The role of ciliary Ca2+ signalling in the regulation of intraflagellar transport

纤毛 Ca2 信号传导在鞭毛内运输调节中的作用

• 批准号: BB/M02508X/1
• 负责人: Glen Wheeler
• 金额: $ 53.11万
• 依托单位: Marine Biological Association of the United Kingdom
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2015
• 资助国家: 英国
• 起止时间: 2015 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FM02508X%2F1
• 关键词: role; ciliary; Ca2+; signalling; regulation

Cilia and flagella are tiny-hair-like projections from cells that play important roles in motility and in sensing changes in the cellular environment. Whilst we are familiar with their role in motility, the mechanisms cilia use to sense environmental stimuli and transmit this information to the rest of the cell are less clear.Cilia are built at the tip using a process known as intraflagellar transport (IFT), which enables proteins to be moved along the cilium to the site of assembly. It has also been shown that IFT plays an important role in ciliary signalling, as many important receptor proteins localise to cilia and are moved into and out of the cilium by IFT. Disruption of ciliary signalling due to defects in IFT can lead to human diseases and developmental problems, and it is therefore important for us to understand how intraflagellar transport is regulated.Using the motile green alga, Chlamydomonas, as a model system to study ciliary signalling, we recently discovered that IFT may be regulated by calcium signalling. Many environmental stimuli trigger ion channel proteins in cell membranes to open and cause a rapid influx of calcium ions (Ca2+) into cells. This results in elevated Ca2+ within the cell, which triggers various signalling cascades depending on the nature of the stimulus. Ca2+-dependent signalling processes are central to both the motile and sensory roles of cilia, but we know very little about the nature of these Ca2+ elevations and how they act to regulate ciliary processes. The discovery that Ca2+ signals are regulating IFT therefore links two very important processes in cilia and should help us understand much more about how these organelles sense and respond to their environment.We have used Chlamydomonas to develop a novel microscopy technique that allows us to simultaneously image Ca2+ and the movement of IFT particles in flagella for the first time. Chlamydomonas is currently the only organism in which this technique is possible and this unique ability will allow us to directly examine the mechanisms underlying this novel signalling process.Chlamydomonas can glide along solid substrates on its flagella by using IFT to move proteins in the flagella membrane. Gliding is coordinated by flagella Ca2+ signalling. Ca2+ elevations in one flagellum cause the IFT particles to dissociate from the flagella membrane and stop pulling the cell along. This gliding process is therefore an excellent model system in which to study how Ca2+ signalling regulates IFT to control the movement of flagella membrane proteins.Although we know that Ca2+ regulates IFT, we don't yet know how this happens. This proposal seeks to identify the specific cellular mechanisms responsible. Firstly, we will examine how Ca2+ signals are generated in Chlamydomonas flagella, looking at the ion channels responsible and at mechanisms that restrict Ca2+ elevations to individual flagella, to enable specific control of IFT during the regulation of gliding motility. We will then examine the different types of Ca2+ elevations that are used to regulate IFT, using mathematical models in combination with experimental data to help us understand the rapid changes in Ca2+ concentration inside the flagellum. Finally, we will look at how Ca2+ actually causes the IFT particles to dissociate from the flagella membrane, by identifying specific flagella proteins that may bind to Ca2+ and disrupt this interaction.The process of IFT is highly conserved amongst eukaryotes and it is likely that Ca2+-dependent regulation of IFT influences the movement of many ciliary proteins, including those involved in developmental signalling pathways relating to human genetic diseases. Therefore the results from our studies in algae will provide insight into how ciliary signalling is regulated in many different organisms, including mammals, and shed light on the many different roles cilia play in sensing and responding to the cellular environment.

纤毛和鞭毛是细胞中微小的毛发状突起，在运动和感知细胞环境的变化方面发挥着重要作用。虽然我们熟悉纤毛在运动中的作用，但纤毛用于感知环境刺激并将信息传递到细胞其余部分的机制不太清楚。纤毛是通过一种称为鞭毛内运输(IFT)的过程在顶端建造的，这种过程使蛋白质能够沿着纤毛移动到组装位置。研究还表明，IFT在纤毛信号传递中起着重要作用，因为许多重要的受体蛋白定位于纤毛，并被IFT移入和移出纤毛。由于IFT的缺陷导致纤毛信号的中断，从而导致人类疾病和发育问题，因此了解鞭毛内运输是如何被调控的是很重要的。我们使用移动的绿藻衣藻作为研究纤毛信号的模型系统，我们最近发现IFT可能受钙信号的调节。许多环境刺激触发细胞膜上的离子通道蛋白开放，导致钙离子(Ca~(2+))快速进入细胞内。这会导致细胞内钙离子升高，从而根据刺激的性质触发各种信号级联反应。依赖于钙离子的信号传递过程是纤毛运动和感觉作用的中心，但我们对这些钙离子升高的性质以及它们如何调节纤毛过程知之甚少。因此，钙离子信号调节IFT的发现将纤毛中两个非常重要的过程联系在一起，应该有助于我们更多地了解这些细胞器如何感知和响应环境。我们首次使用衣藻开发了一种新的显微镜技术，使我们能够同时成像钙离子和鞭毛中IFT颗粒的运动。衣藻是目前唯一能够实现这一技术的生物，这种独特的能力将使我们能够直接研究这一新的信号传递过程背后的机制。衣藻可以通过使用IFT移动鞭毛膜中的蛋白质来沿着鞭毛上的固体基质滑动。滑行是由鞭毛的钙信号来协调的。一个鞭毛中的钙离子升高会导致IFT颗粒从鞭毛膜上解离，并停止拉动细胞。因此，这个滑动过程是一个很好的模型系统，可以用来研究钙信号如何调节IFT来控制鞭毛膜蛋白的运动。虽然我们知道钙调节IFT，但我们还不知道这是如何发生的。这项建议试图确定具体的细胞机制负责。首先，我们将研究衣藻鞭毛中的钙信号是如何产生的，看看负责的离子通道和限制单个鞭毛的钙升高的机制，以便在滑动运动调节过程中对IFT进行特定的控制。然后，我们将研究用于调节IFT的不同类型的钙升高，使用数学模型结合实验数据来帮助我们了解鞭毛内钙浓度的快速变化。最后，我们将通过识别可能与Ca~(2+)结合并破坏这种相互作用的特定鞭毛蛋白，看看Ca~(2+)实际上如何导致IFT颗粒从鞭毛膜上解离。IFT的过程在真核生物中高度保守，很可能对IFT的钙依赖调节影响许多纤毛蛋白的运动，包括那些参与与人类遗传疾病相关的发育信号通路的蛋白。因此，我们对藻类的研究结果将为我们深入了解包括哺乳动物在内的许多不同生物体中纤毛信号是如何调节的，并阐明纤毛在感知和响应细胞环境方面扮演的许多不同角色。

项目成果

Insights into the red algae and eukaryotic evolution from the genome of Porphyra umbilicalis (Bangiophyceae, Rhodophyta)

• DOI: 10.1073/pnas.1703088114
• 发表时间: 2017-08-01
• 期刊: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• 影响因子: 11.1
• 作者: Brawley, Susan H.;Blouin, Nicolas A.;Prochnik, Simon E.
• 通讯作者: Prochnik, Simon E.