Flotillin-1/Reggie-2 Protein Plays Dual Role in Activation of Receptor-tyrosine Kinase/Mitogen-activated Protein Kinase Signaling
Flotillin-1/Reggie-2 Protein Plays Dual Role in Activation of Receptor-tyrosine Kinase/Mitogen-activated Protein Kinase Signaling
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DOI：
10.1074/jbc.m111.287599
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发表时间：
2012-03-02
影响因子：
4.8
通讯作者：
Tikkanen, Ritva
中科院分区：
文献类型：
--
作者：
Amaddii, Monia;Meister, Melanie;Tikkanen, Ritva
我们以前的工作表明，膜微区相关的flotillin蛋白可能参与表皮生长因子（EGF）受体信号转导。在这里，我们表明，敲低flotillin-1/reggie-2的结果减少EGF诱导的特定酪氨酸的EGF受体（EGFR）的磷酸化，并在下游的有丝分裂原活化蛋白（MAP）激酶和Akt信号的激活效率低下。虽然flotillin-1已被牵连在内吞作用，其耗尽既不影响内吞作用，也不泛素化的EGFR。然而，EGF诱导的EGFR在细胞表面的聚集在缺乏flotillin-1的细胞中改变。此外，我们表明，flotillin形成分子复合物与表皮生长因子/表皮生长因子受体激酶独立的方式。然而，敲低flotillin-1似乎更直接地影响下游MAP激酶信号传导的激活。我们在这里表明，flotillin-1与CRAF，MEK 1，ERK和KSR 1（RAS的激酶抑制剂）形成复合物，flotillin-1敲低导致ERK 1/2直接失活。因此，flotillin-1在生长因子信号传导的早期阶段（受体的活化）和晚期阶段（MAP激酶的活化）都起直接作用。我们的研究结果揭示了flotillin-1在经典MAP激酶信号调节中作为支架因子的新作用。此外，我们的研究结果意味着，其他受体酪氨酸激酶也可能依赖于flotillin-1激活后，从而表明flotillin-1作为一种新的因素在recepto-rtyrosine激酶/MAP激酶信号的一般作用。
Our previous work has shown that the membrane microdomain-associated flotillin proteins are potentially involved in epidermal growth factor (EGF) receptor signaling. Here we show that knockdown of flotillin-1/reggie-2 results in reduced EGF-induced phosphorylation of specific tyrosines in the EGF receptor (EGFR) and in inefficient activation of the downstream mitogen-activated protein (MAP) kinase and Akt signaling. Although flotillin-1 has been implicated in endocytosis, its depletion affects neither the endocytosis nor the ubiquitination of the EGFR. However, EGF-induced clustering of EGFR at the cell surface is altered in cells lacking flotillin-1. Furthermore, we show that flotillins form molecular complexes with EGFR in an EGF/EGFR kinase-independent manner. However, knockdown of flotillin-1 appears to affect the activation of the downstream MAP kinase signaling more directly. We here show that flotillin-1 forms a complex with CRAF, MEK1, ERK, and KSR1 (kinase suppressor of RAS) and that flotillin-1 knockdown leads to a direct inactivation of ERK1/2. Thus, flotillin-1 plays a direct role during both the early phase (activation of the receptor) and late (activation of MAP kinases) phase of growth factor signaling. Our results here unveil a novel role for flotillin-1 as a scaffolding factor in the regulation of classical MAP kinase signaling. Furthermore, our results imply that other receptor-tyrosine kinases may also rely on flotillin-1 upon activation, thus suggesting a general role for flotillin-1 as a novel factor in recepto-rtyrosine kinase/MAP kinase signaling.