EDEM3, a soluble EDEM homolog, enhances glycoprotein endoplasmic reticulum-associated degradation and mannose trimming
EDEM3, a soluble EDEM homolog, enhances glycoprotein endoplasmic reticulum-associated degradation and mannose trimming
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DOI：
10.1074/jbc.m512191200
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发表时间：
2006-04-07
影响因子：
4.8
通讯作者：
Hosokawa, N
中科院分区：
文献类型：
--
作者：
Hirao, K;Natsuka, Y;Hosokawa, N
内质网中的质量控制确保只有正确折叠的蛋白质通过在称为内质网相关降解（ERAD）的过程中识别和丢弃错误折叠或未组装蛋白质的机制保留在细胞中。我们先前克隆了EDEM（ER降解增强α-甘露糖苷酶样蛋白），并表明它加速错误折叠糖蛋白的ERAD。我们现在克隆了小鼠EDEM 3，EDEM的可溶性同源物。EDEM 3由931个氨基酸组成，并且在其N-末端结构域中具有I类α-甘露糖苷酶（糖基水解酶家族47）的所有特征基序，并且在其C-末端区域中具有蛋白酶相关基序。EDEM 3在转染的HEK 293细胞中加速糖蛋白ERAD，如通过错误折叠的α 1-抗胰蛋白酶变体（null（Hong Kong））和TCR α的降解增加所示。EDEM 3的过表达还极大地刺激甘露糖修剪，不仅从错误折叠的α 1-AT空（香港），而且从总糖蛋白，与EDEM相反，其没有明显的α 1，2-甘露糖苷酶活性。此外，E147 Q EDEM 3突变体（其在α 1，2-甘露糖苷酶的酶活性所必需的保守酸性残基之一中具有突变）的过表达消除了甘露糖修剪的刺激，并大大降低了EDEM 3对ERAD的刺激。这些结果表明，EDEM 3在体内具有α 1，2-甘露糖苷酶活性，表明EDEM 3促进糖蛋白ERAD的机制与EDEM不同。
Quality control in the endoplasmic reticulum ensures that only properly folded proteins are retained in the cell through mechanisms that recognize and discard misfolded or unassembled proteins in a process called endoplasmic reticulum-associated degradation (ERAD). We previously cloned EDEM ( ER degradation-enhancing alpha-mannosidase- like protein) and showed that it accelerates ERAD of misfolded glycoproteins. We now cloned mouse EDEM3, a soluble homolog of EDEM. EDEM3 consists of 931 amino acids and has all the signature motifs of Class I alpha-mannosidases ( glycosyl hydrolase family 47) in its N-terminal domain and a protease-associated motif in its C-terminal region. EDEM3 accelerates glycoprotein ERAD in transfected HEK293 cells, as shown by increased degradation of misfolded alpha 1-antitrypsin variant ( null ( Hong Kong)) and of TCR alpha. Overexpression of EDEM3 also greatly stimulates mannose trimming not only from misfolded alpha 1-AT null ( Hong Kong) but also from total glycoproteins, in contrast to EDEM, which has no apparent alpha 1,2-mannosidase activity. Furthermore, overexpression of the E147Q EDEM3 mutant, which has the mutation in one of the conserved acidic residues essential for enzyme activity of alpha 1,2-mannosidases, abolishes the stimulation of mannose trimming and greatly decreases the stimulation of ERAD by EDEM3. These results show that EDEM3 has alpha 1,2-mannosidase activity in vivo, suggesting that the mechanism whereby EDEM3 accelerates glycoprotein ERAD is different from that of EDEM.