ROLE OF CATHEPSINS S, L AND B IN THE TYPE 1 DIABETES

描述(由申请人提供)： 自身反应性MHC II类反应性CD4T淋巴细胞在1型糖尿病的发病机制中起关键作用。溶酶体半胱氨酸蛋白酶、组织蛋白(猫)S、L和B参与了MHC-II类分子对CD4T细胞的抗原加工和递呈。这些酶参与MHC-II类相关不变链的蛋白降解，以及从自身和外源抗原中产生抗原肽。在这项建议中，我们将研究非肥胖糖尿病易感(NOD)小鼠，这些小鼠表现出与人类相似的对1型糖尿病的MHC依赖易感性。我们通过将相应的基因敲除小鼠饲养到NOD背景上，获得了缺乏S、L或B猫的NOD小鼠。初步研究表明，与杂合子小鼠相比，S猫和B基因缺失小鼠的糖尿病发病率显著降低。Cat基因缺陷小鼠疾病的减少可能是由于：MHC-II类分子的抗原提呈减少；巨噬细胞介导的非特异性炎症减少；自身反应性CD4T细胞的发育减少；抑制性T细胞的活性增加；胰岛细胞中自身抗原的产生减少；胰岛a细胞对凋亡的抵抗力增强。在这项建议中，我们将通过研究CAT B、S和L在自发性I型糖尿病中的作用来验证所有这些假说，具体目的如下：1)研究CAT缺陷和野生型对照NOD小鼠的疾病进展、MHC II类抗原的处理和递送以及CD4T细胞的发育；2)确定组织蛋白酶缺陷NOD小鼠降低糖尿病的细胞机制。这项工作将有助于我们理解组织蛋白在MHC-II类抗原提呈中的作用，并为下调导致1型糖尿病的免疫反应提供新的靶点。

DESCRIPTION (provided by applicant): Autoreactive MHC class II-reactive CD4 T lymphocytes play a critical role in the pathogenesis of Type 1 diabetes. Lysosomal cysteine proteinases, cathepsin (Cat) S, L, and B are implicated in antigen processing and presentation by MHC class II molecules to CD4 T cells. These enzymes participate in the proteolytic degradation of MHC class II associated invariant chain and in generation of antigenic peptides from self and foreign antigens. In this proposal, we will study non-obese diabetes prone (NOD) mice, which show MHC-dependent susceptibility to Type 1 diabetes analogous to that seen in humans. We have generated NOD mice deficient in Cat S, L or B by breeding the corresponding knockout mice onto the NOD background. Preliminary studies suggest that incidence of diabetes is significantly reduced in Cat S and B null mice as compared to heterozygous littermates. Reduced disease in Cat deficient mice can be due to: diminished antigen presentation by MHC class II molecules; diminished non-specific inflammation mediated by macrophages; reduced development of autoreactive CD4 T cells; increased activity of suppressor T cells; reduced autoantigen production in the islet _-cells; increased resistance of islet a cells to apoptosis. In this proposal, we will test all these hypotheses by investigating the role of cat B, S and L in spontaneous type I diabetes in the following specific Aims: 1) to characterize disease progression, MHC class II antigen processing and presentation, and CD4 T cell development in Cat-deficient and wild type control NOD mice; 2) to determine cellular mechanisms responsible for reduced diabetes in cathepsin-deficient NOD mice. This work will contribute to our understanding of the role of cathepsins in MHC class II antigen presentation, and provide new targets for downmodulating the immune responses leading to Type 1 diabetes.