Lunapark ubiquitinates atlastin-2 for the tubular network formation of the endoplasmic reticulum
Lunapark ubiquitinates atlastin-2 for the tubular network formation of the endoplasmic reticulum
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DOI：
10.1093/jb/mvac060
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发表时间：
2022-07-26
影响因子：
2.7
通讯作者：
Sakisaka, Toshiaki
中科院分区：
文献类型：
--
作者：
Anggrandariyanny, Putri Chynthia;Kajiho, Hiroaki;Sakisaka, Toshiaki
内质网（内质网）小管通过三向连接相互连接，从而形成管状内质网。Lunapark （Lnp）定位并稳定三向结。Lnp的n端胞质结构域具有泛素连接酶活性。然而，Lnp泛素连接酶活性如何参与管状内质网形成的分子机制尚不清楚。在这项研究中，我们检测了负责形成管状内质网的内质网膜蛋白是否被Lnp泛素化。我们发现atlastin-2 （ATL2）是ATL家族的一种异构体，通过连接内质网小管介导三向连接的产生，是Lnp泛素化的一种新型底物。Lnp在三向交界处的定位对于ATL2的泛素化非常重要。赖氨酸56、57、282和302是Lnp潜在的泛素化位点。沉默ATL2减少了三向连接的数量，而在ATL2敲除的细胞中，赖氨酸残基被精氨酸取代的ATL2突变体的表达未能挽救三向连接的减少。这些结果表明Lnp泛素化ATL2在三向连接处，以形成适当的管状内质网。
Endoplasmic reticulum (ER) tubules are interconnected by three-way junctions, resulting in the formation of a tubular ER network. Lunapark (Lnp) localizes to and stabilizes the three-way junctions. The N-terminal cytoplasmic domain in Lnp has a ubiquitin ligase activity. However, the molecular mechanism of how the ubiquitin ligase activity of Lnp is involved in the formation of the tubular ER network remains unknown. In this study, we examined whether the ER membrane proteins responsible for the formation of the tubular ER network are ubiquitinated by Lnp. We found that atlastin-2 (ATL2), an isoform of the ATL family mediating the generation of the three-way junctions by connecting the ER tubules, is a novel substrate for ubiquitination by Lnp. The localization of Lnp at the three-way junctions is important for ubiquitination of ATL2. Lysine 56, 57, 282 and 302 are the potential ubiquitination sites by Lnp. Silencing ATL2 decreased the number of the three-way junctions, and the expression of the ATL2 mutant in which the lysine residues are substituted with arginine failed to rescue the decrease of the three-way junctions in the ATL2 knocked-down cells. These results suggest that Lnp ubiquitinates ATL2 at the three-way junctions for the proper tubular ER network formation.