Fibrin(ogen) is internalized and degraded by activated human monocytoid cells via Mac-1 (CD11b/CD18): a nonplasmin fibrinolytic pathway.
Fibrin(ogen) is internalized and degraded by activated human monocytoid cells via Mac-1 (CD11b/CD18): a nonplasmin fibrinolytic pathway.
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DOI：
10.1182/blood.v82.8.2414.bloodjournal8282414
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发表时间：
1993-10
期刊：
影响因子：
20.3
通讯作者：
Daniel I. Simon;A. Ezratty;Stephanie A. Francis;Helmut G. Rennke;Joseph Loscalzo
中科院分区：
文献类型：
--
作者：
Daniel I. Simon;A. Ezratty;Stephanie A. Francis;Helmut G. Rennke;Joseph Loscalzo
纤维蛋白（原）（FGN）对于止血和伤口愈合很重要，并且主要通过纤溶酶原激活剂系统从损伤部位清除。然而，在纤溶酶原激活剂缺陷的转基因小鼠中出现的新证据表明，非纤溶酶途径可能在纤维蛋白（原）溶解中也很重要。鉴于血管损伤部位的闭塞血栓内 FGN 和单核细胞的接近性，我们考虑单核细胞可能在纤维蛋白的降解和清除中发挥辅助作用的可能性。我们发现单核细胞拥有另一种纤溶途径，该途径使用整合素 Mac-1，直接结合并内化 FGN，导致其溶酶体降解。在 4°C 下，FGN 以特异性且可饱和的方式与 U937 单核细胞结合，kd 为 1.8 mumol/L。结合需要二磷酸腺苷刺激并且是钙依赖性的。在37摄氏度下，FGN和纤维蛋白单体(FM)被U937细胞以0.37+/-0.13和0.55+/-0.03微克/10(6)细胞/小时的速率内化和降解，THP-1细胞以1.38+/-0.02和1.20+/-0.30微克/10(6)细胞/小时的速率内化和降解，并且人外周血单核细胞分别为 2.10 +/- 0.20 和 2.52 +/- 0.18 微克/10(6) 细胞/小时。丝氨酸蛋白酶抑制剂 PPACK 和抑肽酶以及特异性弹性蛋白酶抑制剂 AAPVCK 不会显着抑制降解。然而，氯喹抑制降解，表明涉及溶酶体途径。 X 因子是 Mac-1 受体 FGN 的竞争性配体，也能阻止降解，Mac-1 α 亚基的单克隆抗体也能阻止降解。放射性碘标记的内化 FGN 的放射自显影表明，FGN 通过该途径进行蛋白水解，产生与纤溶酶观察到的独特降解模式不同的降解模式。在纤维蛋白凝块溶解测定中，Mac-1 介导的纤维蛋白溶解对总纤维蛋白溶解有显着贡献。总之，在没有纤溶酶的情况下，FGN 被激活的人单核细胞通过 Mac-1 内化和降解，从而提供了另一种纤溶途径。因此，除了细胞粘附的功能外，整联蛋白还可以充当介导结合配体的内化和降解的受体。
Fibrin(ogen) (FGN) is important for hemostasis and wound healing and is cleared from sites of injury primarily by the plasminogen activator system. However, there is emerging evidence in plasminogen activator-deficient transgenic mice that nonplasmin pathways may be important in fibrin(ogen)olysis, as well. Given the proximity of FGN and monocytes within the occlusive thrombus at sites of vascular injury, we considered the possibility that monocytes may play an ancillary role in the degradation and clearance of fibrin. We found that monocytes possess an alternative fibrinolytic pathway that uses the integrin Mac-1, which directly binds and internalizes FGN, resulting in its lysosomal degradation. At 4 degrees C, FGN binds to U937 monocytoid cells in a specific and saturable manner with a kd of 1.8 mumol/L. Binding requires adenosine diphosphate stimulation and is calcium-dependent. At 37 degrees C, FGN and fibrin monomer (FM) are internalized and degraded at rates of 0.37 +/- 0.13 and 0.55 +/- 0.03 microgram/10(6) cells/h by U937 cells, 1.38 +/- 0.02 and 1.20 +/- 0.30 microgram/10(6) cells/h by THP-1 cells, and 2.10 +/- 0.20 and 2.52 +/- 0.18 micrograms/10(6) cells/h by human peripheral blood mononuclear cells, respectively. The serine protease inhibitors, PPACK and aprotinin, and the specific elastase inhibitor, AAPVCK, do not significantly inhibit degradation. However, degradation is inhibited by chloroquine, suggesting that a lysosomal pathway is involved. Factor X, a competitive ligand with FGN for the Mac-1 receptor, also blocks degradation, as does a monoclonal antibody to the alpha-subunit of Mac-1. Autoradiography of radioiodinated, internalized FGN shows that FGN proteolysis by the pathway produces a unique degradation pattern distinct from that observed with plasmin. In a fibrin clot lysis assay, Mac-1-mediated fibrinolysis contributed significantly to total fibrinolysis. In summary, FGN is internalized and degraded by activated human monocytoid cells via Mac-1 in the absence of plasmin, thereby providing an alternative fibrinolytic pathway. Thus, in addition to the function of cell adhesion, integrins may also act as receptors that mediate the internalization and degradation of bound ligands.