A role for a novel animal endo-lysosomal Ca2+/H+ exchanger in Ca2+ signalling and chemotaxis.

钙可能是我们所有人都熟悉的一种矿物质，对健康的骨骼和牙齿很重要。但不太为人所知的是，它在我们的细胞中扮演着至关重要的角色，在细胞中，它控制着几乎所有生命必不可少的过程。钙的升高标志着生命的开始(在受精期间)，并在早期发育期间一次又一次地被利用(例如，在控制细胞在整个胚胎中迁移的方式)。这些上升驱动我们的神经冲动和我们的心跳。钙的变化是由一个微妙平衡的蛋白质网络来购买的，这些蛋白质在我们细胞内精确定义的时间和特定位置提供钙。因此，即使是钙水平的微小缺陷也可能导致疾病。因此，准确地了解细胞内钙是如何控制的，对于了解细胞是如何工作的至关重要--这是设计纠正疾病中错误的钙水平的方法的关键第一步。溶酶体是存在于细胞内的充满酸的小结构(细胞器)，传统上被认为是细胞的循环中心。但现在有许多证据来自对海胆卵的早期研究，表明它们和一些相关的结构是钙的重要来源。这些所谓的“酸性钙库”调节着许多细胞过程。此外，这些钙库对钙的处理有缺陷也是包括帕金森氏症在内的几种疾病的重要原因。我们实验室的工作已经帮助确定了哪些蛋白质可以使钙从这些存储中释放出来。但目前尚不清楚钙是如何被吸收的。这是我们知识中的一个重大空白，需要紧急填补。植物生物学家对钙如何被吸收到他们研究的细胞中的酸性钙储存有更好的理解。一种方式是通过一种被称为钙氢交换器(CAX)的蛋白质家族的作用。有很多证据表明，这些蛋白质也会填充动物体内的酸性钙存储，但编码它们的相应基因的鉴定还处于起步阶段。在我们最初的实验中，我们从海胆和青蛙--两种常用的实验动物--中鉴定了CAX基因。我们发现青蛙CAX定位于酸性钙库，并参与调节钙水平。我们还表明，对酸性细胞器的化学干扰会阻止胚胎细胞对一种激素样物质的正常迁移，这种物质已知会推动钙的变化。这些数据为了解CAX在动物中的分子身份和功能提供了新的见解。在这一应用中，我们汇集了一支在酸性钙储存、植物CAX和细胞迁移方面具有专业知识的科学家团队。我们将根据我们的初步发现来确定i)CAX在细胞内的准确位置，ii)CAX的钙“运输”活动的细节(包括CAX是否可以用来重置疾病细胞中有缺陷的钙水平)，以及iii)确定CAX在细胞迁移中的作用。这个项目的成功结果将为我们提供关于酸性钙储存如何处理钙的新信息，重要的是为我们提供进一步研究的新工具。它还将为这些存储在细胞迁移中的作用提供新的见解。这个过程对于正确的发展至关重要。团队的集体专业知识意味着我们可以应用广泛的技术来实现我们的目标。这也意味着我们获得的信息将对许多科学家有用，而不仅仅是我们各自领域的科学家。这些科学家包括：1)其他充满酸的细胞器(如激素储存库)中的钙；2)酸性细胞器完成的既定过程(如回收材料)；3)其他生物体(如植物和酵母)中与CAX相关的蛋白质；4)特定疾病(如癌症)。

Calcium is familiar to perhaps all of us as a mineral that is important for healthy bones and teeth. But less familiar is its vital role within our cells where it controls nearly all processes essential for life. Calcium rises signal the very start of life (during fertilization) and are used, time and time again, during early development (in for example controlling the way in which cells migrate throughout the embryo). These rises drive our nerve impulses and our heart beats. Calcium changes are bought about by a delicately balanced network of proteins which act to deliver calcium at precisely defined times and at specific locations within our cells. Thus, even subtle defects in calcium levels can precipitate disease. Understanding exactly how calcium is controlled within cells is thus vital for understanding how cells work - a critical first step towards devising ways to correct faulty calcium levels in disease.Lysosomes are small acid filled structures (organelles) present within our cells and which are traditionally thought of as the cell's recycling centre. But there is now much evidence stemming from early work in sea urchin eggs suggesting that they and a number of related structures are important sources of calcium. These so called "acidic calcium stores" regulate a number of cellular processes. Moreover, defective handling of calcium by these stores is also emerging as important in several diseases including Parkinson's disease. Work from our lab has helped to identify the proteins which open to allow calcium to be released from these stores. But how calcium is taken up is not known. This is a major gap in our knowledge that requires urgent filling.Plant biologists have a much better understanding of how calcium is taken up in to acidic calcium stores in the cells they study. One way is by the actions of a family of proteins known as calcium hydrogen exchangers (CAXs). There is much evidence to suggest that these proteins also fill acidic calcium stores in animals but identification of the corresponding genes which encode them is only in its infancy.In our initial experiments, we identified CAX genes from the sea urchin and frog - two commonly used laboratory animals. We showed that frog CAX localizes to acidic calcium stores and that it is involved in regulating calcium levels. We also showed that chemically interfering with acidic organelles prevents the normal migration of embryonic cells in response to a hormone-like substance which is known to drive changes in calcium. These data provide new insight in to the molecular identity and function of CAXs in animals.In this application, we bring together a team of scientists with expertise in the study of acidic calcium stores, CAXs in plants and migration of cells. We will build on our preliminary findings to determine i) the precise location of CAX within cells, ii) details of the calcium "transporting" activity of CAX (including whether CAX can be used to reset defective calcium levels in diseased cells) and iii) to define the role of CAX in cell migration.The successful outcome of this project will provide us with new information on how calcium is handled by acidic calcium stores and importantly provide us with new tools for further study. It will also provide new insight in to the role of these stores in migration of cells. This process is vital for proper development.The collective expertise of the team means that we can apply a broad range of techniques to achieve our aims. It also means that the information we obtain will be useful to a number of scientists and not only those in our respective fields. These scientists include those studying i) calcium in other acid-filled organelles (such as stores of hormones), ii) established processes that acidic organelles fulfil (such as recycling materials), iii) related CAX proteins in other organisms (such as plants and yeast) and iv) specific diseases (such as cancer).