Miles L A, Plow E F
Department of Immunology, Research Institute of Scripps Clinic, La Jolla, CA 92037.
Thromb Haemost. 1987 Oct 28;58(3):936-42.
Glu-plasminogen binds to platelets; the monocytoid line, U937, and the human fetal fibroblast line, GM1380 bind both plasminogen and its activator, urokinase. This study assesses the interaction of these fibrinolytic proteins with circulating human blood cells. Plasminogen bound minimally to red cells but bound saturably and reversibly to monocytes, granulocytes and lymphocytes with apparent Kd values of 0.9-1.4 microM. The interactions were of high capacity with 1.6 to 49 X 10(5) sites/cell and involved the lysine binding sites of plasminogen. Both T cells and non-rosetting lymphocytes and two B cell lines saturably bound plasminogen. Urokinase bound saturably to granulocytes, monocytes, non-rosetting lymphocytes and a B cell line, but minimally to T cells, platelets and red cells. Therefore, plasminogen binding sites of high capacity, of similar affinities, and with common recognition specificities are expressed by many peripheral blood cells. Urokinase receptors are also widely distributed, but less so than plasminogen binding sites. The binding of plasminogen and/or urokinase to these cells may lead to generation of cell-associated proteolytic activity which contributes to a variety of cellular functions.
谷氨酸纤溶酶原与血小板结合；单核细胞系U937以及人胎儿成纤维细胞系GM1380既能结合纤溶酶原又能结合其激活剂尿激酶。本研究评估了这些纤溶蛋白与循环中的人血细胞之间的相互作用。纤溶酶原与红细胞的结合极少，但能以饱和且可逆的方式与单核细胞、粒细胞和淋巴细胞结合，其表观解离常数（Kd）值为0.9 - 1.4微摩尔。这种相互作用具有高结合容量，每个细胞有1.6至49×10⁵个位点，且涉及纤溶酶原的赖氨酸结合位点。T细胞、非花环形成淋巴细胞以及两个B细胞系都能饱和性地结合纤溶酶原。尿激酶能饱和性地与粒细胞、单核细胞、非花环形成淋巴细胞以及一个B细胞系结合，但与T细胞、血小板和红细胞的结合极少。因此，许多外周血细胞都表达具有高结合容量、相似亲和力以及共同识别特异性的纤溶酶原结合位点。尿激酶受体也广泛分布，但不如纤溶酶原结合位点分布广泛。纤溶酶原和/或尿激酶与这些细胞的结合可能导致细胞相关蛋白水解活性的产生，这有助于多种细胞功能的实现。
