|
RHD3(ROOT HAIR DEFECTIVE3，根毛缺陷3)是参与内质网形成过程中内质网同型融合的细胞质 GTPase。由于内质网小管过度融合将导致片状内质网的形成，因此必须严格调控地膜蛋白 g/pases 的作用。 我们在这里表明，RHD3在内质网的三向连接处，即不同的内质网小管融合的位点，有两个拟南芥 LUNAPARK 蛋白(LNP1和 LNP2)的相互作用。由 RHD3招募到新形成的3-way连接，LNPs 与 RHD3负作用，以稳定初期的3路连接的 ER。 如果没有这种 lnp 介导的稳定化，在拟南芥 lnp1-1 lnp2-1突变细胞中，ER 就会变成一个致密的管状网络。有趣的是，在 lnp1-1lnp2-1突变细胞中，RHD3水平高于野生型植物。 RHD3在无 lnp 存在时降解较慢，在 MG132和 Concanamycin a 存在时降解较慢，但在 lnp 存在时，RHD3的降解较快。我们已经提供了体外实验证据，证明拟南芥 LNPs 具有 E3泛素连接酶活性，并且 LNP1可以直接泛素化 RHD3。 我们的数据表明，当内质网融合完成后，lnp 会降解 RHD3，使初生的三向连接稳定下来，并维持管状的内质网。 Abstract: RHD3 (ROOT HAIR DEFECTIVE3) is an atlastin GTPase involved in homotypic fusion of ER tubules in the formation of the interconnected ER network. Because excessive fusion of ER tubules will lead to the formation of sheet-like ER, the action of atlastin GTPases must be tightly regulated. We show here that RHD3 physically interacts with two Arabidopsis LUNAPARK proteins (LNP1 and LNP2) at 3-way junctions of the ER, the sites where different ER tubules fuse. Recruited by RHD3 to newly formed 3-way junctions, LNPs act negatively with RHD3 to stabilize the nascent 3-way junctions of the ER. Without this LNP-mediated stabilization, in Arabidopsis lnp1-1 lnp2-1 mutant cells, the ER becomes a dense tubular network. Interestingly, in lnp1-1 lnp2-1 mutant cells, the RHD3 level is higher than that in wild type plants. RHD3 is degraded more slowly in the absence of LNPs, as well as in the presence of MG132 and Concanamycin A. However, in the presence of LNPs, the degradation of RHD3 is promoted. We have provided an in vitro evidence that Arabidopsis LNPs have E3 ubiquitin ligase activity and that LNP1 can directly ubiquitinates RHD3. Our data show that after ER fusion is completed, RHD3 is degraded by LNPs so that nascent 3-way junctions can be stabilized and a tubular ER network can be maintained. 版权作品，未经PaperRSS书面授权，严禁转载，违者将被追究法律责任。 PaperRSS，关注生命科学，高校院所科研进展。
|
