LAMB3在肾小管细胞结构和功能维持中的作用及其遗传突变的后果

Laminins, mainly present in the transparent layer of basement membrane, is an important components non-collagen glycoprotein of kidney basement membranes. Laminins are heterotrimers of α, β and γ chains linked by disulfide bonds to form cruciform molecules. To date, five different α chains, three β chains and three γ chains have been identified with different combinations resulting in as many as 15 different laminin isoforms. Laminin 3β (LAMB3) chain is a subunit of Laminin-5. We found a heterozygote missense mutation in the LAMB3 p.R889C in an adult family by whole exon sequencing. Bioinformatics predicts that the mutation can significantly destroy protein function. We detected the expression and distribution of LAMB3 in the kidney by confocal analysis. The LAMB3 is mainly located in the collection duct cells and the Henle's loop. We speculated that LAMB3 may play an important role in the maintenance of kidneys structure and function. Therefore, we will first explore the effects of LAMB3 and Laminin-5 on the adhesion, proliferation, survival, migration and polarity of renal cells, and then explore the molecular mechanism of LAMB3. We will further study the consequences of LAMB3 p.R889C missense mutation. This study will help to understand the function of LAMB3 in the kidney and the pathogenic of the disease caused by genetic mutation.

层粘连蛋白在肾脏主要存在于基底膜的透明层中，是基底膜非胶原糖蛋白的重要成分。人层粘连蛋白有15种，由α、β、γ三个亚单位组成。LAMB3是组成层粘连蛋白5（Laminin-5）的β亚单位。我们在一个成人尿毒症家系中发现LAMB3 p.R889C位点错义突变。生物信息学预测，该突变将显著破坏蛋白功能。由于先证者临床和病理表现为慢性肾小管间质病变，我们对LAMB3在肾脏表达进行定位，发现其在肾小管主要位于集合管和亨利氏襻。我们推测LAMB3可能在正常肾脏结构功能的维持中起着重要作用。为此，我们将首先研究正常LAMB3对肾脏细胞粘附、增殖、存活、迁移和极性的影响，探讨其作用的分子机制。然后我们研究LAMB3 p.R889C错义突变的后果和致病机制。本课题的研究将有助于了解LAMB3在肾脏的功能和作用和认识其遗传突变导致疾病的原因。

层粘连蛋白在肾脏主要存在于基底膜的透明层中，是基底膜非胶原糖蛋白的重要成分。人层粘连蛋白有15种，由α、β、γ三个亚单位组成。LAMB3是组成层粘连蛋白5（Laminin-5）的β亚单位。我们在一个成人尿毒症家系中发现LAMB3 p.R889C位点错义突变。生物信息学预测，该突变将显著破坏蛋白功能。由于先证者临床和病理表现为慢性肾小管间质病变，我们对LAMB3在肾脏表达进行定位，发现其在肾小管主要位于集合管和亨利氏襻。我们将野生型LAMB3和突变型LAMB3 p.R869C过表达，结果发现在高盐刺激下，野生型过表达细胞的增殖能力增加，细胞上清LDH释放较少，普通光学显微镜下显示在高盐刺激下，野生型细胞存活能力增强。而点突变后集合管细胞的增殖能力减弱，细胞上清的LDH释放增加，细胞的存活显著减少。此外，LAMB3过表达，AQP2的表达增加，并且存在部分上膜。提示LAMB3可能在正常肾脏结构功能的维持中起着重要作用。因此，LAMB3 p.R889C突变增加集合管细胞损伤，具有致病性。