外源性锌离子对人呼吸道上皮细胞内肿瘤抑制蛋白PTEN活性的影响及其机制

Inhibitory effects of exogenous zinc on enzymatic activity of tumor suppressor protein PTEN and possible mechanisms in human airway epithelial cells

目的探讨外源性锌离子对人呼吸道上皮细胞肿瘤抑制蛋白PTEN的活性的影响及其机制。方法以人呼吸道上皮细胞株BEAS-2B作为体外模型,应用孔雀绿法测定锌离子对PTEN磷酸酶活性的影响;利用Western Blot法检测锌离子对PTEN蛋白磷酸化的影响。利用酪蛋白激酶2(CK-2)试剂盒测定锌离子对PTEN上游激酶CK-2活性的影响。结果 50μmol/L锌离子刺激可抑制PTEN蛋白磷酸化及其磷酸酶活性(P<0.05)。在相同实验条件下,锌离子刺激还可抑制CK-2的活性(P<0.05)。此外,CK-2可致PTEN磷酸化(P<0.05)。结论外源性锌离子可能通过抑制CK-2的活性进一步抑制人呼吸道上皮细胞内肿瘤抑制蛋白PTEN磷酸酶活性。

Objective To examine the effect of exogenous zinc on enzymatic activity of tumor suppressor PTEN and underlying mechanisms.Methods Human airway epithelial cells（BEAS-2B） were employed as the in vitro model.Enzymatic activity of PTEN was measured using malachite green colorimetric assay and immunoblotting.Moreover,the activity of casein kinase-2（CK-2）,the upstream kinase of PTEN,was determined.Results Exposure of BEAS-2B cells to Zn2＋ inhibited phosphatase activity of PTEN,as well as PTEN phosphorylation,indicative of PTEN activity（P〈0.05）.Under the same experimental condition,Zn2＋ stimulation resulted in significant reduction of CK-2 activity（P〈0.05）.In addition,CK-2 was shown to induce PTEN phosphorylation（P〈0.05）.Conclusion These results suggested that Zn2＋ exposure might inhibit PTEN phosphatase activity through inhibition of CK-2 activity in human airway epithelial cells.