Center for Vector-Borne Disease, University of Rhode Island, Kingston, RI 02881, USA.
BMC Biochem. 2011 Jun 27;12:32. doi: 10.1186/1471-2091-12-32.
Ixodes scapularis, commonly known as the blacklegged or deer tick, is the main vector of Lyme disease in the United States. Recent progress in transcriptome research has uncovered hundreds of different proteins expressed in the salivary glands of hard ticks, the majority of which have no known function, and include many novel protein families. We recently identified transcripts coding for two putative cytosolic sulfotransferases in these ticks which recognized phenolic monoamines as their substrates. In this current study, we characterize the genetic expression of these two cytosolic sulfotransferases throughout the tick life cycle as well as the enzymatic properties of the corresponding recombinant proteins. Interestingly, the resultant recombinant proteins showed sulfotransferase activity against both neurotransmitters dopamine and octopamine.
The two sulfotransferase genes were coded as Ixosc SULT 1 & 2 and corresponding proteins were referred as Ixosc Sult 1 and 2. Using gene-specific primers, the sulfotransferase transcripts were detected throughout the blacklegged tick life cycle, including eggs, larvae, nymphs, adult salivary glands and adult midgut. Notably, the mRNA and protein levels were altered upon feeding during both the larval and nymphal life stages. Quantitative PCR results confirm that Ixosc SULT1 was statistically increased upon blood feeding while Ixosc SULT 2 was decreased. This altered expression led us to further characterize the function of these proteins in the Ixodid tick. The sulfotransferase genes were cloned and expressed in a bacterial expression system, and purified recombinant proteins Ixosc Sult 1(R) and 2(R) showed sulfotransferase activity against neurotransmitters dopamine and octopamine as well as the common sulfotransferase substrate p-nitrophenol. Thus, dopamine- or octopamine-sulfonation may be involved in altering the biological signal for salivary secretion in I. scapularis.
Collectively, these results suggest that a function of Ixosc Sult 1 and Sult 2 in Ixodid tick salivary glands may include inactivation of the salivation signal via sulfonation of dopamine or octopamine.
Ixodes scapularis，通常被称为黑腿或鹿蜱，是美国莱姆病的主要传播媒介。转录组研究的最新进展揭示了硬蜱唾液腺中表达的数百种不同蛋白质，其中大多数蛋白质的功能未知，包括许多新的蛋白质家族。我们最近在这些蜱中鉴定出编码两种推定的细胞质磺基转移酶的转录本，这些酶将酚单胺识别为其底物。在本研究中，我们描述了这两种细胞质磺基转移酶在整个蜱生命周期中的基因表达情况，以及相应重组蛋白的酶学特性。有趣的是，所得重组蛋白对神经递质多巴胺和章鱼胺均表现出磺基转移酶活性。
这两个磺基转移酶基因被编码为 Ixosc SULT 1 和 2，相应的蛋白质被称为 Ixosc Sult 1 和 2。使用基因特异性引物，在黑腿蜱的整个生命周期中都检测到了磺基转移酶转录本，包括卵、幼虫、若虫、成蜱唾液腺和成蜱中肠。值得注意的是，在幼虫和若虫阶段的取食过程中，mRNA 和蛋白质水平都发生了改变。定量 PCR 结果证实，Ixosc SULT1 在血液取食时统计学上增加，而 Ixosc SULT 2 则减少。这种表达的改变促使我们进一步研究这些蛋白质在蜱中的功能。磺基转移酶基因在细菌表达系统中克隆和表达，并纯化了重组蛋白 Ixosc Sult 1(R)和 2(R)，它们对神经递质多巴胺和章鱼胺以及常见的磺基转移酶底物对硝基苯酚具有磺基转移酶活性。因此，多巴胺或章鱼胺的磺化可能参与了改变 I. scapularis 唾液分泌的生物学信号。
总之，这些结果表明，Ixosc Sult 1 和 Sult 2 在蜱唾液腺中的功能可能包括通过多巴胺或章鱼胺的磺化使唾液分泌信号失活。
