Yoshida J, Takamura S, Ishibashi T, Nishio M
Department of Pharmacology, Kanazawa Medical University, Ishikawa, Japan.
Anticancer Res. 1999 May-Jun;19(3A):1865-71.
An acidic glycoprotein (SAGP) purified from an extract of Streptococcus pyogenes has been shown to inhibit the growth of methylcholanthrene-induced fibrosarcoma A (Meth A) cells via pertussis toxin-sensitive GTP-binding protein. The present study revealed that SAGP has activity to induce apoptosis in Meth A cells as assessed by DNA fragmentation and cell morphology with chromatin staining. The SAGP-induced DNA fragmentation in Meth A cells was augmented by herbimycin A, an inhibitor of protein tyrosine kinase, and prevented by orthovanadate, an inhibitor of protein tyrosine phosphatase. The growth inhibitory effect of SAGP on Meth A cells was reduced by orthovanadate, whereas the effect tended to be increased by herbimycin A. Western blotting analysis using antiphosphotyrosine antibody demonstrated that tyrosine phosphorylation of 170 kDa cellular protein was diminished in the cells incubated with SAGP. The inhibition of protein tyrosine phosphorylation was neither observed in the cells incubated with SAGP and orthovanadate nor in the cells incubated with heat-inactivated SAGP. These findings indicate that inhibition of tyrosine phosphorylation by protein tyrosine phosphatase(s) may be responsible for the SAGP-induced apoptosis and inhibition of cell growth.
从化脓性链球菌提取物中纯化得到的一种酸性糖蛋白（SAGP）已被证明可通过百日咳毒素敏感的GTP结合蛋白抑制甲基胆蒽诱导的纤维肉瘤A（Meth A）细胞的生长。本研究表明，通过DNA片段化和染色质染色的细胞形态学评估，SAGP具有诱导Meth A细胞凋亡的活性。蛋白酪氨酸激酶抑制剂赫曲霉素A可增强SAGP诱导的Meth A细胞DNA片段化，而蛋白酪氨酸磷酸酶抑制剂原钒酸钠则可阻止这种片段化。原钒酸钠可降低SAGP对Meth A细胞的生长抑制作用，而赫曲霉素A则倾向于增强这种作用。使用抗磷酸酪氨酸抗体的蛋白质印迹分析表明，在用SAGP孵育的细胞中，170 kDa细胞蛋白的酪氨酸磷酸化减少。在用SAGP和原钒酸钠孵育的细胞以及用热灭活的SAGP孵育的细胞中均未观察到蛋白质酪氨酸磷酸化的抑制。这些发现表明，蛋白酪氨酸磷酸酶对酪氨酸磷酸化的抑制可能是SAGP诱导细胞凋亡和抑制细胞生长的原因。
