Nager Andrew R, Goldstein Jaclyn S, Herranz-Pérez Vicente, Portran Didier, Ye Fan, Garcia-Verdugo Jose Manuel, Nachury Maxence V
Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5345, USA.
Laboratorio de Neurobiología Comparada, Instituto Cavanilles, Universitat de València, CIBERNED, 46980 Valencia, Spain; Unidad Mixta de Esclerosis Múltiple y Neurorregeneración, IIS Hospital La Fe-UVEG, 46026 Valencia, Spain.
Cell. 2017 Jan 12;168(1-2):252-263.e14. doi: 10.1016/j.cell.2016.11.036. Epub 2016 Dec 22.
Signaling receptors dynamically exit cilia upon activation of signaling pathways such as Hedgehog. Here, we find that when activated G protein-coupled receptors (GPCRs) fail to undergo BBSome-mediated retrieval from cilia back into the cell, these GPCRs concentrate into membranous buds at the tips of cilia before release into extracellular vesicles named ectosomes. Unexpectedly, actin and the actin regulators drebrin and myosin 6 mediate ectosome release from the tip of cilia. Mirroring signal-dependent retrieval, signal-dependent ectocytosis is a selective and effective process that removes activated signaling molecules from cilia. Congruently, ectocytosis compensates for BBSome defects as ectocytic removal of GPR161, a negative regulator of Hedgehog signaling, permits the appropriate transduction of Hedgehog signals in Bbs mutants. Finally, ciliary receptors that lack retrieval determinants such as the anorexigenic GPCR NPY2R undergo signal-dependent ectocytosis in wild-type cells. Our data show that signal-dependent ectocytosis regulates ciliary signaling in physiological and pathological contexts.
信号受体在诸如Hedgehog等信号通路激活后会动态地从纤毛中退出。在此,我们发现,当激活的G蛋白偶联受体(GPCR)未能通过BBSome介导从纤毛中回收并回到细胞内时,这些GPCR会在纤毛尖端聚集形成膜性芽,然后释放到名为外泌体的细胞外囊泡中。出乎意料的是,肌动蛋白以及肌动蛋白调节因子脑桥蛋白和肌球蛋白6介导外泌体从纤毛尖端释放。与信号依赖的回收过程类似,信号依赖的胞吐作用是一个选择性且有效的过程,可从纤毛中去除激活的信号分子。同样,胞吐作用可弥补BBSome缺陷,因为通过胞吐作用去除Hedgehog信号的负调节因子GPR161,可使Bbs突变体中Hedgehog信号得以适当转导。最后,缺乏回收决定因素的纤毛受体,如厌食性GPCR NPY2R,在野生型细胞中会发生信号依赖的胞吐作用。我们的数据表明,信号依赖的胞吐作用在生理和病理情况下调节纤毛信号传导。