Biggs Jason S, Olivera Baldomero M, Kantor Yuri I
University of Guam Marine Laboratory, UOG Station, Mangilao, GU 96923, USA.
Toxicon. 2008 Jul;52(1):101-5. doi: 10.1016/j.toxicon.2008.05.004. Epub 2008 May 29.
To date, studies conducted on cone snail venoms have attributed the origins of this complex mixture of neuroactive peptides entirely to gene expression by the secretory cells lining the lumen of the venom duct. However, specialized tissues such as the salivary glands also secrete their contents into the anterior gut and could potentially contribute some venom components injected into target animals; evidence supporting this possibility is reported here. Sequence analysis of a cDNA library created from a salivary gland of Conus pulicarius revealed the expression of two transcripts whose predicted gene products, after post-translational processing, strikingly resemble mature conopeptides belonging to the alpha-conotoxin family. These two transcripts, like alpha-conotoxin transcripts, putatively encode mature peptides containing the conserved A-superfamily cysteine pattern (CC-C-C) but the highly conserved A-superfamily signal sequences were not present. Analysis of A-superfamily members expressed in the venom duct of the same C. pulicarius specimens revealed three putative alpha-conotoxin sequences; the salivary gland transcripts were not found in the venom duct cDNA library, suggesting that these alpha-conotoxins are salivary gland specific. Therefore, expression of conotoxin-like gene products by the salivary gland could potentially add to the complexity of Conus venoms.
迄今为止，针对芋螺毒液开展的研究将这种复杂的神经活性肽混合物的来源完全归因于毒液管腔内衬分泌细胞的基因表达。然而，诸如唾液腺等特殊组织也会将其分泌物排入前肠，并且可能会为注入目标动物体内的一些毒液成分做出贡献；本文报告了支持这一可能性的证据。对从康氏芋螺唾液腺构建的cDNA文库进行的序列分析揭示了两种转录本的表达，其预测的基因产物在经过翻译后加工后，与属于α-芋螺毒素家族的成熟芋螺肽惊人地相似。这两种转录本与α-芋螺毒素转录本一样，推测编码含有保守的A超家族半胱氨酸模式（CC-C-C）的成熟肽，但不存在高度保守的A超家族信号序列。对同一康氏芋螺样本毒液管中表达的A超家族成员进行分析，发现了三个推测的α-芋螺毒素序列；在毒液管cDNA文库中未发现唾液腺转录本，这表明这些α-芋螺毒素是唾液腺特异性的。因此，唾液腺中类芋螺毒素基因产物的表达可能会增加芋螺毒液的复杂性。
