Deb T B, Su L, Wong L, Bonvini E, Wells A, David M, Johnson G R
Divisions of Therapeutic Proteins, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.
J Biol Chem. 2001 May 4;276(18):15554-60. doi: 10.1074/jbc.M100928200. Epub 2001 Feb 5.
The ErbB family of receptors, which includes the epidermal growth factor receptor (EGFR), ErbB2, ErbB3, and ErbB4, mediate signaling by EGF-like polypeptides. To better understand the role of the EGFR tyrosine kinase, we analyzed signaling by a kinase-inactive EGFR (K721M) in ErbB-devoid 32D cells. K721M alone exhibited no detectable signaling capacity, whereas coexpression of K721M with ErbB2, but not ErbB3 or ErbB4, resulted in EGF-dependent mitogen-activated protein kinase (MAPK) activation. The kinase activity, but not tyrosine phosphorylation, of ErbB2 was required for EGF-induced MAPK activation. The presence of tyrosine phosphorylation sites in K721M was not a requisite for signaling, indicating that transphosphorylation of K721M by ErbB2 was not an essential mechanism of receptor activation. Conversely, the mutated kinase domain of K721M (residues 648-973) and tyrosine phosphorylation of at least one of the receptors were necessary. EGF was found to activate the pro-survival protein kinase Akt in stable cell lines expressing K721M and ErbB2 but, unlike cells expressing wild-type EGFR, was incapable of activating signal transducers and activators of transcription (STAT) or driving cell proliferation. These results demonstrate that EGFR-ErbB2 oligomers are potent activators of MAPK and Akt, and this signaling does not require EGFR kinase activity.
受体酪氨酸激酶ErbB家族，包括表皮生长因子受体（EGFR）、ErbB2、ErbB3和ErbB4，介导表皮生长因子样多肽的信号传导。为了更好地理解EGFR酪氨酸激酶的作用，我们分析了激酶失活的EGFR（K721M）在缺乏ErbB的32D细胞中的信号传导。单独的K721M没有可检测到的信号传导能力，而K721M与ErbB2（而非ErbB3或ErbB4）共表达导致了表皮生长因子（EGF）依赖性丝裂原活化蛋白激酶（MAPK）的激活。EGF诱导的MAPK激活需要ErbB2的激酶活性，但不需要其酪氨酸磷酸化。K721M中酪氨酸磷酸化位点的存在不是信号传导的必要条件，这表明ErbB2对K721M的转磷酸化不是受体激活的基本机制。相反，K721M的突变激酶结构域（第648 - 973位氨基酸残基）和至少一种受体的酪氨酸磷酸化是必需的。在表达K721M和ErbB2的稳定细胞系中，发现EGF可激活促生存蛋白激酶Akt，但与表达野生型EGFR的细胞不同，EGF无法激活信号转导子和转录激活子（STAT）或驱动细胞增殖。这些结果表明，EGFR - ErbB2寡聚体是MAPK和Akt的有效激活剂，并且这种信号传导不需要EGFR激酶活性。
