Carpentier J L, White M F, Orci L, Kahn R C
Institute of Histology and Embryology, University of Geneva Medical Center, Switzerland.
J Cell Biol. 1987 Dec;105(6 Pt 1):2751-62. doi: 10.1083/jcb.105.6.2751.
Epidermal growth factor (EGF) rapidly stimulates receptor autophosphorylation in A-431 cells. After 1 min the phosphorylated receptor can be identified at the plasma membrane using an anti-phosphotyrosine antibody. With further incubation at 37 degrees C, approximately 50% of the phosphorylated EGF receptor was internalized (t1/2 = 5 min) and associated with the tubulovesicular system and later with multivesicular bodies, but not the nucleus. During this period, there was no change in the extent or sites of phosphorylation. At all times the phosphotyrosine remained on the cytoplasmic side of the membrane, opposite to the EGF ligand identified by anti-EGF antibody. These data indicate that (a) the tyrosine-phosphorylated EGF receptor is internalized in its activated form providing a mechanism for translocation of the receptor kinase to substrates in the cell interior; (b) the internalized receptor remains intact for at least 60 min, does not associate with the nucleus, and does not generate any tyrosine-phosphorylated fragments; and (c) tyrosine phosphorylation alone is not the signal for receptor internalization.
表皮生长因子（EGF）能迅速刺激A - 431细胞中的受体自磷酸化。1分钟后，使用抗磷酸酪氨酸抗体可在质膜上鉴定出磷酸化受体。在37℃下进一步孵育后，约50%的磷酸化EGF受体被内化（半衰期 = 5分钟），并与微管泡系统相关，随后与多囊泡体相关，但不与细胞核相关。在此期间，磷酸化的程度和位点没有变化。在所有时间里，磷酸酪氨酸都保留在膜的细胞质一侧，与抗EGF抗体识别的EGF配体相对。这些数据表明：（a）酪氨酸磷酸化的EGF受体以其活化形式被内化，为受体激酶向细胞内底物的转位提供了一种机制；（b）内化的受体至少60分钟内保持完整，不与细胞核结合，也不产生任何酪氨酸磷酸化片段；（c）仅酪氨酸磷酸化不是受体内化的信号。
