Characterization of Drosophila aspartic proteases that induce the secretion of a Golgi-resident transferase, heparan sulfate 6-O-sulfotransferase
Characterization of Drosophila aspartic proteases that induce the secretion of a Golgi-resident transferase, heparan sulfate 6-O-sulfotransferase
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DOI：
10.1093/jb/mvi034
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发表时间：
2005-03-01
影响因子：
2.7
通讯作者：
Hashimoto, Y
中科院分区：
文献类型：
--
作者：
Kotani, N;Kitazume, S;Hashimoto, Y
阿尔茨海默氏β-分泌酶(BACE1)是一种天冬氨酸蛋白酶，它分解淀粉样前体蛋白产生一种神经毒肽-淀粉样蛋白-P，它在引发阿尔茨海默氏病中发挥作用。我们先前发现BACE1还裂解糖基转移酶--α-2，6-唾液酸基转移酶，作为一种生理底物。在本研究中，我们进行了生物同源性搜索，鉴定了两个与人BACE1同源的果蝇天冬氨酸蛋白酶，并分离了它们的cDNA。这些基因编码的蛋白质分别命名为DASP1和DASP2，分别与人BACE1有59%和50%的相似性。每个蛋白质都含有一对活性中心基序(Asp/Thr或Ser/Gly)，这是包括BACE1在内的天冬氨酸蛋白酶的共同特征。虽然DASP1和DASP2没有明显的跨膜结构域，但在COS细胞中过度表达的蛋白酶定位于高尔基体区域。S2细胞中高表达的DASP1有部分分泌，而DASP2无分泌。DASP1转录本在果蝇头部表达，而DASP2转录本主要在果蝇体内表达。当DASP1或DASP2与高尔基体驻留转移酶--果蝇硫酸乙酰肝素6-O-磺酸转移酶共表达时，该酶能促进细胞分泌该转移酶，表明DASP1和DASP2都能诱导6-O-磺酸转移酶的分泌。
Alzheimer's beta-secretase (BACE1), an aspartic protease, cleaves amyloid precursor protein to produce a neurotoxic peptide, amyloid-P, which plays a role in triggering Alzheimer's disease. We previously found that BACE1 also cleaves a glycosyltransferase, alpha 2,6-sialyltransferase, as a physiological substrate. In the present study, we performed a BIAST homology search, identified two Drosophila aspartic proteases that are homologous to human BACE1, and isolated their cDNAs. The proteins encoded by the cDNAs were designated as DASP1 and DASP2, which exhibited 59% and 50% similarity to human BACE1, respectively. Each protein contained a pair of active site motifs (Asp/Thr or Ser/Gly), which is a common characteristic of aspartic proteases including BACE1. Although DASP1 and DASP2 did not contain an apparent transmenbrane domain, the proteases overexpressed in COS cells were localized in the Golgi area. Some of the DASP1 overexpressed in S2 cells was secreted, but none of the DASP2 was. DASP1 transcripts were expressed in the head of fruitflies, whereas DASP2 transcripts were mainly expressed in the body. When either DASP1 or DASP2 was coexpressed together with a Golgi-resident transferase, Drosophila heparan sulfate 6-O-sulfotransferase, the protease enhanced the secretion of the transferase from the cells, indicating that both DASP1 and DASP2 can induce the secretion of the 6-O-sulfotransferase.