Gentleman S, Reid T W, Martensen T M
Exp Eye Res. 1987 Apr;44(4):587-94. doi: 10.1016/s0014-4835(87)80166-5.
Incubation of quiescent Nakano mouse lens epithelial cells with sodium orthovanadate resulted in time- and concentration-dependent stimulation of protein tyrosine phosphorylation levels in the cells. Protein tyrosine phosphorylation in the 27,000 g pellet showed a 100% stimulation by vanadate. However, upon detergent solubilization, 30% activation of basal endogenous tyrosine phosphorylation was observed but no additional increase was obtained with vanadate. Protein phosphotyrosine phosphatase activity was found in both pellet and cytosolic fractions of the cell. Vanadate inhibited these activities with an IC50 of 57 microM in the cytosolic fraction and 3 microM in the pellet. These data suggest that vanadate increases phosphotyrosine protein levels in these cells by inhibition of a membrane-associated tyrosine-specific phosphatase rather than by activation of protein tyrosine kinases. These data correlate well with the vanadate stimulation of DNA synthesis in these cells, thus indicating a role for phosphotyrosine proteins in regulation of cell division in these cells.
用原钒酸钠孵育静止的中野小鼠晶状体上皮细胞，会导致细胞中蛋白质酪氨酸磷酸化水平出现时间和浓度依赖性的刺激。在27,000g沉淀中的蛋白质酪氨酸磷酸化显示钒酸盐刺激了100%。然而，经去污剂溶解后，观察到基础内源性酪氨酸磷酸化有30%的激活，但钒酸盐并未使其进一步增加。在细胞的沉淀和胞质部分均发现了蛋白质磷酸酪氨酸磷酸酶活性。钒酸盐抑制这些活性，在胞质部分的IC50为57 microM，在沉淀中的IC50为3 microM。这些数据表明，钒酸盐通过抑制膜相关的酪氨酸特异性磷酸酶而非激活蛋白质酪氨酸激酶来增加这些细胞中的磷酸酪氨酸蛋白水平。这些数据与钒酸盐对这些细胞中DNA合成的刺激密切相关，从而表明磷酸酪氨酸蛋白在这些细胞的细胞分裂调节中起作用。
