Double prenylation of SNARE protein Ykt6 is required for lysosomal hydrolase trafficking
Double prenylation of SNARE protein Ykt6 is required for lysosomal hydrolase trafficking
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溶酶体水解酶运输需要 SNARE 蛋白 Ykt6 的双异戊二烯化
DOI：
10.1093/jb/mvaa111
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Horiuchi Hisanori
中科院分区：
文献类型：
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作者：
Sakata Natsumi;Shirakawa Ryutaro;Goto Kota;Trinh Duc Anh;Horiuchi Hisanori
Ykt 6是一种进化上保守的SNARE蛋白，调节高尔基体膜融合和其他不同的膜运输途径。与大多数SNARE蛋白不同，Ykt 6缺乏跨膜结构域，而是在C末端具有串联半胱氨酸基序。最近，我们已经证明，Ykt 6经历双异戊二烯化在C-末端的两个半胱氨酸首先由法尼基转移酶，然后由一个新发现的蛋白异戊二烯转移酶命名为香叶基香叶基转移酶III型（GGT酶-III）。GGT酶-III由一个新的α亚基异戊烯基转移酶α亚基重复1（PTAR 1）和Rab香叶基香叶基转移酶β亚基组成。PTAR 1敲除（KO）细胞，其中Ykt 6是单一的异戊烯化与法呢基部分，表现出结构和功能异常的高尔基体与延迟的内高尔基体运输和受损的蛋白质糖基化。目前尚不清楚Ykt 6的第二个异戊烯化是否需要适当的运输溶酶体水解酶从高尔基体到溶酶体。在这里，我们发现，溶酶体水解酶，组织蛋白酶D和β-氨基己糖苷酶，在trans-Golgi网络中被错误分选，并分泌到PTAR 1 KO细胞的细胞外空间。此外，这些水解酶的成熟受到干扰。自噬标志物LC 3B在PTAR 1 KO细胞中积累，表明细胞降解途径存在缺陷。因此，双异戊烯化Ykt 6，而不是单异戊烯化Ykt 6，是关键的有效的排序和运输的酸性水解酶的溶酶体。
Ykt6 is an evolutionarily conserved SNARE protein regulating Golgi membrane fusion and other diverse membrane trafficking pathways. Unlike most SNARE proteins, Ykt6 lacks a transmembrane domain but instead has a tandem cysteine motif at the C-terminus. Recently, we have demonstrated that Ykt6 undergoes double prenylation at the C-terminal two cysteines first by farnesyltransferase and then by a newly identified protein prenyltransferase named geranylgeranyltransferase type-III (GGTase-III). GGTase-III consists of a novel α subunit prenyltransferase alpha subunit repeat containing 1 (PTAR1) and the β subunit of Rab geranylgeranyltransferase. PTAR1 knockout (KO) cells, where Ykt6 is singly prenylated with a farnesyl moiety, exhibit structural and functional abnormalities in the Golgi apparatus with delayed intra-Golgi trafficking and impaired protein glycosylation. It remains unclear whether the second prenylation of Ykt6 is required for proper trafficking of lysosomal hydrolases from Golgi to lysosomes. Here, we show that lysosomal hydrolases, cathepsin D and β-hexosaminidase, were missorted at thetrans-Golgi network and secreted into the extracellular space in PTAR1 KO cells. Moreover, maturation of these hydrolases was disturbed. LC3B, an autophagy marker, was accumulated in PTAR1 KO cells, suggesting defects in cellular degradation pathways. Thus, doubly prenylated Ykt6, but not singly prenylated Ykt6, is critical for the efficient sorting and trafficking of acid hydrolases to lysosomes.