网蛋白。DCC如何向网蛋白极化尚不清楚。通过对线虫锚定细胞侵入过程中DCC同源物UNC-40进行活细胞成像，我们发现UNC-40聚集、招募F-肌动蛋白效应器，并在没有UNC-6（网蛋白）的情况下产生F-肌动蛋白。延时分析显示，UNC-40聚集体在细胞膜的不同区域以周期性间隔组装、拆卸和重新形成。这种振荡行为表明UNC-40通过一种涉及相互关联的正反馈（形成）和负反馈（拆卸）的机制聚集。我们表明内源性UNC-6和异位提供的UNC-6定向并稳定UNC-40聚集。此外，UNC-40结合蛋白MADD-2（一种TRIM家族蛋白）促进不依赖配体的聚集和UNC-40向UNC-6的强大极化。总之，我们的数据表明UNC-6（网蛋白）通过稳定UNC-40聚集来引导极化反应。我们提出不依赖配体的UNC-40聚集提供了一种强大且适应性强的机制来向网蛋白极化。
