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CD 4 T淋巴细胞在1型糖尿病的发病机制中起着关键作用。溶酶体半胱氨酸蛋白酶、组织蛋白酶（Cat）S、L和B涉及抗原加工和由MHC II类分子呈递给CD 4 T细胞。这些酶参与MHC II类相关不变链的蛋白水解降解，并参与从自身和外源抗原产生抗原肽。在这项提案中，我们将研究非肥胖糖尿病易感（NOD）小鼠，这些小鼠对1型糖尿病的易感性与人类相似。我们通过将相应的基因敲除小鼠繁殖到NOD背景中，产生了Cat S、L或B缺陷的NOD小鼠。初步研究表明，与杂合同窝出生的小鼠相比，Cat S和B基因敲除小鼠的糖尿病发病率显著降低。Cat缺陷型小鼠中疾病的减少可能是由于：MHC II类分子的抗原呈递减少;巨噬细胞介导的非特异性炎症减少;自身反应性CD 4 T细胞的发育减少;抑制性T细胞的活性增加;胰岛α细胞中自身抗原产生减少;胰岛α细胞对凋亡的抗性增加。在本提案中，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检验所有这些假设，具体目的如下：1）表征Cat缺陷型和野生型对照NOD小鼠中的疾病进展、MHC II类抗原加工和呈递以及CD 4 T细胞发育; 2）确定组织蛋白酶缺陷型NOD小鼠中糖尿病减少的细胞机制。这项工作将有助于我们了解组织蛋白酶在MHC II类抗原呈递中的作用，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.