Negrón-Vega Lisandra, Cora Elsa M, Pérez-Torres Marianela, Tang Shou-Ching, Maihle Nita J, Ryu Jung Su
Department of Biochemistry, University of Puerto Rico-Medical Sciences Campus, PO Box 365067, San Juan, PR, 00936-5067, Puerto Rico.
School of Pharmacy, University of Puerto Rico-Medical Sciences Campus, PO Box 365067, San Juan, PR, 00936-5067, Puerto Rico.
Biochem Biophys Rep. 2022 Aug 19;31:101326. doi: 10.1016/j.bbrep.2022.101326. eCollection 2022 Sep.
Human epidermal growth factor receptor isoform D (EGFR; isoform D) is a soluble protein from a 3 kb alternate mRNA transcript that arises from the human EGFR gene. Several studies have identified this circulating isoform of EGFR as a potential diagnostic biomarker for the detection of early stage of cancers. While the expression of the full-length EGFR (isoform A) is regulated by its cognate ligand, EGF, as well as by phorbol myristate acetate (PMA), no studies have examined the factors regulating the expression of EGFR isoform D. In this study, using breast cancer cell lines, we show that the HER receptor ligands, EGF and neuregulin (NRG-1β), as well as the phorbol ester, PMA, can increase the expression of EGFR isoform D, as well as isoform A. Our results, based on measurement of mRNA levels, suggest that EGF induced expression of both isoform A and isoform D occur through a mitogen activated protein kinase (MAPK)-dependent mechanism, and also suggest that protein kinase C is involved in PMA-induced regulation of both isoforms. We also demonstrate that NRG-1β increases isoform A and isoform D expression via the MAPK-dependent pathway, but this regulation occurs independently of phosphatidylinositol 3-kinase/Akt activation. These results suggest that regulation of EGFR isoform A and isoform D expression occur using similar mechanisms. Despite commonalities in the transcriptional regulation of these two EGFR isoforms, the half-lives of these two transcripts is quite different. Moreover, EGFR isoform D, unlike isoform A, is not post-transcriptionally modulated by EGFR activators in the breast cancer cell line MDA-MB-468.
人表皮生长因子受体异构体D（EGFR；异构体D）是一种可溶性蛋白，来自人EGFR基因产生的3 kb可变mRNA转录本。多项研究已将这种循环的EGFR异构体鉴定为检测癌症早期阶段的潜在诊断生物标志物。虽然全长EGFR（异构体A）的表达受其同源配体表皮生长因子（EGF）以及佛波酯肉豆蔻酸乙酸酯（PMA）调控，但尚无研究探讨调控EGFR异构体D表达的因素。在本研究中，我们使用乳腺癌细胞系表明，HER受体配体EGF和神经调节蛋白（NRG-1β）以及佛波酯PMA均可增加EGFR异构体D以及异构体A的表达。我们基于mRNA水平测量的结果表明，EGF诱导的异构体A和异构体D的表达均通过丝裂原活化蛋白激酶（MAPK）依赖性机制发生，并且还表明蛋白激酶C参与PMA诱导的两种异构体的调控。我们还证明，NRG-1β通过MAPK依赖性途径增加异构体A和异构体D的表达，但这种调控独立于磷脂酰肌醇3激酶/蛋白激酶B（PI3K/Akt）激活发生。这些结果表明，EGFR异构体A和异构体D的表达调控机制相似。尽管这两种EGFR异构体在转录调控方面存在共性，但这两种转录本的半衰期却大不相同。此外，与异构体A不同，EGFR异构体D在乳腺癌细胞系MDA-MB-468中不受EGFR激活剂的转录后调节。
