BIGH3 WILD TYPE AND MUTANT PROTEINS

几种角膜营养不良[颗粒状角膜营养不良（GCD），晶格状角膜营养不良（LCD） I型和IIIA型，合并UCD-LCD I型，Thiel-Behnke营养不良和Reis-Bucklers营养不良]被发现是由BIGH3突变引起的。这些情况的特点是角膜内沉积的蛋白质与抗体β -ig-h3 （BIGH3基因的蛋白质产物）反应。对于每一种营养不良，积聚都具有特征性的超微结构。本研究旨在从不同类型的BIGH3角膜营养不良症患者和非BIGH3角膜营养不良症患者的血浆中，以及从COS- 7、CHO-K1和杆状病毒感染的昆虫细胞培养物中纯化β - igg -h3，并对其进行鉴定。将比较野生型和突变型β -ig-h3蛋白，以验证BIGH3角膜营养不良患者角膜内积累的蛋白结构与突变蛋白有关的假设，以及不同表型与BIGH3基因型和突变蛋白表达量之间存在关系的假设。在某些BIGH3角膜营养不良症中积累的淀粉样蛋白的性质及其产生的原因将被研究。我们将确定BIGH3相关淀粉样蛋白是否是突变β -ig-h3的特定片段。由于β -ig-h3与细胞外基质的成分相互作用，我们将试图确定蛋白-蛋白相互作用，这可能解释了BIGH3角膜营养不良症的积累。β -ig-h3的生物合成将在兔角膜上皮细胞中进行表征。

Several corneal dystrophies [granular corneal dystrophy (GCD), lattice corneal dystrophy (LCD) types I and IIIA, combined UCD-LCD type I, Thiel-Behnke dystrophy and Reis-Bucklers dystrophy] have been found to result from mutations in BIGH3. These conditions are characterized by the deposition within the cornea of proteins that react with antibodies to beta-ig-h3 (the protein product of the BIGH3 gene). For each dystrophy the accumulations have a characteristic ultrastructure. This proposal is to purify and characterize beta-ig-h3 from plasma of persons with and without different BIGH3 corneal dystrophies and from cell cultures of COS- 7, CHO-K1 and baculovirus infected insect cells transfected with vectors containing the mutations that produce BIGH3 corneal dystrophies. Wild-type and mutant beta-ig-h3 proteins will be compared to test the hypothesis that the structure of the proteins that accumulate within the cornea in the BIGH3 corneal dystrophies are related to the mutated protein and that a relationship exists between different phenotypes and the BIGH3 genotypes and between the amount of the mutant protein that is expressed. The nature of the amyloid that accumulates in certain BIGH3 corneal dystrophies and the reason for its production will be investigated. We will determine whether BIGH3 related amyloid is a specific fragment of mutant beta-ig-h3. Because beta-ig-h3 interacts with components of the extracellular matrix we will attempt to identify protein- protein interactions that may account for the accumulations that characterize the BIGH3 corneal dystrophies. The biosynthesis of beta-ig-h3 will be characterized in rabbit corneal epithelial cells.