The BTB-kelch protein LZTR-1 is a novel Golgi protein that is degraded upon induction of apoptosis
The BTB-kelch protein LZTR-1 is a novel Golgi protein that is degraded upon induction of apoptosis
复制标题
DOI：
10.1074/jbc.m509073200
复制
发表时间：
2006-02-24
影响因子：
4.8
通讯作者：
Kroll, J
中科院分区：
文献类型：
--
作者：
Nacak, TG;Leptien, K;Kroll, J
BTB-kelch超家族的成员在基本的细胞过程中发挥重要作用，如调节细胞形态、迁移和基因表达。BTB-kelch蛋白LZTR-1在大多数DiGeorge综合征患者中缺失，被认为是一种转录调节因子。然而，迄今为止尚未进行LZTR-1的功能和表达谱研究。因此，我们研究了LZTR-1的亚细胞定位和功能，以深入了解其生物学作用。蛋白质的一级结构分析揭示了LZTR-1内的6个N-末端kelch基序和C末端的2个BTB/POZ结构域。使用高尔基体标记物GM 130、Golgin-97和TGN 46对LZTR-1的亚细胞分布进行共聚焦分析，鉴定了LZTR-1仅定位于由其第二BTB/POZ结构域介导的高尔基体网络的细胞质表面上。与大多数其他BTB-kelch蛋白相比，LZTR-1不与肌动蛋白共定位。用布雷菲德菌素A处理并没有导致LZTR-1重新分布到内质网，而是导致其重新定位在分散的、间断的结构中，这些结构也对GM 130呈阳性。这些数据表明，LZTR-1是高尔基体基质相关蛋白。在诱导细胞凋亡后，LZTR-1在酪氨酸残基上磷酸化，随后降解;这可以通过加入半胱天冬酶抑制剂Z-VAD-fatase和蛋白酶体抑制剂lactacystin和MG 132部分挽救。总之，我们的实验确定LZTR-1作为第一个专门定位于高尔基体网络的BTB-kelch蛋白，并且LZTR-1与高尔基体复合体的结合是由其第二个BTB/POZ结构域介导的。
Members of the BTB-kelch superfamily play important roles during fundamental cellular processes, such as the regulation of cell morphology, migration, and gene expression. The BTB-kelch protein LZTR-1is deleted in the majority of DiGeorge syndrome patients and is believed to act as a transcriptional regulator. However, functional and expression profiling studies of LZTR-1 have not been performed thus far. Therefore, we examined the subcellular localization and function of LZTR-1 to gain insights into its biological role. Analysis of the primary structure of the protein revealed six N-terminal kelch motifs and two BTB/POZ domains at the C terminus within LZTR-1. Confocal analysis of the subcellular distribution of LZTR-1 using the Golgi markers GM130, Golgin-97, and TGN46 identified a localization of LZTR-1 exclusively on the cytoplasmic surface of the Golgi network that is mediated by its second BTB/POZ domain. In contrast to most other BTB-kelch proteins, LZTR-1 did not co-localize with actin. Treatment with brefeldin A did not lead to redistribution of LZTR-1 to the endoplasmic reticulum but caused its relocalization in dispersed, punctuated structures that were also positive for GM130. These data demonstrate that LZTR-1 is a Golgi matrix-associated protein. Upon induction of apoptosis, LZTR-1 was phosphorylated on tyrosine residues and subsequently degraded; that could be rescued partially by the addition of the caspase inhibitor Z-VAD-fmk and the proteasome inhibitors lactacystin and MG132. Taken together, our experiments identify LZTR-1 as the first BTB-kelch protein that exclusively localizes to the Golgi network, and the binding of LZTR-1 to the Golgi complex is mediated by its second BTB/POZ domain.