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

钙是一种对骨骼和牙齿健康很重要的矿物质，我们可能都很熟悉。但人们不太熟悉的是它在我们细胞中的重要作用，它控制着几乎所有生命必需的过程。钙的升高标志着生命的开始（受精期间），并且在早期发育（例如控制细胞在胚胎中迁移的方式）中被一次又一次地使用。这些上升驱动着我们的神经冲动和心跳。钙的变化是由一个微妙平衡的蛋白质网络引起的，它在精确的时间和细胞内的特定位置传递钙。因此，即使是钙水平的细微缺陷也会引发疾病。因此，准确地了解细胞内钙是如何控制的对于理解细胞如何工作至关重要——这是设计出纠正疾病中钙水平错误的方法的关键的第一步。溶酶体是存在于我们细胞内的小的充满酸的结构（细胞器），传统上被认为是细胞的循环中心。但现在有很多证据表明，早期对海胆卵的研究表明，海胆卵和一些相关结构是钙的重要来源。这些所谓的“酸性钙储存”调节着许多细胞过程。此外，这些储存对钙的处理缺陷在包括帕金森病在内的几种疾病中也越来越重要。我们实验室的工作帮助我们确定了打开通道让钙从这些储存中释放出来的蛋白质。但是钙是如何被吸收的还不清楚。这是我们知识上的一大空白，急需填补。植物生物学家对他们所研究的细胞中钙是如何被吸收到酸性钙储存中的有了更好的了解。一种方法是通过被称为钙氢交换剂（CAXs）的蛋白质家族的作用。有很多证据表明，这些蛋白质也填补了动物体内的酸性钙储备，但对编码它们的相应基因的识别还处于起步阶段。在最初的实验中，我们从海胆和青蛙这两种常用的实验动物身上鉴定出了CAX基因。我们发现青蛙的CAX定位于酸性钙储存，并参与调节钙水平。我们还表明，化学干扰酸性细胞器会阻止胚胎细胞响应激素样物质的正常迁移，而激素样物质已知会驱动钙的变化。这些数据为动物体内cax的分子特性和功能提供了新的认识。在这个应用程序中，我们汇集了一个科学家团队，他们在研究酸性钙储存，植物中的cax和细胞迁移方面具有专业知识。我们将以我们的初步发现为基础，确定i) CAX在细胞内的精确位置，ii) CAX钙“运输”活性的细节（包括CAX是否可用于重置患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。该项目的成功结果将为我们提供关于钙如何被酸性钙储存处理的新信息，重要的是为我们进一步研究提供了新的工具。它还将为这些储存在细胞迁移中的作用提供新的见解。这一进程对适当发展至关重要。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。这些科学家包括研究i)其他充满酸的细胞器中的钙（如激素储存），ii)酸性细胞器完成的既定过程（如回收材料），iii)其他生物体（如植物和酵母）中的相关CAX蛋白以及iv)特定疾病（如癌症）的科学家。

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).