Departamento de Biologia Celular e Desenvolvimento, Instituto de Ciências Biomédicas, Av. Prof. Lineu Prestes, 1524, Universidade de São Paulo, São Paulo 05508-900, SP, Brazil ; Departamento de Bioquímica, Instituto de Química, Av. Prof. Lineu Prestes, 748, Universidade de São Paulo, São Paulo 05508-900, SP, Brazil.
FEBS Open Bio. 2012 Apr 24;2:93-7. doi: 10.1016/j.fob.2012.04.006. Print 2012.
Maspin is a tumor suppressor with many biological activities, multiple ligands and different subcellular localizations. Its underlying molecular mechanism remains elusive. We hypothesized that phosphorylation might regulate maspin localization and function. Using two-dimensional gel electrophoresis with different focusing power followed by Western blot we identified four different maspin forms with the same molecular weight (42 kDa), but different isoelectric points. Three of these forms were sensitive to acidic phosphatase treatment, suggesting that they are phosphorylated. Sodium peroxidovanadate treatment, a protein-tyrosine phosphatase inhibitor, resulted in a rapid increase in maspin protein levels and cytoplasmic accumulation. These data show that there are three different maspin tyrosine phosphoforms. Inhibition of tyrosine phosphatases increased maspin protein levels and leads to its cytoplasmic accumulation.
Maspin 是一种具有多种生物活性、多个配体和不同亚细胞定位的肿瘤抑制因子。其潜在的分子机制尚不清楚。我们假设磷酸化可能调节 maspin 的定位和功能。我们使用具有不同聚焦能力的二维凝胶电泳，然后进行 Western blot，鉴定出四种不同的 maspin 形式，它们具有相同的分子量（42 kDa），但等电点不同。其中三种形式对酸性磷酸酶处理敏感，提示它们发生了磷酸化。过氧钒酸钠处理，一种蛋白酪氨酸磷酸酶抑制剂，导致 maspin 蛋白水平的快速增加和细胞质积累。这些数据表明存在三种不同的 maspin 酪氨酸磷酸化形式。抑制酪氨酸磷酸酶增加了 maspin 蛋白水平，并导致其细胞质积累。
