The emergence of ErbB2 expression in cultured rat hepatocytes correlates with enhanced and diversified EGF-mediated signaling
The emergence of ErbB2 expression in cultured rat hepatocytes correlates with enhanced and diversified EGF-mediated signaling
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DOI：
10.1152/ajpgi.00328.2005
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发表时间：
2006-07-01
影响因子：
4.5
通讯作者：
Russell, WE
中科院分区：
文献类型：
--
作者：
Scheving, LA;Zhang, L;Russell, WE
EGF在肝脏中的增殖作用已在培养的肝细胞中被广泛研究。我们研究了EGF，胰岛素和其他生长调节剂对成年大鼠肝细胞原代培养物中ErbB受体的表达，相互作用和信号传导的影响。使用免疫学方法和ErbB酪氨酸激酶抑制剂，我们分析了超过120小时的培养ErbB激酶的表达和信号模式。基础和EGF刺激的蛋白酪氨酸磷酸化增加细胞在体外适应。EGF受体（EGFr）表达下降，而ErbB 3表达上升。虽然ErbB 2不存在于新鲜分离的肝细胞，EGF和胰岛素独立诱导ErbB 2，同时抑制ErbB 3的表达。低浓度的EGF和胰岛素协同刺激ErbB 2表达和DNA合成。ErbB 2（通常由胎儿和新生儿肝细胞表达）的最大增加发生在DNA合成开始前不久（> 40小时）。EGF促进EGFr和ErbB 2共缔合，刺激两种蛋白质的酪氨酸磷酸化。相反，heregulin beta（1）（HRG-beta（1））不促进ErbB 2和ErbB 3的共结合。ErbB 2的选择性tyrphostin抑制剂抑制EGF刺激的DNA合成，但最大的抑制也需要阻断EGFr激酶。最大的EGF刺激DNA合成在体外依赖于ErbB 2的诱导，并涉及EGFr-ErbB 2异二聚体。胰岛素诱导ErbB 2的能力表明胰岛素和EGF之间的协同作用机制以及ErbB 2在体内的可能代谢控制。
The proliferative effects of EGF in liver have been extensively investigated in cultured hepatocytes. We studied the effects of EGF, insulin, and other growth regulators on the expression, interaction, and signaling of ErbB receptors in primary cultures of adult rat hepatocytes. Using immunological methods and ErbB tyrosine kinase inhibitors, we analyzed the expression and signaling patterns of the ErbB kinases over 120 h of culture. Basal and EGF-stimulated protein tyrosine phosphorylation increased as cells adapted in vitro. EGF receptor (EGFr) expression declined in the first 24 h, whereas ErbB3 expression rose. Although ErbB2 was not present in freshly isolated hepatocytes, EGF and insulin independently induced ErbB2 while suppressing ErbB3 expression. Low concentrations of EGF and insulin synergistically stimulated ErbB2 expression and DNA synthesis. The greatest increase in ErbB2, which is normally expressed by fetal and neonatal hepatocytes, occurred shortly before the onset of DNA synthesis (> 40 h). EGF promoted EGFr and ErbB2 coassociation, stimulating tyrosine phosphorylation of both proteins. In contrast, heregulin beta(1) (HRG-beta(1)) did not promote ErbB2 and ErbB3 coassociation. A selective tyrphostin inhibitor of ErbB2 suppressed EGF-stimulated DNA synthesis, but maximum suppression required the blockade of the EGFr kinase as well. Maximal EGF stimulation of DNA synthesis in vitro depends on the induction of ErbB2 and involves an EGFr-ErbB2 heterodimer. The ability of insulin to induce ErbB2 suggests both a mechanism for the synergy between insulin and EGF and a possible metabolic control of ErbB2 in vivo.