Linking reproductive behaviour and dense core granule biogenesis in secondary cells of the Drosophila male reproductive system

所有的动物都是由细胞组成的，每个细胞都有自己的功能，这些细胞一起工作，以确保基本的生物过程保持平衡。为了实现这一点，神经元和腺体内的许多不同细胞以一种受控的方式分泌信号。当正常的平衡被扰乱或当环境的变化需要身体相应地调整时，这些信号指示邻近或远处的细胞改变它们的行为。例如，当血糖水平升高时，胰腺中的β细胞会分泌更多的胰岛素，指示其他细胞吸收糖并恢复平衡，而肾上腺髓质中的神经样细胞则会释放肾上腺素，以应对压力，为我们的身体做好战斗或奔跑的准备。参与这种调节形式的分泌的细胞有共同的特征。他们将释放的荷尔蒙或酶包装到特殊的隔间，在那里分子在分泌之前被浓缩成所谓的致密核心颗粒(DCGS)。其中涉及的一些机制已经被详细描述，但其他方面却知之甚少。例如，细胞如何感觉到它们必须在颗粒释放后迅速补充它们的DCGS？这又如何与改变分泌率的环境信号相协调呢？虽然回答第一个问题依赖于开发测试基因如何控制形成DCGS的微小间隔的方法，但还必须在整个动物中研究这些间隔，以找出它们如何受到环境的影响。由于DCG控制机制在糖尿病和癌症等疾病中出现问题，在糖尿病和癌症中，肿瘤细胞向周围的正常细胞发出不适当的信号，了解分泌是如何调节的，有可能改变我们检测和治疗这些疾病的方式。我们正在通过研究成年果蝇雄性生殖系统中称为次级细胞(SCs)的特殊前列腺样细胞来研究这个问题。与老鼠等动物相比，研究苍蝇分泌背后的遗传学要容易得多，尽管苍蝇表面上很简单，但它与人类有惊人的相似之处。我们已经发现，干细胞有非常大的DCGs，其中一些在每次雄蝇交配时释放到精液中。控制人类DCG形成的机制似乎与干细胞中这些间隔的形成有关。但我们也发现，被称为BMPs的分子参与了DCG释放的感知，它指示SCs制造新的隔室，我们认为这种机制在哺乳动物中是保守的。此外，我们首次能够使用一种新型的超分辨率显微镜来观察活着的腺体中巨大的DCGS的形成，揭示了这一过程的其他新特征。我们现在建议研究BMP控制DCG形成的准确方式，以及交配过程中大脑活动如何增加BMP信号，从而产生更多的颗粒。此外，我们将测试我们发现的一些新的DCG控制机制的重要性，例如通过纳米级小泡将分子输送到DCGS，这些小泡也是由哺乳动物细胞制造的，但以前没有与DCG的形成有关。总体而言，我们拟议的研究将利用干细胞的独特生物学以及我们利用遗传学和交配苍蝇改变其分泌的能力来研究在活动物中控制不同方面分泌的方式。了解其中涉及的基本机制也可能有助于我们确定它们在其他分泌细胞中是如何出错的：例如，在2型糖尿病或癌症等疾病中，分泌缺陷会导致身体代谢控制系统的失衡，而在癌症中，分泌缺陷可以对正常细胞进行重新编程，以帮助肿瘤细胞存活。我们已经通过我们之前对苍蝇的研究建立了合作联系，以推进这项以疾病为主导的工作，因为我们对这个项目控制分泌的方式有了新的见解。

All animals are formed from cells, each with their own functions, which work together to ensure that basic biological processes are kept in balance. To achieve this, neurons and many different cells within glands secrete signals in a controlled way. These signals instruct neighbouring or distant cells to change their behaviour when the normal balance is disturbed or when changes in the environment require the body to adjust accordingly. For example, beta cells in the pancreas secrete more insulin when blood sugar levels are raised, instructing other cells to take up the sugar and restore equilibrium, while nerve-like cells in the adrenal medulla release adrenaline in response to stress to prepare our bodies to fight or run.Cells involved in this regulated form of secretion share common features. They package the hormones or enzymes they release into special compartments, where the molecules are condensed into so-called dense core granules (DCGs) before secretion. Some mechanisms involved have been characterised in detail, but other aspects are poorly understood. For example, how do cells sense that they must rapidly replenish their DCGs after granule release? And how can this be co-ordinated with signals from the environment that alter secretion rates? While answering the first question relies on developing ways of testing how genes control the tiny compartments in which DCGs are formed, these compartments must also be studied in the whole animal to work out how they are affected by the environment. Since DCG control mechanisms go wrong in diseases like diabetes, where insulin secretion is defective, and cancer, where tumour cells signal inappropriately to normal cells around them, understanding how secretion is regulated has the potential to change the way we detect and treat these diseases.We are investigating this problem by studying special prostate-like cells called secondary cells (SCs) in the male reproductive system of the adult fruit fly. It is much easier to study the genetics behind secretion in flies than in animals like mice, and despite the fly's apparent simplicity, it shares remarkable similarities with humans. We have found that SCs have very large DCGs, some of which are released into seminal fluid each time a male fly mates. Mechanisms that control DCG formation in humans seem to be involved in making these compartments in SCs. But we have also found that molecules called BMPs, which are involved in sensing DCG release, instruct SCs to make new compartments, a mechanism that we think is conserved in mammals. In addition, we have been able to use a new type of super-resolution microscopy to watch the giant DCGs form in living glands for the first time, revealing other new features of this process.We now propose to work out the precise way in which BMPs control DCG formation and how brain activity during mating increases the BMP signal so more granules are made. In addition, we will test the importance of some of the new mechanisms for DCG control we have uncovered, such as the delivery of molecules to DCGs on nano-sized vesicles, which are also made by mammalian cells, but have not previously been linked to DCG formation.Overall, our proposed studies will use the unique biology of SCs and our ability to change their secretion using genetics and by mating flies to work out the ways in which different aspects of secretion are controlled in a living animal. Understanding the basic mechanisms involved may also help us to determine how they go wrong in other secreting cells: for example, in diseases like Type 2 diabetes, where faulty secretion leads to imbalance in the body's metabolic control systems, or cancer, where defective secretion can reprogramme normal cells to help tumour cells survive. We have already established collaborative links through our previous studies in flies to take this disease-led work forward as we gain new insights into the ways secretion is controlled from this project.