Misra U K, Pizzo S V
Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Cell Signal. 1998 Jun;10(6):441-5. doi: 10.1016/s0898-6568(97)00171-x.
Ligation of the alpha2-macroglobulin signalling receptor (alpha2MSR) with alpha2-macroglobulin (alpha2M)-methylamine or a cloned and expressed receptor binding fragment (RBF) stimulates DNA synthesis. To examine the possible role of the Ras pathway in the mitogenic effects observed on ligating alpha2MSR, we studied the formation of p2 Ras-GTP in murine peritoneal macrophages upon treatment with alpha2M-methylamine and RBF, respectively. Both alpha2M-methylamine (50 pM) and RBF (50 pM) stimulated a 2-3-fold increase in the formation of the p21Ras-GTP complex compared with unstimulated cells. p21Ras-GT32P complex formation was both time and RBF concentration dependent and was comparable to p21Ras-GT32P complex formation induced by EGF (200 ng/mL) and platelet derived growth factor (50 mg/mL). Up-regulation of cells with phorbol dibutyrate prior to stimulation with RBF had no effect on p2 Ras-GT32P formation. However, treatment of macrophages with the tyrosine kinase inhibitor genestein drastically reduced RBF-induced formation of the p21 Ras-GT32P complex. Wortmannin, an inhibitor of phosphatidylinositol-3'-kinase (PI3K), had no effect on p21Ras-GT32P complex formation. It is concluded that the mitogenic effects of ligating alpha2MSR are mediated through a Ras-dependent pathway.
用α2-巨球蛋白（α2M）-甲胺或克隆并表达的受体结合片段（RBF）连接α2-巨球蛋白信号受体（α2MSR）可刺激DNA合成。为了研究Ras途径在连接α2MSR时所观察到的促有丝分裂效应中的可能作用，我们分别研究了用α2M-甲胺和RBF处理后小鼠腹腔巨噬细胞中p21 Ras-GTP的形成。与未刺激的细胞相比，α2M-甲胺（50 pM）和RBF（50 pM）均刺激p21Ras-GTP复合物的形成增加了2-3倍。p21Ras-GT32P复合物的形成既依赖时间也依赖RBF浓度，并且与表皮生长因子（200 ng/mL）和血小板衍生生长因子（50 mg/mL）诱导的p21Ras-GT32P复合物形成相当。在用RBF刺激之前用佛波酯丁酸盐上调细胞对p2 Ras-GT32P的形成没有影响。然而，用酪氨酸激酶抑制剂染料木黄酮处理巨噬细胞可显著降低RBF诱导的p21 Ras-GT32P复合物的形成。磷脂酰肌醇-3'-激酶（PI3K）抑制剂渥曼青霉素对p21Ras-GT32P复合物的形成没有影响。得出的结论是，连接α2MSR的促有丝分裂效应是通过Ras依赖性途径介导的。
