Pischel K D, Bluestein H G, Woods V L
Department of Medicine, University of California Medical Center, San Diego 92103.
J Clin Invest. 1988 Feb;81(2):505-13. doi: 10.1172/JCI113348.
The very late activation antigens (VLA) are a subset of the superfamily of cell surface glycoproteins that serve as receptors from extracellular matrix proteins. One or more of the VLA heterodimers are present on T lymphocytes and most other cell types, including platelets. We have used VLA-specific monoclonal antibodies to isolate the reactive platelet membrane molecules. We have identified them as previously characterized platelet surface glycoproteins and have compared them with VLA molecules isolated from lymphocytes and other cells. Utilizing one-dimensional SDS-PAGE, two-dimensional O'Farrell gel electrophoresis, and nonreduced-reduced two-dimensional gel electrophoresis, we show that reduced VLA molecules of platelets are composed of three chains of molecular weights 165,000, 145,000, and 140,000 that possess the physicochemical properties of platelet glycoproteins GPIa, GPIc alpha, and GPIIa. GPIa corresponds to the VLA 165,000 alpha 2-chain, GPIIa corresponds to a 145,000 Mr VLA beta-chain, and GPIc alpha corresponds to a 140,000 Mr VLA alpha-chain. The polypeptide structure of VLA molecules on platelets and lymphocytes are very similar or identical. Platelet proteins GPIa and GPIIa exist as a mixed heterodimer in detergent lysates and correspond with the VLA-2 heterodimer found on activated T lymphocytes and other cell types. The platelet glycoproteins GPIIa and GPIc form a second mixed heterodimer. The mAb A-1A5, which binds to the VLA beta chain, binds to platelet GPIIa and precipitates both the GPIIa-GPIa and GPIIa-GPIc heterodimers, and binds to 4,926 +/- 740 sites per platelet. A VLA-2-specific mAb, 12F1, which binds to the VLA alpha 2-chain reacts with GPIa and immunoprecipitates only the GPIIa-GPIa heterodimer, and binds to 1,842 +/- 449 sites per platelet. The similarity of VLA chains and platelet GPIIa, GPIa, and GPIc molecules suggests that these molecules may have similar functions on various cell types.
极晚期活化抗原（VLA）是细胞表面糖蛋白超家族的一个亚群，作为细胞外基质蛋白的受体。一种或多种VLA异二聚体存在于T淋巴细胞和大多数其他细胞类型中，包括血小板。我们使用VLA特异性单克隆抗体来分离反应性血小板膜分子。我们已将它们鉴定为先前已表征的血小板表面糖蛋白，并将它们与从淋巴细胞和其他细胞中分离的VLA分子进行了比较。利用一维SDS-PAGE、二维奥法雷尔凝胶电泳和非还原-还原二维凝胶电泳，我们表明血小板的还原VLA分子由分子量为165,000、145,000和140,000的三条链组成，它们具有血小板糖蛋白GPIa、GPIcα和GPIIa的物理化学性质。GPIa对应于VLA 165,000α2链，GPIIa对应于145,000 Mr的VLAβ链，GPIcα对应于140,000 Mr的VLAα链。血小板和淋巴细胞上VLA分子的多肽结构非常相似或相同。血小板蛋白GPIa和GPIIa在去污剂裂解物中以混合异二聚体形式存在，与活化T淋巴细胞和其他细胞类型上发现的VLA-2异二聚体相对应。血小板糖蛋白GPIIa和GPIc形成第二种混合异二聚体。与VLAβ链结合的单克隆抗体A-1A5与血小板GPIIa结合，并沉淀GPIIa-GPIa和GPIIa-GPIc异二聚体，每个血小板结合4,926±740个位点。与VLAα2链结合的VLA-2特异性单克隆抗体12F1与GPIa反应，仅免疫沉淀GPIIa-GPIa异二聚体，每个血小板结合1,842±449个位点。VLA链与血小板GPIIa、GPIa和GPIc分子的相似性表明这些分子在各种细胞类型上可能具有相似的功能。
