Conserved domain structure of beta-neurexins. Unusual cleaved signal sequences in receptor-like neuronal cell-surface proteins.
Conserved domain structure of beta-neurexins. Unusual cleaved signal sequences in receptor-like neuronal cell-surface proteins.
复制标题
β-神经毒素的保守结构域结构。
DOI：
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发表时间：
1994
影响因子：
4.8
通讯作者：
T. Südhof
中科院分区：
文献类型：
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作者：
Y. Ushkaryov;Y. Hata;K. Ichtchenko;C. Moomaw;S. Afendis;C. Slaughter;T. Südhof
神经毒素是神经元细胞表面蛋白家族，由较长的 α-神经毒素（I α、II α 和 III α）和较短的 β-神经毒素（I β 和 II β）组成，具有相同的 C 末端但不同的 N 末端。 α-神经毒素具有细胞表面受体的结构，但β-神经毒素的膜拓扑结构和保守性尚不清楚。我们现在已经鉴定了编码牛神经毒素Iβ和IIIβ的cDNA克隆，从而证明了神经毒素III的β形式的存在以及哺乳动物中β-神经毒素的进化保守性。与α-neurexins类似，β-neurexins在COS细胞中转染表达后被发现高度O-糖基化，这表明α-和β-neurexins利用相同的O-糖基化盒并具有相似的跨膜方向。为了确定 β-neurexin 是否含有用于膜易位的切割或未切割的信号序列，在 COS 细胞中表达 β-neurexin-IgG 融合蛋白，并直接对它们的 N 末端进行测序。这表明所有三个 β-neurexins 的 N 末端都包含不寻常的切割信号序列。我们的数据共同表明，所有已知的神经毒素基因都会产生具有相似跨膜组织和受体样结构的α和β形式。由于存在长的非典型切割信号肽，β-神经毒素在剪接到 α-神经毒素序列之前仅包含一个短的独特序列。因此，β-神经毒素本质上是N末端截短的α-神经毒素。
Neurexins, a family of neuronal cell-surface proteins, consist of the longer alpha-neurexins (I alpha, II alpha, and III alpha) and the shorter beta-neurexins (I beta and II beta) with identical C termini but distinct N termini. alpha-Neurexins have the structure of cell surface receptors, but the membrane topology and conservation of beta-neurexins is unknown. We have now characterized cDNA clones encoding bovine neurexins I beta and III beta, thereby demonstrating the presence of a beta-form for neurexin III and the evolutionary conservation of beta-neurexins in mammals. Similar to alpha-neurexins, beta-neurexins were found to be highly O-glycosylated after expression by transfection in COS cells, suggesting that alpha- and beta-neurexins utilize the same O-glycosylation cassette and have similar transmembrane orientations. To determine if beta-neurexins contain a cleaved or uncleaved signal sequence for membrane translocation, beta-neurexin-IgG fusion proteins were expressed in COS cells, and their N termini were directly sequenced. This revealed that the N terminus of all three beta-neurexins contains an unusual cleaved signal sequence. Together our data show that all known neurexin genes generate alpha and beta forms with similar transmembrane organizations and receptor-like structures. Due to the presence of a long atypical cleaved signal peptide, beta-neurexins contain only a short unique sequence before splicing into the alpha-neurexin sequence. Thus, beta-neurexins are essentially N terminally truncated alpha-neurexins.