Elements of the C-terminal t peptide of acetylcholinesterase that determine amphiphilicity, homomeric and heteromeric associations, secretion and degradation
Elements of the C-terminal t peptide of acetylcholinesterase that determine amphiphilicity, homomeric and heteromeric associations, secretion and degradation
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DOI：
10.1111/j.1432-1033.2004.04052.x
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发表时间：
2004-04-01
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影响因子：
--
通讯作者：
Bon, S
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文献类型：
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作者：
Belbeoc'h, S;Falasca, C;Bon, S
脊椎动物乙酰胆碱酯酶(AChE)T亚基的C-末端t肽(40个残基)含有一系列7个保守的芳香族残基，形成一个两亲性的α-螺旋；它允许形成同源低聚物(单体、二聚体和四聚体)，并允许与锚定蛋白ColQ和Prima形成异构体结合，这些锚定蛋白包含一个富含脯氨酸的基序(PRAD)。我们分析了Torpedo AChE(T)的T肽突变对寡聚和分泌的影响。荷电残基对同源低聚物的分布有影响，但对与COLQ N端片段Q(N)的异构体结合作用影响不大。同型四聚体和Q(N)连接的四聚体的形成需要一个由四个芳香族残基组成的中心核心和一个延伸到31个残基的肽段；最后九个残基(32-40)不是必需的，尽管半胱氨酸C37形成的二硫键稳定了T-4和T-4-Q(N)四聚体。T肽(EL)的最后两个残基引起部分细胞内滞留；用KDEL取代C端的CAEL四肽并不能阻止四聚化和与Q(N)的异构体结合，表明这些结合发生在内质网中。研究发现，破坏t肽的α-螺旋结构的突变会促进降解。与Q(N)共表达通常会增加分泌量，主要是以T-4-Q(N)复合体的形式存在，但也有一些突变体会减少分泌量。因此，这个小的、自主的相互作用结构域中的突变带来了关于决定AChE(T)亚单位的寡聚关联以及在分泌和降解之间选择的特征的信息。
The C-terminal t peptide (40 residues) of vertebrate acetylcholinesterase (AChE) T subunits possesses a series of seven conserved aromatic residues and forms an amphiphilic alpha-helix; it allows the formation of homo-oligomers (monomers, dimers and tetramers) and heteromeric associations with the anchoring proteins, ColQ and PRiMA, which contain a proline-rich motif (PRAD). We analyzed the influence of mutations in the t peptide of Torpedo AChE(T) on oligomerization and secretion. Charged residues influenced the distribution of homo-oligomers but had little effect on the heteromeric association with Q(N), a PRAD-containing N-terminal fragment of ColQ. The formation of homo-tetramers and Q(N)-linked tetramers required a central core of four aromatic residues and a peptide segment extending to residue 31; the last nine residues (32-40) were not necessary, although the formation of disulfide bonds by cysteine C37 stabilized T-4 and T-4-Q(N) tetramers. The last two residues of the t peptide (EL) induced a partial intracellular retention; replacement of the C-terminal CAEL tetrapeptide by KDEL did not prevent tetramerization and heteromeric association with Q(N), indicating that these associations take place in the endoplasmic reticulum. Mutations that disorganize the alpha-helical structure of the t peptide were found to enhance degradation. Co-expression with Q(N) generally increased secretion, mostly as T-4-Q(N) complexes, but reduced it for some mutants. Thus, mutations in this small, autonomous interaction domain bring information on the features that determine oligomeric associations of AChE(T) subunits and the choice between secretion and degradation.