Kamer A R, Hoghooghi S A, Liebow C
Oral Maxillofacial Department, School of Dental Medicine, SUNY at Buffalo, NY 14214, USA.
Int J Mol Med. 1998 Apr;1(4):735-9. doi: 10.3892/ijmm.1.4.735.
Protein phosphorylation/dephosphorylation on tyrosine residues are regulated by tyrosine kinases/phosphatases. The tyrosine phosphatase SH-PTP2 (PTP1D, PTP2C) interacts physically through its SH2 domain with phosphorylated epidermal growth factor receptor (EGFR). In KB cells, an oral epidermoid carcinoma, high epidermal growth factor (EGF) concentrations (10-9, 10-8 and 10-7 M) downregulate its receptor for the duration of the incubation with EGF. Thus, it was hypothesized that in KB cells, SH-PTP2 expression would also be downregulated by high EGF concentrations. This hypothesis was investigated by incubating the KB cells with increasing concentrations of EGF (0, 10-11, 10-10, 10-9, 10-8, 10-7 M) and by evaluating the expression of SH-PTP2 protein under these conditions. This study showed that EGF 10-7 and 10-8 M significantly decreased SH-PTP2 protein expression compared to controls. EGF 10-10 and 10-11 M did not change the expression of SH-PTP2 protein. We conclude that high EGF concentrations downregulate the expression of SH-PTP2 protein.
酪氨酸残基上的蛋白质磷酸化/去磷酸化由酪氨酸激酶/磷酸酶调节。酪氨酸磷酸酶SH-PTP2（PTP1D，PTP2C）通过其SH2结构域与磷酸化的表皮生长因子受体（EGFR）发生物理相互作用。在口腔表皮样癌KB细胞中，高浓度的表皮生长因子（EGF，10-9、10-8和10-7 M）在与EGF孵育期间会下调其受体。因此，有人推测在KB细胞中，高浓度的EGF也会下调SH-PTP2的表达。通过用浓度不断增加的EGF（0、10-11、10-10、10-9、10-8、10-7 M）孵育KB细胞，并评估这些条件下SH-PTP2蛋白的表达，对这一推测进行了研究。这项研究表明，与对照组相比，10-7和10-8 M的EGF显著降低了SH-PTP2蛋白的表达。10-10和10-11 M的EGF没有改变SH-PTP2蛋白的表达。我们得出结论，高浓度的EGF会下调SH-PTP2蛋白的表达。
