A Phosphatidic Acid (PA) conveyor system of continuous intracellular transport from cell membrane to nucleus maintains EGF receptor homeostasis
A Phosphatidic Acid (PA) conveyor system of continuous intracellular transport from cell membrane to nucleus maintains EGF receptor homeostasis
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DOI：
10.18632/oncotarget.9685
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发表时间：
2016-07-26
期刊：
影响因子：
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通讯作者：
Gomez-Cambronero, Julian
中科院分区：
文献类型：
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作者：
Henkels, Karen M.;Miller, Taylor E.;Gomez-Cambronero, Julian
细胞内有丝分裂原磷脂酸（PA）的浓度必须维持在低水平，直到需要细胞增殖。PA的时空运输如何影响其在不同细胞区室中的靶蛋白尚不完全清楚。我们报道，在癌细胞中，PA从细胞膜到细胞核来回循环，影响表皮生长因子（EGF）的功能，这一过程涉及PPARa/LXRa信号传导。在与其配体结合后，EGF受体（EGFR）启动的磷脂酶D （PLD）激活导致细胞内PA产生的峰值，形成囊泡，从早期内体（EEA1标记）运输EGFR，并在晚期内体和高尔基体（RCAS标记）中延长内化。用荧光标记PA （NBD-PA）孵育的细胞显示PA在细胞质中的“弥漫性”位置，与EGFR共定位的小点（0.5 μ m）囊泡。我们还报道了PPARa/LXRa形成异源二聚体，与EGFR启动子中的新响应元件（RE）结合。核PA增强EGFR表达，其作用与磷脂的有丝分裂能力相容。新生成的EGFR被包装到PA循环囊泡（Rab11标记物）中，运输回细胞质和质膜。然而，PLD+PA组合阻碍了PPARa/LXRa与EGFR启动子的结合。因此，如果细胞核内的PA水平达到一定的阈值（bbb100 nM）， PA就会超过核受体的竞争，转录就会受到抑制。PLD-PA这种靶向EGFR运输并双相调节其转录的新信号功能可以解释癌细胞中细胞增殖的启动和维持。
The intracellular concentration of the mitogen phosphatidic acid (PA) must be maintained at low levels until the need arises for cell proliferation. How temporal and spatial trafficking of PA affects its target proteins in the different cellular compartments is not fully understood. We report that in cancer cells, PA cycles back and forth from the cellular membrane to the nucleus, affecting the function of epidermal growth factor (EGF), in a process that involves PPARa/LXRa signaling. Upon binding to its ligand, EGF receptor (EGFR)-initiated activation of phospholipase D (PLD) causes a spike in intracellular PA production that forms vesicles transporting EGFR from early endosomes (EEA1 marker) and prolonged internalization in late endosomes and Golgi (RCAS marker). Cells incubated with fluorescent-labeled PA (NBD-PA) show PA in "diffuse" locations throughout the cytoplasm, punctae (small, 0.5 mu m) vesicles that co-localize with EGFR. We also report that PPARa/LXRa form heterodimers that bind to new Responsive Elements (RE) in the EGFR promoter. Nuclear PA enhances EGFR expression, a role compatible with the mitogenic ability of the phospholipid. Newly made EGFR is packaged into PA recycling vesicles (Rab11 marker) and transported back to the cytoplasm and plasma membrane. However, a PLD+PA combination impedes binding of PPARa/LXRa to the EGFR promoter. Thus, if PA levels inside the nucleus reach a certain threshold (>100 nM) PA outcompetes the nuclear receptors and transcription is inhibited. This new signaling function of PLD-PA targeting EGFR trafficking and biphasically modulating its transcription, could explain cell proliferation initiation and its maintenance in cancer cells.