LAPTM4α is targeted from the Golgi to late endosomes/lysosomes in a manner dependent on the E3 ubiquitin ligase Nedd4-1 and ESCRT proteins
LAPTM4α is targeted from the Golgi to late endosomes/lysosomes in a manner dependent on the E3 ubiquitin ligase Nedd4-1 and ESCRT proteins
复制标题
LAPTM4α 以依赖于 E3 泛素连接酶 Nedd4-1 和 ESCRT 蛋白的方式从高尔基体靶向晚期内体/溶酶体
DOI：
10.1016/j.bbrc.2021.03.151
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发表时间：
2021
影响因子：
3.1
通讯作者：
Fujimoto Keiko
中科院分区：
文献类型：
--
作者：
Hirota Yuko;Hayashi Masaharu;Miyauchi Yuu;Ishii Yuji;Tanaka Yoshitaka;Fujimoto Keiko
溶酶体相关蛋白跨膜4α（Lysosome-associated protein transmembrane 4α，LAPTM 4 α）是一种主要定位于内体和溶酶体的跨膜蛋白，在其C端胞质结构域具有几个推定的溶酶体靶向信号，包括酪氨酸基序（YxxΦ）和PY基序（L/PxxY）。LAPTM 4 α以前已被证明是由E3泛素连接酶Nedd 4 -1通过结合到其PY基序和分选到溶酶体的泛素化，然而，LAPTM 4 α定位到内体/溶酶体的分子机制尚未完全阐明。在本研究中，我们发现LAPTM 4 α以依赖于PY基序的方式结合Nedd 4 -1，而PY基序和Nedd 4 -1不一定是LAPTM 4 α泛素化所必需的。然而，LAPTM 4 α与Nedd 4 -1的结合对于LAPTM 4 α从高尔基体到晚期内体/溶酶体的有效分选是必需的。一个意想不到的发现是LAPTM 4 α定位于晚期内体的管腔中，但不在界膜中，并随时间在溶酶体中降解。有趣的是，我们进一步发现，siRNA敲低转运所需的内体分选复合物（ESCRT）组分（介导泛素化膜蛋白分选进入内体的腔内囊泡（ILV））选择性阻断LAPTM 4 α转运至内体。总的来说，这些结果表明，LAPTM 4 α从高尔基体到内体的运输是通过与Nedd 4 -1的相互作用促进的，这进一步需要ESCRT组分。此外，我们的研究结果突出了一个新的功能ESCRT蛋白介导的蛋白质和/或囊泡运输从高尔基体的内体/溶酶体。
Lysosome-associated protein transmembrane 4α (LAPTM4α) is a four transmembrane-spanning protein primarily localized in endosomes and lysosomes and has several putative lysosomal targeting signals at its C-terminal cytoplasmic domain, including tyrosine-based motifs (YxxΦ) and PY motifs (L/PxxY). LAPTM4α has been previously shown to be ubiquitinated by the E3 ubiquitin ligase Nedd4-1 through binding to its PY motifs and sorted to lysosomes, however, the molecular mechanisms underlying the localization of LAPTM4α to endosomes/lysosomes have not yet been fully elucidated. In the present study, we show that LAPTM4α binds Nedd4-1 in a manner dependent on PY motifs, while the PY motifs and Nedd4-1 are not necessarily required for LAPTM4α ubiquitination. The binding of LAPTM4α with Nedd4-1, however, is necessary for an effective sorting of LAPTM4α from the Golgi to late endosomes/lysosomes. An unexpected finding is that LAPTM4α is localized in the lumen, but not in the limiting membrane, of late endosomes, and degraded in lysosomes over time. Interestingly, we further found that siRNA knockdown of endosomal sorting complexes required for transport (ESCRT) components that mediate sorting of ubiquitinated membrane proteins into intralumenal vesicles (ILVs) of endosomes selectively blocks the transport of LAPTM4α to endosomes. Collectively, these results suggest that trafficking of LAPTM4α from the Golgi to endosomes is promoted by the interaction with Nedd4-1, which further requires ESCRT components. Furthermore, our findings highlight a novel function for ESCRT proteins in mediating protein and/or vesicle trafficking from the Golgi to endosomes/lysosomes.