The protein O-glucosyltransferase Rumi modifies eyes shut to promote rhabdomere separation in Drosophila.
The protein O-glucosyltransferase Rumi modifies eyes shut to promote rhabdomere separation in Drosophila.
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DOI：
10.1371/journal.pgen.1004795
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发表时间：
2014-11
期刊：
影响因子：
4.5
通讯作者：
Jafar-Nejad H
中科院分区：
文献类型：
--
作者：
Haltom AR;Lee TV;Harvey BM;Leonardi J;Chen YJ;Hong Y;Haltiwanger RS;Jafar-Nejad H
蛋白O-葡萄糖基转移酶RUMI/POGLUT1通过将O-葡萄糖残基添加到Notch胞外区来调节果蝇Notch信号转导。鲁米还有其他预测的靶点，包括Crumbs(CRB)和Eys(Eys)，这两个都参与光感受器的发育。然而，Rumi是否是CRB和Eys功能所必需的仍不清楚。在这里，我们报告，在没有Rumi或其酶活性的情况下，每个小眼内的几个横纹体不能以Notch独立的方式彼此分离。质谱分析表明，在CRB和EYS上存在O-葡萄糖。然而，突变CRB敲入等位基因中的所有O-糖基化位点并不会导致横纹附着，从而排除了CRB在这一过程中作为生物相关的RUMI靶点的可能性。相反，EYS和RUMI表现出剂量敏感的遗传交互作用。此外，虽然在野生型小眼中，大部分Eys蛋白存在于横纹间间隙(IRS)，但在鲁米突变体中，有相当一部分EYS保留在感光细胞中。在较高温度下，RUMI突变体的胞内EYs积累和IRS缺陷恶化，并伴随着EYS总水平的∼下降50%。此外，移除内质网伴侣的一个拷贝会增强鲁米突变动物的横纹肌附着。综上所述，我们的数据表明，Rumi对EYS的O-糖基化通过促进EYS的正确折叠和在中蛹阶段的关键时间窗口中的稳定性来确保横纹肌的分离。在常染色体隐性视网膜色素变性患者中突变的人眼也含有多个RUMI靶点。因此，O-葡萄糖对EYS的调节作用可能是保守的。糖基化(将糖加到蛋白质和其他有机分子上)对蛋白质功能和动物发育很重要。每种形式的糖基化通常存在于多种蛋白质上。因此，理解糖在动物发育中的作用的一个主要挑战是确定哪种蛋白质(S)被特定的糖修饰需要糖修饰以实现适当的功能。我们之前已经证明，一种名为RUMI的酶将葡萄糖分子添加到重要的细胞表面受体Notch上，并且葡萄糖在果蝇和哺乳动物的Notch功能中都发挥着关键作用。利用果蝇，我们现在已经确定了一个新的RUMI靶标，称为“眼睛关闭”，这是一种分泌的蛋白质，在果蝇眼睛中邻近光感受器的光学隔离中起着关键作用。我们的数据表明，闭上眼睛的葡萄糖分子在眼睛发育的关键时间窗内促进其折叠和稳定。人类闭上眼睛的突变会导致一种毁灭性的视网膜退化和视力丧失。由于人类闭上眼睛也被预测含有葡萄糖分子，我们的工作提供了一个框架，以探索糖修饰在人类疾病蛋白质生物学中的作用。
The protein O-glucosyltransferase Rumi/POGLUT1 regulates Drosophila Notch signaling by adding O-glucose residues to the Notch extracellular domain. Rumi has other predicted targets including Crumbs (Crb) and Eyes shut (Eys), both of which are involved in photoreceptor development. However, whether Rumi is required for the function of Crb and Eys remains unknown. Here we report that in the absence of Rumi or its enzymatic activity, several rhabdomeres in each ommatidium fail to separate from one another in a Notch-independent manner. Mass spectral analysis indicates the presence of O-glucose on Crb and Eys. However, mutating all O-glucosylation sites in a crb knock-in allele does not cause rhabdomere attachment, ruling out Crb as a biologically-relevant Rumi target in this process. In contrast, eys and rumi exhibit a dosage-sensitive genetic interaction. In addition, although in wild-type ommatidia most of the Eys protein is found in the inter-rhabdomeral space (IRS), in rumi mutants a significant fraction of Eys remains in the photoreceptor cells. The intracellular accumulation of Eys and the IRS defect worsen in rumi mutants raised at a higher temperature, and are accompanied by a ∼50% decrease in the total level of Eys. Moreover, removing one copy of an endoplasmic reticulum chaperone enhances the rhabdomere attachment in rumi mutant animals. Altogether, our data suggest that O-glucosylation of Eys by Rumi ensures rhabdomere separation by promoting proper Eys folding and stability in a critical time window during the mid-pupal stage. Human EYS, which is mutated in patients with autosomal recessive retinitis pigmentosa, also harbors multiple Rumi target sites. Therefore, the role of O-glucose in regulating Eys may be conserved. Glycosylation (addition of sugars to proteins and other organic molecules) is important for protein function and animal development. Each form of glycosylation is usually present on multiple proteins. Therefore, a major challenge in understanding the role of sugars in animal development is to identify which protein(s) modified by a specific sugar require the sugar modification for proper functionality. We have previously shown that an enzyme called Rumi adds glucose molecules to an important cell surface receptor called Notch, and that glucose plays a key role in the function of Notch both in fruit flies and in mammals. Using fruit flies, we have now identified a new Rumi target called “Eyes shut”, a secreted protein with a critical role in the optical isolation of neighboring photoreceptors in the fly eye. Our data suggest that glucose molecules on Eyes shut promote its folding and stability in a critical time window during eye development. Mutations in human Eyes shut result in a devastating form of retinal degeneration and loss of vision. Since human Eyes shut is also predicted to harbor glucose molecules, our work provides a framework to explore the role of sugar modifications in the biology of a human disease protein.
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影响因子：
64.5
作者：
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通讯作者：
Mann, RS
影响因子：
3.9
作者：
Audo, Isabelle;Sahel, Jose-Alain;Zeitz, Christina
通讯作者：
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作者：
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影响因子：
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作者：
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通讯作者：
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DOI：
10.1073/pnas.1004060107
发表时间：
2010-09-07
影响因子：
11.1
作者：
Chen, Chiao-Lin;Gajewski, Kathleen M.;Halder, Georg
通讯作者：
Halder, Georg