Morris Dionne R, Ding Yu, Ricks Tiffany K, Gullapalli Anuradha, Wolfe Breann L, Trejo JoAnn
Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7365, USA.
Cancer Res. 2006 Jan 1;66(1):307-14. doi: 10.1158/0008-5472.CAN-05-1735.
Protease-activated receptors (PAR) are G protein-coupled receptors that function as cell-surface sensors for coagulant proteases, as well as other proteases associated with the tumor microenvironment. PAR1 is activated by thrombin whereas the upstream coagulant protease VIIa bound to tissue factor and Xa can activate both PAR1 and PAR2. PAR1 has been implicated in tumor cell growth, migration, and invasion whereas the function of PAR2 in these processes is largely unknown. Towards defining the functional importance of PAR2 in cancer cells, we used small interfering RNAs to deplete highly invasive breast cancer cells of endogenous PAR proteins. Our findings strongly suggest that PAR2 is critical for MDA-MB-231 and BT549 breast cancer cell migration and invasion towards NIH 3T3 fibroblast conditioned medium. To define the relative importance of PAR1 versus PAR2 in mediating factor VIIa and Xa responses, we assessed signaling in cancer cells lacking either endogenous PAR1 or PAR2 proteins. Strikingly, in MDA-MB-231 cells depleted of PAR2, we observed a marked inhibition of VIIa and Xa signaling to phosphoinositide hydrolysis and extracellular signal-regulated kinase 1/2 activation whereas signaling by VIIa and Xa remained intact in PAR1-deficient cells. Factor VIIa and Xa-induced cellular migration was also impaired in MDA-MB-231 cells deficient in PAR2 but not in cells lacking PAR1. Together, these studies reveal the novel findings that PAR2, a second protease-activated G protein-coupled receptor, has a critical role in breast cancer cell migration and invasion and functions as the endogenous receptor for coagulant proteases VIIa and Xa in these cells.
蛋白酶激活受体（PAR）是G蛋白偶联受体，作为凝血蛋白酶以及与肿瘤微环境相关的其他蛋白酶的细胞表面传感器发挥作用。PAR1由凝血酶激活，而与组织因子和Xa结合的上游凝血蛋白酶VIIa可激活PAR1和PAR2。PAR1与肿瘤细胞的生长、迁移和侵袭有关，而PAR2在这些过程中的功能 largely未知。为了确定PAR2在癌细胞2在癌细胞中的功能重要性，我们使用小干扰RNA来耗尽高侵袭性乳腺癌细胞中的内源性PAR蛋白。我们的研究结果强烈表明，PAR2对MDA-MB-231和BT549乳腺癌细胞向NIH 3T3成纤维细胞条件培养基的迁移和侵袭至关重要。为了确定PAR1与PAR2在介导因子VIIa和Xa反应中的相对重要性，我们评估了缺乏内源性PAR1或PAR2蛋白的癌细胞中的信号传导。令人惊讶的是，在耗尽PAR2的MDA-MB-231细胞中，我们观察到VIIa和Xa信号对磷酸肌醇水解和细胞外信号调节激酶1/2激活的显著抑制，而VIIa和Xa在缺乏PAR1的细胞中的信号传导保持完整。在缺乏PAR2的MDA-MB-231细胞中，因子VIIa和Xa诱导的细胞迁移也受到损害，但在缺乏PAR1的细胞中则没有。总之，这些研究揭示了新的发现，即PAR2，一种第二种蛋白酶激活的G蛋白偶联受体，在乳腺癌细胞迁移和侵袭中起关键作用，并作为这些细胞中凝血蛋白酶VIIa和Xa的内源性受体发挥作用。
