Mahdi Fakhri, Shariat-Madar Zia, Schmaier Alvin H
Department of Internal Medicine, Hematology and Oncology Division, the University of Michigan, Ann Arbor, Michigan 48109-0640, USA.
J Biol Chem. 2003 Nov 7;278(45):43983-90. doi: 10.1074/jbc.M304239200. Epub 2003 Aug 27.
Investigations determined the relative preference of prekallikrein (PK) or factor XI/XIa (FXI/FXIa) binding to endothelial cells (HUVECs). In microtiter plates, biotinylated high molecular weight kininogen (biotin-HK) or biotin-FXI binding to HUVEC monolayers or their matrix proteins, but not fibronectin-coated plastic microtiter plate wells, was specifically blocked by antibodies to each of the receptors of HK, uPAR, gC1qR, or cytokeratin 1. Fluorescein isothiocyanate (FITC)-PK specifically bound to HUVEC suspensions without added Zn2+, whereas FITC-FXI or -FXIa binding to HUVEC suspensions required 10 microM added Zn2+ to support specific binding. Plasma concentrations of FXI did not block FITC-PK binding to HUVECs in the absence or presence of 10 microM Zn2+. In the absence of HK, the level of FITC-FXI or -FXIa binding was half that seen in its presence. At physiologic concentrations, PK (450 nM) abolished FITC-FXI or -FXIa binding to HUVEC suspensions in the absence or presence of HK in the presence of 10 microM Zn2+. Released Zn2+ from 2-8 x 10(8) collagen-activated platelets/ml supported biotin-FXI binding to HUVEC monolayers, but platelet activation was not necessary to support biotin-PK binding to HUVECs. At physiologic concentrations, PK also abolished FXI binding to HUVECs in the presence of activated platelets, but FXI did not influence PK binding. PK in the presence or absence of HK preferentially bound to HUVECs over FXI or FXIa. Elevated Zn2+ concentrations are required for FXI but not PK binding, but the presence of physiologic concentrations of PK and HK also prevented FXI binding. PK preferential binding to endothelial cells contributes to their anticoagulant nature.
研究确定了前激肽释放酶（PK）或因子XI/XIa（FXI/FXIa）与内皮细胞（人脐静脉内皮细胞，HUVECs）结合的相对偏好性。在微量滴定板中，生物素化的高分子量激肽原（生物素-HK）或生物素-FXI与HUVEC单层细胞或其基质蛋白结合，但不与纤连蛋白包被的塑料微量滴定板孔结合，可被针对HK、尿激酶型纤溶酶原激活物受体（uPAR）、gC1qR或细胞角蛋白1的每种受体的抗体特异性阻断。异硫氰酸荧光素（FITC）-PK在不添加Zn2+的情况下特异性结合HUVEC悬浮液，而FITC-FXI或-FXIa与HUVEC悬浮液的结合需要添加10 microM的Zn2+来支持特异性结合。在不存在或存在10 microM Zn2+的情况下，FXI的血浆浓度均不阻断FITC-PK与HUVEC的结合。在不存在HK的情况下，FITC-FXI或-FXIa的结合水平是存在HK时的一半。在生理浓度下，PK（450 nM）在不存在或存在HK且有10 microM Zn2+的情况下，可消除FITC-FXI或-FXIa与HUVEC悬浮液的结合。每毫升2 - 8×10(8)个胶原激活的血小板释放的Zn2+支持生物素-FXI与HUVEC单层细胞的结合，但血小板激活对于支持生物素-PK与HUVEC的结合并非必需。在生理浓度下，PK在存在激活血小板的情况下也可消除FXI与HUVEC的结合，但FXI不影响PK的结合。在存在或不存在HK的情况下，PK比FXI或FXIa更优先结合HUVEC。FXI结合需要升高的Zn2+浓度，而PK结合则不需要，但生理浓度的PK和HK的存在也可阻止FXI的结合。PK对内皮细胞的优先结合有助于其抗凝特性。
