Genetic and Structural Analysis of Hmg2p-induced Endoplasmic Reticulum Remodeling in Saccharomyces cerevisiae
Genetic and Structural Analysis of Hmg2p-induced Endoplasmic Reticulum Remodeling in Saccharomyces cerevisiae
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DOI：
10.1091/mbc.e07-11-1188
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发表时间：
2008-10-01
影响因子：
3.3
通讯作者：
Hampton, Randolph Y.
中科院分区：
文献类型：
--
作者：
Federovitch, Christine M.;Jones, Ying Z.;Hampton, Randolph Y.
内质网 (ER) 具有高度可塑性，并且增加不同的单一 ER 驻留膜蛋白（例如 HMG-CoA 还原酶 (HMGR)）的表达，可以诱导 ER 膜发生戏剧性的重组，形成高度组织化的阵列。对两种酵母 HMGR 同工酶 Hmg1p 和 Hmg2p 的 ER 重塑行为的研究表明，它们在机制上可能是不同的。我们检查了 Hmg2p 生成其特征结构所需的特征，发现其分子要求与 Hmg1p 相似。然而，Hmg1p 和 Hmg2p 生成的结构具有由蛋白质的跨膜区域决定的独特细胞生物学特征。与此同时，我们进行了遗传筛选来鉴定 HER 基因（Hmg2p 诱导的 ER 重塑所需），进一步证实这两种蛋白的膜重组机制是不同的，因为大多数 HER 基因是 Hmg2p 所需的，而不是 Hmg1p 诱导的 ER 重塑所需的。鉴定出的 HER 基因之一是 PSD1，它编码磷脂生物合成酶磷脂酰丝氨酸脱羧酶。这种与磷脂生物合成的直接联系促使人们更详细地研究 Hmg2p 对磷脂突变体和组成的影响。我们的分析表明，Hmg2p 的过度表达导致包括 Psd1p 酶在内的磷脂酰胆碱生物合成甲基化途径缺失中显着且特异性的生长缺陷。此外，Hmg2p 表达的增加以暗示 PSD1 的作用的方式改变了细胞磷脂的组成。与 Hmg2p 诱导的 ER 重塑不同，这些磷脂效应需要 Hmg2p 的酶活性。总之，我们的结果表明，虽然相关，但 Hmg2p 和 Hmg1p 诱导的 ER 重塑在机制上是不同的。
The endoplasmic reticulum (ER) is highly plastic, and increased expression of distinct single ER-resident membrane proteins, such as HMG-CoA reductase (HMGR), can induce a dramatic restructuring of ER membranes into highly organized arrays. Studies on the ER-remodeling behavior of the two yeast HMGR isozymes, Hmg1p and Hmg2p, suggest that they could be mechanistically distinct. We examined the features of Hmg2p required to generate its characteristic structures, and we found that the molecular requirements are similar to those of Hmg1p. However, the structures generated by Hmg1p and Hmg2p have distinct cell biological features determined by the transmembrane regions of the proteins. In parallel, we conducted a genetic screen to identify HER genes (required for Hmg2p-induced ER Remodeling), further confirming that the mechanisms of membrane reorganization by these two proteins are distinct because most of the HER genes were required for Hmg2p but not Hmg1p-induced ER remodeling. One of the HER genes identified was PSD1, which encodes the phospholipid biosynthetic enzyme phosphatidylserine decarboxylase. This direct connection to phospholipid biosynthesis prompted a more detailed examination of the effects of Hmg2p on phospholipid mutants and composition. Our analysis revealed that overexpression of Hmg2p caused significant and specific growth defects in nulls of the methylation pathway for phosphatidylcholine biosynthesis that includes the Psd1p enzyme. Furthermore, increased expression of Hmg2p altered the composition of cellular phospholipids in a manner that implied a role for PSD1. These phospholipid effects, unlike Hmg2p-induced ER remodeling, required the enzymatic activity of Hmg2p. Together, our results indicate that, although related, Hmg2p- and Hmg1p-induced ER remodeling are mechanistically distinct.