Endoplasmic reticulum (ER) membrane proteins (LUNAPARKs) are required for proper configuration of the cortical ER network in plant cells
Endoplasmic reticulum (ER) membrane proteins (LUNAPARKs) are required for proper configuration of the cortical ER network in plant cells
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植物细胞中皮质 ER 网络的正确配置需要内质网 (ER) 膜蛋白 (LUNAPARK)
DOI：
10.1093/pcp/pcy137
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发表时间：
2018
影响因子：
4.9
通讯作者：
and I. Hara-Nishimura
中科院分区：
文献类型：
--
作者：
H. Ueda;N. Ohta;Y. Kimori;T. Uchida;T. Shimada;Kentaro Tamura;and I. Hara-Nishimura
内质网（ER）是由膜池和小管组成的大型网状结构，在细胞内膜脂双层中占很大比例。在哺乳动物和酵母中，LUNAPARK蛋白优先定位于ER网络的三通连接处，稳定连接并建立ER结构。我们鉴定了两个拟南芥同源物，并将它们命名为LNPA和LNPB。亚细胞定位分析与非二聚型的绿色荧光蛋白（GFP）显示，LNPA和LNPB主要分布在整个ER，但不优先定位在三通路口。定量分析表明，LNPA和LNPB的缺乏导致皮质ER池发育不良，内质网密度降低。这些表型与酵母和哺乳动物的LNP缺陷突变体相反。尽管半胱氨酸残基在酵母LNP同源物（Lnp1p）的锌指基序中的重要性，但LNPA的相应半胱氨酸残基对于ER形态的稳定不是必需的，因为用丙氨酸残基取代LNPA蛋白的锌指基序中的四个半胱氨酸残基并不影响其功能。一个重要的表型是从ER产生大的球形结构。结构的形成可能减少用于产生网络的ER膜的量，导致ER网络的发育不良。总之，我们的研究结果表明，植物LNP的功能与酵母和哺乳动物中的LNP不同：它们的功能是在整个细胞中适当地分布ER膜。
The endoplasmic reticulum (ER) is a large network made of membranous cisternae and tubules, which accounts for a large proportion of the total lipid bilayer endomembrane of the cell. In mammals and yeast, LUNAPARK proteins are preferentially localized at the three-way junctions of the ER network, stabilizing the junctions and establishing the ER architecture. We identified two Arabidopsis homologs and designated them LNPA and LNPB. Subcellular localization analysis with a non-dimerizable type of green fluorescent protein (GFP) revealed that both LNPA and LNPB are predominantly distributed throughout the ER, but not preferentially localized at the three-way junctions. Quantitative analysis of the network in the double mutantlnpa lnpbrevealed that deficiency of LNPA and LNPB caused the cortical ER to develop poor ER cisternae and a less dense tubular network. These phenotypes are opposite to those ofLNP-deficient mutants of yeast and mammals. Despite the importance of cysteine residues in the zinc finger motif of the yeast LNP homolog (Lnp1p), the corresponding cysteine residues of LNPA were not necessary for the stabilization of ER morphology because replacing the four cysteine residues in the zinc finger motif of the LNPA protein with alanine residues did not affect its function. A significant phenotype oflnpa lnpbis generation of large spherical structures from the ER. Formation of the structures might reduce the amounts of the ER membrane to be used for generating the network, resulting in poor development of the ER network. Taken together, our results suggest that plant LNPs function differently from those in yeast and mammals: they function to distribute ER membranes appropriately throughout the cells.