Schuh S M, Newberry E P, Dalton M A, Pike L J
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110.
Mol Biol Cell. 1994 Jul;5(7):739-46. doi: 10.1091/mbc.5.7.739.
We have shown previously that the epidermal growth factor (EGF) receptor is phosphorylated at Ser-1002 and that this phosphorylation is associated with desensitization of the EGF receptor. Ser-1002 is followed immediately by Pro-1003, a residue that may promote the adoption of a specific conformation at this site or severe as a recognition element for the interaction of the EGF receptor with other proteins. To examine these possibilities, we have mutated Pro-1003 of the EGF receptor to a Gly residue and have analyzed the effect of this mutation on EGF-stimulated signaling. Cells expressing the P1003G EGF receptors exhibited higher EGF-stimulated autophosphorylation and synthetic peptide phosphorylation compared to cells expressing wild-type EGF receptors. In addition, the ability of EGF to stimulate PI 3-kinase activity and mitogen-activated protein kinase activity was enhanced in cells expressing the P1003G EGF receptor. Cells expressing P1003G receptors also demonstrated an increased ability to form colonies in soft agar in response to EGF. These results indicate that mutation of Pro-1003 leads to a potentiation of the biological effects of EGF. The findings are consistent with the hypothesis that Pro-1003 plays a role in a form of regulation that normally suppresses EGF receptor function.
我们之前已经表明，表皮生长因子（EGF）受体在Ser-1002位点发生磷酸化，且这种磷酸化与EGF受体的脱敏作用相关。Ser-1002紧接着是Pro-1003，该残基可能促使此位点采用特定构象，或者作为EGF受体与其他蛋白质相互作用的识别元件。为了探究这些可能性，我们将EGF受体的Pro-1003突变为甘氨酸残基，并分析了这种突变对EGF刺激信号传导的影响。与表达野生型EGF受体的细胞相比，表达P1003G EGF受体的细胞在EGF刺激下表现出更高的自身磷酸化和合成肽磷酸化水平。此外，在表达P1003G EGF受体的细胞中，EGF刺激PI 3激酶活性和丝裂原活化蛋白激酶活性的能力增强。表达P1003G受体的细胞对EGF的反应还表现出在软琼脂中形成集落的能力增强。这些结果表明，Pro-1003的突变导致EGF生物学效应的增强。这些发现与以下假设一致，即Pro-1003在一种通常抑制EGF受体功能的调节形式中发挥作用。
