Membrane-based signalling pathways controlling sperm capacitation and fertility

为了使卵子受精，哺乳动物精子中的分子必须在与卵子相遇之前进行重组。这种重组是由精子收到的信号开始的，这些信号导致精子改变其细胞膜，并启动特定的内部反应，使其能够与卵子结合并穿透卵子。信号的确切性质(S)以及它们是如何接收的尚不清楚，这使得提高男性的生育力或保存用于人工授精的精子变得困难。其中一个分子，Na/K-ATPase，是众所周知的一种酶，可以将离子移动到许多细胞类型的膜上，最近在一些身体细胞中被认为是膜结合的信号受体。我们发现，它在精子中也有这种作用，就像膜受体对特定激素的存在所做的反应一样。在其他细胞上刺激它的激素是类固醇分子哇巴因。Na/K-ATPase由亚基组成，每个亚基都有几种亚型。把一个子单元想象成一台计算机，有台式机、笔记本电脑或iPad的同构，每种都需要略有不同的方法来打开它们。另一个子单元是外围设备，可以是打印机、扫描仪或网络摄像头。将任何一个计算机亚型与任何一个外周亚型配对会影响配对设备的功能，当然也会改变其输出。同样，精子Na/K-ATPase的异构体和亚基影响它的功能(作为酶或受体)，以及它是否可以运输离子或启动细胞内信号。我们建议确定特定的亚基，当配对在一起时，是一个活跃的信号受体。我们将确定这些亚基的特定氨基酸结构。由于哇巴因和黄体酮都是女性受精时存在的类固醇，我们将确定它们是否以及如何相互作用来控制Na/K-ATPase的作用。我们还将确定ATPase周围的其他膜分子如何影响其功能(您的计算机是在办公室还是在飞机上？)这些知识将帮助我们保护、预测和改善家养和濒危物种的ATPase功能和精子生育能力，并有可能在人类繁殖过程中发挥作用。

The molecules in mammalian sperm must reorganise just prior to meeting the egg, in order to fertilise it. This reorganisation is started by signals that the sperm receives which cause the sperm to change its membrane and start specific internal reactions that enable it to bind to and penetrate the egg. The exact nature of the signal(s), and how they are received, is unknown, making it difficult to improve the fertility of the male, or to preserve sperm for artificial insemination. One molecule, Na/K-ATPase, is well known as an enzyme that moves ions across the membranes of many cell types, and recently has been recognised as a membrane-bound signal receptor in some body cells. We showed that it also acts this way in the sperm, reacting as a membrane receptor does to the presence of a specific hormone. The hormone which stimulates it on other cells is the steroid molecule ouabain. Na/K-ATPase is made of subunits, each of which has several isoforms. Think of the one subunit as a computer, with isoforms of desktop, laptop or ipad, each requiring somewhat different methods to turn them on. The other subunit is a peripheral device, either a printer, scanner or webcam. Pairing any one computer isoform with any one peripheral isoform affects the function of the paired devices, and certainly changes its output. Similarly, isoforms and subunits in sperm Na/K-ATPase affect how it functions (as an enzyme or receptor), and whether it can transport ions or start an intracellular signal. We propose to identify the specific subunits that, when paired together, are an active signal-receptor. We will determine the specific amino acid structure of those subunits. Since both ouabain and progesterone are steroids present in the female at fertilization, we will determine if and how they interact to control Na/K-ATPase actions. We will also determine how other membrane molecules surrounding ATPase affect its function (is your computer in an office or airplane?). This knowledge will help us to protect, predict and improve ATPase function and sperm fertility for domestic and endangered species, and potentially in human reproduction.