Matveev Sergey V, Smart Eric J
Department of Physiology, University of Kentucky Medical School, 800 Rose Street, Lexington, KY 40536, USA.
Am J Physiol Cell Physiol. 2002 Apr;282(4):C935-46. doi: 10.1152/ajpcell.00349.2001.
Epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) receptors have been reported to signal via caveolin-containing membranes called caveolae. In contrast, others report that EGF and PDGF receptors are exclusively associated with caveolin-devoid membranes called rafts. Our subcellular fractionation and coimmunoprecipitation studies demonstrate that, in the absence of ligand, EGF and PDGF receptors are associated with rafts. However, in the presence of ligand, EGF and PDGF receptors transiently associate with caveolae. Surprisingly, pretreatment of cells with EGF prevents PDGF-dependent phosphorylation of PDGF receptors and extracellular signal-regulated kinase (ERK) 1/2 kinase activation. Furthermore, cells pretreated with PDGF prevent EGF-dependent phosphorylation of EGF receptors and ERK1/2 kinase activation. Radioligand binding studies demonstrate that incubation of cells with EGF or PDGF causes both EGF and PDGF receptors to be reversibly sequestered from the extracellular space. Experiments with methyl-beta-cyclodextrin, filipin, and antisense caveolin-1 demonstrate that sequestration of the receptors is dependent on cholesterol and caveolin-1. We conclude that ligand-induced stimulation of EGF or PDGF receptors can cause the heterologous desensitization of the other receptor by sequestration in cholesterol-rich, caveolin-containing membranes or caveolae.
据报道，表皮生长因子（EGF）和血小板衍生生长因子（PDGF）受体通过称为小窝的含小窝蛋白的膜发出信号。相比之下，其他人报道EGF和PDGF受体仅与称为脂筏的不含小窝蛋白的膜相关。我们的亚细胞分级分离和共免疫沉淀研究表明，在没有配体的情况下，EGF和PDGF受体与脂筏相关。然而，在有配体的情况下，EGF和PDGF受体与小窝短暂相关。令人惊讶的是，用EGF预处理细胞可阻止PDGF受体的PDGF依赖性磷酸化和细胞外信号调节激酶（ERK）1/2激酶激活。此外，用PDGF预处理的细胞可阻止EGF受体的EGF依赖性磷酸化和ERK1/2激酶激活。放射性配体结合研究表明，用EGF或PDGF孵育细胞会导致EGF和PDGF受体都从细胞外空间可逆性隔离。用甲基-β-环糊精、制霉菌素和小窝蛋白-1反义寡核苷酸进行的实验表明，受体的隔离依赖于胆固醇和小窝蛋白-1。我们得出结论，配体诱导的EGF或PDGF受体刺激可通过在富含胆固醇、含小窝蛋白的膜或小窝中隔离而导致另一种受体的异源脱敏。
