Defining novel transport mechanisms for volume-regulating corticosteroids in the collecting duct of the kidney

皮质类固醇是关键的体积调节激素，其靶向肾脏的集合管，在那里它们迅速改变Na+和H2O转运，这一过程支持全身Na+平衡的微调并维持我们的循环体积。在生理条件下，盐皮质激素醛固酮由于酶11HSD2的活性而在集合管中特异性地起作用，所述酶11HSD2将更丰富的糖皮质激素皮质醇转化为无活性代谢物。然而，在某些条件下，糖皮质激素也可以刺激Na+转运。关于这些激素结合的类固醇受体，随后的转录事件及其对离子转运的影响，我们知道得很多。然而，很少有人知道这些激素的运动超出其亲脂性，赋予他们的能力，自由地扩散穿过质膜。曼斯利实验室已经产生了转录组学的配置文件映射的遗传信号支持皮质类固醇诱导的Na+运输的细胞模型的集合管。这项工作确定了几个家庭的膜转运蛋白的表达调节急性治疗皮质类固醇。初步研究表明，皮质类固醇可能实际上是积极运输的定向方式，激素的不对称分布的任何一侧的单层和可忽略不计的细胞内浓度。虽然在本领域中关于皮质类固醇特别是在集合管中的主动转运的描述很少，但其他研究组已经表明皮质类固醇可以主动转运到身体的其他地方，例如脑和脂肪组织。本项目的主要研究目标如下：确定皮质类固醇转运蛋白在细胞和组织水平的定位研究哪些转运蛋白具有皮质类固醇转运的能力研究在远端肾单位细胞模型中删除已鉴定的转运蛋白的影响

Corticosteroids are critical volume-regulating hormones which target the collecting duct of the kidney where they rapidly alter Na+ and H2O transport, a process which underpins the finetuning of total body Na+ balance and maintains our circulating volume. Under physiological conditions the mineralocorticoid aldosterone acts specifically in the collecting duct due to the activity of the enzyme 11HSD2 which converts the much more abundant glucocorticoid cortisol to an inactive metabolite. However, under certain conditions, glucocorticoids may also stimulate Na+ transport. Much is known about the steroid receptors that these hormones bind, subsequent transcriptional events and their effects upon ion transport. Little, however, is known regarding the movement of these hormones beyond their lipophilic nature, endowing them the ability to diffuse freely across plasma membranes.The Mansley lab have generated transcriptomic profiles mapping the genetic signals underpinning corticosteroid-induced Na+ transport in a cellular model of the collecting duct. This work identified several families of membrane transporters whose expression are regulated by acute treatment with corticosteroids. Preliminary studies revealed that corticosteroids may in fact be actively transported in a directed manner, with asymmetrical distribution of hormones on either side of the monolayer and negligible intracellular concentrations. Whilst little has been described in the field regarding active corticosteroid transport specifically in the collecting duct, other groups have shown that corticosteroids can be actively transported elsewhere in the body e.g. brain and adipose tissue. The key research aims of the project are as follows:To determine the localisation of putative corticosteroid transporters at cellular and tissue levelTo investigate which of the putative transporters are capable of corticosteroid transportTo determine the effects of deleting the identified transporter(s) in a cellular model of the distal nephron