Brautigan D L, Randazzo P, Shriner C, Fain J N
Lipids. 1985 Jul;20(7):492-5. doi: 10.1007/BF02534242.
This study investigated a possible role for the epidermal growth factor (EGF) receptor protein tyrosine kinase in phosphoinositide metabolism with plasma membrane vesicles from human epidermoid carcinoma (A431) cells. We found a novel chloroform-soluble product radiolabeled with [gamma-32P]ATP that did not migrate from the origin in the thin layer system designed to separate the phosphoinositides, appeared as a single band of Mr = 3500 on polyacrylamide gels in the presence of dodecyl sulfate, had an ultraviolet absorbance spectrum with a maximum at 275 nm and stained with Coomassie dye. Based on these properties this phosphorylation product is referred to as a proteolipid. The 32P label was not detected in phosphotyrosine [Tyr(P)], phosphoserine [Ser(P)] or phosphothreonine [Thr(P)] and was lost during acid or base hydrolysis. Phosphorylation of proteolipid was increased significantly by EGF, whereas phosphorylation of phosphatidic acid was decreased and labeling of phosphoinositides was unaffected. Thus, it appears that in A431 membranes the EGF receptor/kinase does not utilize phosphatidylinositol as a substrate, but does phosphorylate a membrane proteolipid.
本研究利用人表皮样癌（A431）细胞膜囊泡，对表皮生长因子（EGF）受体蛋白酪氨酸激酶在磷酸肌醇代谢中的可能作用进行了研究。我们发现了一种新的可溶于氯仿的产物，它由[γ-32P]ATP进行放射性标记，在用于分离磷酸肌醇的薄层系统中不离开原点迁移，在十二烷基硫酸钠存在下的聚丙烯酰胺凝胶上呈现为一条Mr = 3500的单带，具有最大吸收波长在275 nm的紫外吸收光谱，并能被考马斯染料染色。基于这些特性，这种磷酸化产物被称为蛋白脂质。在磷酸酪氨酸[Tyr(P)]、磷酸丝氨酸[Ser(P)]或磷酸苏氨酸[Thr(P)]中未检测到32P标记，并且在酸或碱水解过程中标记丢失。EGF可显著增加蛋白脂质的磷酸化，而磷脂酸的磷酸化减少，磷酸肌醇的标记不受影响。因此，在A431细胞膜中，EGF受体/激酶似乎不利用磷脂酰肌醇作为底物，但确实会使一种膜蛋白脂质磷酸化。
