Department of Molecular Medicine, Graduate School of Pharmaceutical Sciences, Global COE Cell Fate Regulation Research and Education Unit, Kumamoto University, 5-1 Oe-Honmachi, Kumamoto 862-0973, Japan.
Biochem Biophys Res Commun. 2011 Jan 21;404(3):853-8. doi: 10.1016/j.bbrc.2010.12.074. Epub 2010 Dec 22.
Human breast cancer resistance protein (BCRP)/MXR/ABCG2 is a well-recognized ABC half-transporter that is highly expressed at the apical membrane of many normal tissues and cancer cells. BCRP facilitates disposition of endogenous and exogenous harmful xenobiotics to protect cells/tissues from xenobiotic-induced toxicity. Despite the enormous impact of BCRP in the physiological and pathophysiological regulation of the transport of a wide variety of substrates, little is known about the factors that regulate posttranslational expression of BCRP. Here, we identified Derlin-1, a member of a family of proteins that bears homology to yeast Der1p, as a posttranslational regulator of BCRP expression. Overexpression of Derlin-1 suppressed ER to Golgi transport of wild-type (WT) BCRP that is known to be efficiently trafficked to the plasma membrane. On the other hand, protein expression of N596Q variant of BCRP, N-linked glycosylation-deficient mutant that preferentially undergoes ubiquitin-mediated ER-associated degradation (ERAD), was strongly suppressed by the overexpression of Derlin-1, whereas knockdown of Derlin-1 stabilized N596Q protein, suggesting a negative regulatory role of Derlin-1 for N596Q protein expression. Notably, knockdown of Derlin-1 also stabilized the expression of tunicamycin-induced deglycosylated WT BCRP protein, implying the importance of glycosylation state for the recognition of BCRP by Derlin-1. Thus, our data demonstrate that Derlin-1 is a negative regulator for both glycosylated and non-glycosylated BCRP expression and provide a novel posttranslational regulatory mechanism of BCRP by Derlin-1.
人乳腺癌耐药蛋白（BCRP）/MXR/ABCG2 是一种公认的 ABC 半转运体，在许多正常组织和癌细胞的顶膜上高度表达。BCRP 促进内源性和外源性有害异生物质的处置，以保护细胞/组织免受异生物质诱导的毒性。尽管 BCRP 在广泛的底物的生理和病理生理学调节中的作用巨大，但对于调节 BCRP 翻译后表达的因素知之甚少。在这里，我们鉴定出 Derlin-1，一种与酵母 Der1p 同源的蛋白家族成员，是 BCRP 表达的翻译后调节剂。Derlin-1 的过表达抑制了已知被有效转运到质膜的野生型（WT）BCRP 的 ER 到高尔基体的转运。另一方面，N596Q 变异型 BCRP 的蛋白表达，即优先经历泛素介导的内质网相关降解（ERAD）的 N 连接糖基化缺陷突变体，被 Derlin-1 的过表达强烈抑制，而 Derlin-1 的敲低稳定了 N596Q 蛋白，表明 Derlin-1 对 N596Q 蛋白表达具有负调节作用。值得注意的是，Derlin-1 的敲低也稳定了衣霉素诱导的去糖基化 WT BCRP 蛋白的表达，这意味着糖基化状态对 Derlin-1 识别 BCRP 的重要性。因此，我们的数据表明 Derlin-1 是糖基化和非糖基化 BCRP 表达的负调节剂，并提供了 Derlin-1 对 BCRP 进行翻译后调节的新机制。
