Minich Rebecca R, Li Jin, Tempel Bruce L
Department of Pharmacology, School of Medicine, University of Washington, Seattle, WA, 98195, USA.
Department of Otolaryngology-HNS, School of Medicine, University of Washington, Box 357923, Seattle, WA, 98195, USA.
BMC Mol Biol. 2017 May 22;18(1):14. doi: 10.1186/s12867-017-0092-1.
Along with sodium/calcium (Ca) exchangers, plasma membrane Ca ATPases (ATP2Bs) are main regulators of intracellular Ca levels. There are four ATP2B paralogs encoded by four different genes. Atp2b2 encodes the protein pump with the fastest activation, ATP2B2. In mice, the Atp2b2 transcript has several alternate transcriptional start site variants: α, β, µ and δ. These variants are expressed in developmental and tissue specific manners. The α and β Atp2b2 transcripts are equally expressed in the brain. αAtp2b2 is the only transcript found in the outer hair cells of young mice (Silverstein RS, Tempel BL. in Neuroscience 141:245-257, 2006). Mutations in the coding region of the mouse Atp2b2 gene indicate a narrow window for tolerated dysfunction of the ATP2B2 protein, specifically in the auditory system. This highlights the necessity of tight regulation of this gene for normal cell physiology.
Although ATP2Bs are important regulators of Ca in many cell types, little is known about their transcriptional regulation. This study identifies the proximal promoter of the αAtp2b2 transcript. Further investigations indicate that ATOH1 and EGR1 modulate promoter activity. Additionally, we report that EGR1 increases endogenous expression of Atp2b2 transcript in two cell lines. Electrophoretic mobility shift assays (EMSA) indicate that EGR1 binds to a specific site in the CpG island of the αAtp2b2 promoter.
This study furthers our understanding of Atp2b2 regulation by: (I) elucidating transcriptional regulatory mechanisms for Atp2b2, and (II) identifying transcription factors that modulate expression of Atp2b2 in the brain and peripheral auditory system and (III) allows for future studies modulating gene expression of Atp2b2.
与钠/钙（Ca）交换体一样，质膜Ca ATP酶（ATP2B）是细胞内Ca水平的主要调节因子。有四个由不同基因编码的ATP2B旁系同源物。Atp2b2编码激活速度最快的蛋白泵ATP2B2。在小鼠中，Atp2b2转录本有几种不同的转录起始位点变体：α、β、µ和δ。这些变体以发育和组织特异性方式表达。α和β Atp2b2转录本在大脑中表达量相当。αAtp2b2是在幼鼠外毛细胞中发现的唯一转录本（Silverstein RS，Tempel BL。《神经科学》141：245 - 257，2006）。小鼠Atp2b2基因编码区的突变表明ATP2B2蛋白功能障碍的耐受窗口很窄，特别是在听觉系统中。这突出了对该基因进行严格调控以维持正常细胞生理功能的必要性。
尽管ATP2B在许多细胞类型中是Ca的重要调节因子，但其转录调控知之甚少。本研究确定了αAtp2b2转录本的近端启动子。进一步研究表明，ATOH1和EGR1调节启动子活性。此外，我们报告EGR1增加了两个细胞系中Atp2b2转录本的内源性表达。电泳迁移率变动分析（EMSA）表明EGR1与αAtp2b2启动子CpG岛中的一个特定位点结合。
本研究通过以下方式加深了我们对Atp2b2调控的理解：（I）阐明Atp2b2的转录调控机制，（II）鉴定调节大脑和外周听觉系统中Atp2b2表达的转录因子，以及（III）为未来调节Atp2b2基因表达的研究提供了可能。
