LAMININS AND GLOMERULAR FILTRATION

肾脏疾病是世界范围内日益普遍的健康问题。原发性肾小球疾病，包括获得性和遗传性疾病，占这些病例的很大比例。我们感兴趣的是了解肾小球滤过屏障的组成，以及它是如何受损和泄漏到血浆蛋白的。在过去的16年里，我们的重点是研究肾小球基底膜（GBM）的组成和功能，这是一种特殊的细胞外基质，是滤过屏障的一个组成部分。GBM含有层粘连蛋白、IV型胶原、氮素和硫酸肝素蛋白多糖。我们对缺乏层粘连蛋白β 2链的小鼠的研究表明，当缺乏层粘连蛋白β 2的小鼠发生肾病综合征和肾衰竭时，GBM本身可以作为白蛋白的屏障，保护足细胞免受血浆蛋白的伤害。人类LAMB2的突变也被证明会导致肾脏疾病；零突变引起皮尔逊综合征（先天性肾病综合征伴有眼部和神经系统异常），而错义突变引起先天性肾病综合征，其肾外表现较轻。我们最近的研究表明，这些错义突变中的一些损害了层粘连蛋白521分泌到GBM中，并且即使突变形式的分泌增加也可能对携带此类突变的患者有益。本提案的重点是寻找改善由于层粘连蛋白异常导致的GBM缺陷患者肾脏疾病的方法，并更好地了解层粘连蛋白聚合在GBM结构和功能中的作用。为了实现这一目标，我们将1)对药物文库进行高通量筛选，寻找能够促进LAMB2突变链在体外分泌的化合物；2)在表达突变层粘连蛋白β 2链的小鼠模型中对这些化合物进行体内测试，以寻找改善分泌和改善过滤屏障的方法；3)表征影响层粘连蛋白聚合的人LAMB2突变的活性和功能。这些研究结果将为层粘连蛋白和基底膜生物学提供重要的新见解，并为涉及GBM缺陷的人类肾小球疾病提供潜在的治疗方法。

DESCRIPTION (provided by applicant): Kidney disease is worldwide health problem that is becoming increasingly prevalent. Primary glomerular disease, both acquired and genetic, represents a significant proportion of these cases. We are interested in understanding the makeup of the glomerular filtration barrier and how it becomes damaged and leaky to plasma proteins. Our focus over the last sixteen years has been to investigate the composition and function of the glomerular basement membrane (GBM), a specialized extracellular matrix that is an integral component of the filtration barrier. The GBM contains laminin, collagen IV, nidogen, and the heparan sulfate proteoglycan agrin. Our studies of mice lacking the laminin beta2 chain suggests that the GBM itself serves as a barrier to albumin and protects podocytes from the injurious effects of plasma proteins, as mice lacking laminin beta2 develop nephrotic syndrome and renal failure. Mutations in human LAMB2 have also been shown to cause kidney disease; null mutations cause Pierson syndrome (congenital nephrotic syndrome with ocular and nervous system abnormalities), whereas missense mutations cause congenital nephrotic syndrome with less severe extrarenal manifestations. Our recent studies have shown that some of these missense mutations impair secretion of laminin-521 into the GBM, and that increased secretion of even mutant forms could be beneficial for patients carrying such mutations. The focus of this proposal is to find methods to ameliorate kidney disease in patients with GBM defects due to laminin abnormalities and to better understand the role of laminin polymerization in GBM structure and function. To accomplish this, we will 1) perform high throughput screens of drug libraries to find compounds that can promote secretion of mutant LAMB2 chains in vitro; 2) test these compounds in vivo in our mouse models expressing mutant laminin beta2 chains to look for improved secretion and an improved filtration barrier; and 3) characterize activity and function of a human LAMB2 mutation that affects laminin polymerization. The results of these studies will provide important new insights into laminin and basement membrane biology and lead to potential therapies for human glomerular disease involving GBM defects.