Low Density Lipoprotein Receptor-related Protein 1 (LRP1) Forms a Signaling Complex with Platelet-derived Growth Factor Receptor-β in Endosomes and Regulates Activation of the MAPK Pathway
Low Density Lipoprotein Receptor-related Protein 1 (LRP1) Forms a Signaling Complex with Platelet-derived Growth Factor Receptor-β in Endosomes and Regulates Activation of the MAPK Pathway
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DOI：
10.1074/jbc.m109.046672
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发表时间：
2010-05-07
影响因子：
4.8
通讯作者：
Strickland, Dudley K.
中科院分区：
文献类型：
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作者：
Muratoglu, Selen Catania;Mikhailenko, Irina;Strickland, Dudley K.
除了内吞功能外，低密度脂蛋白受体相关蛋白 1 (LRP1) 还有助于细胞信号转导事件。在当前的研究中，研究了LRP1调节血小板衍生生长因子（PDGF）信号通路的潜力。 PDGF 是细胞迁移和增殖的关键调节因子，介导 LRP1 在其胞质域内的酪氨酸磷酸化。在 WI-38 成纤维细胞中，PDGF 介导的 LRP1 酪氨酸磷酸化发生在 37°C，但不在 4°C，此时内吞作用最小化。此外，用动力抑制剂 dynasore 阻断内吞作用也可以阻止 PDGF 介导的 LRP1 酪氨酸磷酸化。免疫荧光研究揭示了PDGF处理后LRP1与PDGF受体共定位于内体区室中，而表面生物素化实验证实磷酸化的LRP1主要源自细胞内区室。这些数据共同揭示了这两种受体在内体区室中的关联，它们在那里形成信号复合物。为了研究 LRP1 对 PDGF 信号传导的贡献，我们使用了 LRP1 遗传缺陷的小鼠胚胎成纤维细胞，并通过进行磷酸位点分析来鉴定这些细胞系响应 PDGF 刺激的表型变化。在分析的 38 种磷酸化蛋白中，有 8 种在 LRP1 缺陷的成纤维细胞中存在显着差异，并且当 LRP1 在这些细胞中重新表达时恢复。重要的是，结果表明 LRP1 表达对于 PDGF 介导的 ERK 激活是必需的。总体而言，研究表明 LRP1 与内体区室中的 PDGF 受体相关，并调节其信号传导特性，从而影响 MAPK 和 Akt/磷脂酰肌醇 3 激酶通路。
In addition to its endocytic function, the low density lipoprotein receptor-related protein 1 (LRP1) also contributes to cell signaling events. In the current study, the potential of LRP1 to modulate the platelet-derived growth factor (PDGF) signaling pathway was investigated. PDGF is a key regulator of cell migration and proliferation and mediates the tyrosine phosphorylation of LRP1 within its cytoplasmic domain. In WI-38 fibroblasts, PDGF-mediated LRP1 tyrosine phosphorylation occurred at 37 C but not at 4 C, where endocytosis is minimized. Furthermore, blockade of endocytosis with the dynamin inhibitor, dynasore, also prevented PDGF-mediated LRP1 tyrosine phosphorylation. Immunofluorescence studies revealed co-localization of LRP1 with the PDGF receptor after PDGF treatment within endosomal compartments, whereas surface biotinylation experiments confirmed that phosphorylated LRP1 primarily originates from intracellular compartments. Together, the data reveal the association of these two receptors in endosomal compartments where they form a signaling complex. To study the contribution of LRP1 to PDGF signaling, we used mouse embryonic fibroblasts genetically deficient in LRP1 and identified phenotypic changes in these cell lines in response to PDGF stimulation by performing phospho-site profiling. Of 38 phosphorylated proteins analyzed, 8 were significantly different in LRP1 deficient fibroblasts and were restored when LRP1 was expressed back in these cells. Importantly, the results revealed that LRP1 expression is necessary for PDGF-mediated activation of ERK. Overall, the studies reveal that LRP1 associates with the PDGF receptor in endosomal compartments and modulates its signaling properties affecting the MAPK and Akt/phosphatidylinositol 3-kinase pathways.