Sialylation of EGFR by ST6GAL1 induces receptor activation and modulates trafficking dynamics.

The Journal of Biological Chemistry Pub Date : 2023-10-01 Epub Date: 2023-09-01 DOI:10.1016/j.jbc.2023.105217
Katherine E Ankenbauer, Tejeshwar C Rao, Alexa L Mattheyses, Susan L Bellis
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Abstract

Aberrant glycosylation is a hallmark of a cancer cell. One prevalent alteration is an enrichment in α2,6-linked sialylation of N-glycosylated proteins, a modification directed by the ST6GAL1 sialyltransferase. ST6GAL1 is upregulated in many malignancies including ovarian cancer. Prior studies have shown that the addition of α2,6 sialic acid to the epidermal growth factor receptor (EGFR) activates this receptor, although the mechanism was largely unknown. To investigate the role of ST6GAL1 in EGFR activation, ST6GAL1 was overexpressed in the OV4 ovarian cancer line, which lacks endogenous ST6GAL1, or knocked-down in the OVCAR-3 and OVCAR-5 ovarian cancer lines, which have robust ST6GAL1 expression. Cells with high expression of ST6GAL1 displayed increased activation of EGFR and its downstream signaling targets, AKT and NFκB. Using biochemical and microscopy approaches, including total internal reflection fluorescence microscopy, we determined that the α2,6 sialylation of EGFR promoted its dimerization and higher order oligomerization. Additionally, ST6GAL1 activity was found to modulate EGFR trafficking dynamics following EGF-induced receptor activation. Specifically, EGFR sialylation enhanced receptor recycling to the cell surface following activation while simultaneously inhibiting lysosomal degradation. 3D widefield deconvolution microscopy confirmed that in cells with high ST6GAL1 expression, EGFR exhibited greater colocalization with Rab11 recycling endosomes and reduced colocalization with LAMP1-positive lysosomes. Collectively, our findings highlight a novel mechanism by which α2,6 sialylation promotes EGFR signaling by facilitating receptor oligomerization and recycling.

ST6GAL1对EGFR的唾液酸化诱导受体活化并调节运输动力学。
异常糖基化是癌症细胞的标志。一个普遍的变化是N-糖基化蛋白的α2,6-连接唾液酸化的富集,这是由ST6GAL1唾液酸转移酶指导的修饰。ST6GAL1在许多恶性肿瘤中上调,包括卵巢癌症。先前的研究表明,在表皮生长因子受体(EGFR)中添加α2,6唾液酸会激活该受体,尽管其机制在很大程度上尚不清楚。为了研究ST6GAL1在EGFR激活中的作用,ST6GAL 1在缺乏内源性ST6GALl的OV4卵巢癌症系中过表达,或在具有强大ST6GAL1表达的OVCAR-3和OVCAR-5卵巢癌症系中敲低。ST6GAL1高表达的细胞显示出EGFR及其下游信号靶点AKT和NFκB的激活增加。使用生物化学和显微镜方法,包括全内反射荧光显微镜,我们确定EGFR的α2,6唾液酸化促进了其二聚化和更高阶低聚。此外,发现ST6GAL1活性在EGF诱导的受体激活后调节EGFR运输动力学。具体而言,EGFR唾液酸化增强受体在激活后再循环到细胞表面,同时抑制溶酶体降解。3D宽场去卷积显微镜证实,在ST6GAL1高表达的细胞中,EGFR与Rab11循环内体的共定位更强,与LAMP1阳性溶酶体的共定位减少。总之,我们的研究结果强调了一种新的机制,通过该机制,α2,6唾液酸化通过促进受体寡聚和再循环来促进EGFR信号传导。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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