Christie M R, Hollands J A, Brown T J, Michelsen B K, Delovitch T L
Nuffield Department of Clinical Biochemistry, John Radcliffe Hospital, Headington, Oxford, United Kingdom.
J Clin Invest. 1993 Jul;92(1):240-8. doi: 10.1172/JCI116556.
Patients with insulin-dependent diabetes (IDDM) possess antibodies to islet proteins of M(r)-64,000. Potential autoantigens of this M(r) include glutamate decarboxylase (GAD) and 65 kD heat shock protein. We have detected two distinct antibody specificities in IDDM that bind 50,000 M(r) or 37,000/40,000 M(r) proteolytic fragments of 64,000 M(r) proteins. In this study, we investigated relationships of these proteolytic fragments to GAD and heat shock proteins. Polyclonal antibodies to GAD bound 50,000 M(r) fragments of islet antigen. Recombinant GAD65, but not GAD67, blocked binding to this antigen, suggesting that 50,000 M(r) fragments are derived from islet GAD65. In contrast, GAD antibodies did not recognize 37,000/40,000 M(r) fragments, and neither GAD isoforms blocked autoantibody binding to precursors of these fragments. The 37,000/40,000 M(r) fragments, but not the 50,000 M(r) fragments, were detected after trypsin treatment of immunoprecipitates from insulinoma cells that lacked expression of major GAD isoforms. Antibodies in IDDM did not bind native or trypsinized islet heat shock proteins. Thus, IDDM patients possess antibodies to GAD, but also distinct antibodies to a 64,000 M(r) protein that is not related to known GAD isoforms or heat shock proteins.
胰岛素依赖型糖尿病（IDDM）患者体内存在针对分子量为64,000的胰岛蛋白的抗体。这种分子量的潜在自身抗原包括谷氨酸脱羧酶（GAD）和65kD热休克蛋白。我们在IDDM患者中检测到两种不同的抗体特异性，它们能结合分子量为64,000的蛋白的50,000或37,000/40,000蛋白水解片段。在本研究中，我们调查了这些蛋白水解片段与GAD和热休克蛋白之间的关系。抗GAD的多克隆抗体能结合胰岛抗原的50,000分子量片段。重组GAD65而非GAD67能阻断与该抗原的结合，这表明50,000分子量片段来源于胰岛GAD65。相反，GAD抗体不能识别37,000/40,000分子量片段，且两种GAD同工型均不能阻断自身抗体与这些片段前体的结合。在对缺乏主要GAD同工型表达的胰岛素瘤细胞的免疫沉淀产物进行胰蛋白酶处理后，检测到了37,000/40,000分子量片段，而未检测到50,000分子量片段。IDDM患者的抗体不与天然或经胰蛋白酶处理的胰岛热休克蛋白结合。因此，IDDM患者不仅存在针对GAD的抗体，还存在针对一种分子量为64,000且与已知GAD同工型或热休克蛋白无关的蛋白的独特抗体。
