Flückiger Rudolf, Cocuzzi Enzo, Nagaraj Ram H, Shoham Menachem, Kern Timothy S, Medof M Edward
Harvard Medical School, Boston, MA, USA.
Institute of Pathology, Case Western Reserve University, Cleveland, OH, USA.
Mol Immunol. 2018 Jan;93:246-252. doi: 10.1016/j.molimm.2017.06.036. Epub 2017 Sep 5.
Decay accelerating factor (DAF or CD55) is a cell associated C3 and C5 convertase regulator originally described in terms of protection of self-cells from systemic complement but now known to modulate adaptive T cell responses. It is expressed on all cell types. We investigated whether nonenzymatic glycation could impair its function and potentially be relevant to complications of diabetes mellitus and other conditions that result in nonenzymatic glycation including cancer, Alzheimer's disease, and aging. Immunoblots of affinity-purified DAF from erythrocytes of patients with diabetes showed pentosidine, glyoxal-AGEs, carboxymethyllysine, and argpyrimidine. HPLC/MS analyses of glucose modified DAF localized the sites of AGE modifications to K adjacent to K, K at the junction of CCPs2-3 and spatially near R, and R, all identified as being critical for DAF's function. Functional analyses of glucose or ribose treated DAF protein showed profound loss of its regulatory activity. The data argue that de-regulated activation of systemic complement and de-regulated activation of T cells and leukocytes could result from non-enzymatic glycation of DAF.
衰变加速因子（DAF 或 CD55）是一种与细胞相关的 C3 和 C5 转化酶调节剂，最初被描述为保护自身细胞免受全身补体攻击，但现在已知其可调节适应性 T 细胞反应。它在所有细胞类型上均有表达。我们研究了非酶糖基化是否会损害其功能，并可能与糖尿病并发症以及其他导致非酶糖基化的病症（包括癌症、阿尔茨海默病和衰老）相关。对糖尿病患者红细胞中亲和纯化的 DAF 进行免疫印迹分析，结果显示存在戊糖苷、乙二醛晚期糖基化终末产物（AGEs）、羧甲基赖氨酸和精氨嘧啶。对葡萄糖修饰的 DAF 进行高效液相色谱/质谱分析，将 AGE 修饰位点定位到与赖氨酸相邻的赖氨酸、CCP2 - 3 交界处的赖氨酸以及空间上靠近精氨酸的精氨酸，所有这些位点均被确定对 DAF 的功能至关重要。对葡萄糖或核糖处理的 DAF 蛋白进行功能分析，结果显示其调节活性大幅丧失。这些数据表明，DAF 的非酶糖基化可能导致全身补体的失调激活以及 T 细胞和白细胞的失调激活。
