Surfactant protein A down-regulates epidermal growth factor receptor by mechanisms different from those of surfactant protein D
Surfactant protein A down-regulates epidermal growth factor receptor by mechanisms different from those of surfactant protein D
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DOI：
10.1074/jbc.m117.800771
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发表时间：
2017-11-10
影响因子：
4.8
通讯作者：
Kuroki, Yoshio
中科院分区：
文献类型：
--
作者：
Hasegawa, Yoshihiro;Takahashi, Motoko;Kuroki, Yoshio
我们最近报道了凝集素表面活性剂蛋白D （SP-D）通过SP-D的碳水化合物识别结构域（CRD）和EGFR的n -聚糖之间的相互作用，通过干扰与EGFR结合的配体来抑制表皮生长因子受体（EGFR）信号传导。在这里，我们报道了表面活性剂蛋白A （SP-A）也抑制A549人肺腺癌细胞和稳定表达人EGFR的CHOK1细胞中的EGF信号传导，并且SP-A抑制A549细胞的增殖和运动。I-125-EGF的结果表明SP-A干扰EGF与EGFR的结合，配体印迹分析表明SP-A在A549细胞中与EGFR结合。我们还发现SP-A直接结合EGFR的重组细胞外结构域（可溶性EGFR或sEGFR），与SP-D不同，这种结合不会被EDTA、过量甘露糖或肽：n -糖苷酶F处理阻断。我们制备了SP-A的抗胶原酶片段（CRF），由CRD和SP-A的颈部结构域组成，观察到CRF直接结合sEGFR，但不抑制egf诱导的EGFR磷酸化或A549细胞的增殖。这些结果表明，SP-A通过抑制配体与EGFR和SP-D的结合，从而结合EGFR并下调EGF信号。然而，与SP-D不同的是，SP-A凝集素活性和EGFR n -聚糖不参与SP-A和EGFR的相互作用。此外，我们的研究结果表明，SP-A的寡聚化是抑制SP-A对EGF信号传导的作用所必需的。
We recently reported that the lectin surfactant protein D (SP-D) suppresses epidermal growth factor receptor (EGFR) signaling by interfering with ligand binding to EGFR through an interaction between the carbohydrate-recognition domain (CRD) of SP-D and N-glycans of EGFR. Here, we report that surfactant protein A (SP-A) also suppresses EGF signaling in A549 human lung adenocarcinoma cells and in CHOK1 cells stably expressing human EGFR and that SP-A inhibits the proliferation and motility of the A549 cells. Results with I-125-EGF indicated that SP-A interferes with EGF binding to EGFR, and a ligand blot analysis suggested that SP-A binds EGFR in A549 cells. We also found that SP-A directly binds the recombinant extracellular domain of EGFR (soluble EGFR or sEGFR), and this binding, unlike that of SP-D, was not blocked by EDTA, excess mannose, or peptide:N-glycosidase F treatment. We prepared a collagenase-resistant fragment (CRF) of SP-A, consisting of CRD plus the neck domain of SP-A, and observed that CRF directly binds sEGFR but does not suppress EGF-induced phosphorylation of EGFR in or proliferation of A549 cells. These results indicated that SP-A binds EGFR and down-regulates EGF signaling by inhibiting ligand binding to EGFR as well as SP-D. However, unlike for SP-D, SP-A lectin activity and EGFR N-glycans were not involved in the interaction between SP-A and EGFR. Furthermore, our results suggested that oligomerization of SP-A is necessary to suppress the effects of SP-A on EGF signaling.