Department of Biological Sciences, The University of Southern Mississippi, 118 College Drive # 5018, Hattiesburg, MS 39406, USA.
Insect Biochem Mol Biol. 2013 Sep;43(9):781-93. doi: 10.1016/j.ibmb.2013.05.011. Epub 2013 Jun 13.
Glutaminyl cyclase (QC) catalyzes the cyclization of N-terminal glutamine residues into pyroglutamate. This post-translational modification extends the half-life of peptides and, in some cases, is essential in binding to their cognate receptor. Due to its potential role in the post-translational modification of tick neuropeptides, we report the molecular, biochemical and physiological characterization of salivary gland QC during the prolonged blood feeding of the black-legged tick (Ixodes scapularis) and the gulf-coast tick (Amblyomma maculatum). QC sequences from I. scapularis and A. maculatum showed a high degree of amino acid identity to each other and other arthropods and residues critical for zinc binding/catalysis (D159, E202, and H330) or intermediate stabilization (E201, W207, D248, D305, F325, and W329) are conserved. Analysis of QC transcriptional gene expression kinetics depicts an upregulation during the bloodmeal of adult female ticks prior to fast-feeding phases in both I. scapularis and A. maculatum suggesting a functional link with bloodmeal uptake. QC enzymatic activity was detected in saliva and extracts of tick salivary glands and midguts. Recombinant QC was shown to be catalytically active. Furthermore, knockdown of QC transcript by RNA interference resulted in lower enzymatic activity, and small, unviable egg masses in both studied tick species as well as lower engorged tick weights for I. scapularis. These results suggest that the post-translational modification of neurotransmitters and other bioactive peptides by QC is critical to oviposition and potentially other physiological processes. Moreover, these data suggest that tick-specific QC-modified neurotransmitters/hormones or other relevant parts of this system could potentially be used as novel physiological targets for tick control.
谷氨酰胺环化酶 (QC) 催化 N 端谷氨酰胺残基环化为焦谷氨酸。这种翻译后修饰延长了肽的半衰期，在某些情况下，对于与同源受体结合至关重要。由于其在蜱神经肽的翻译后修饰中的潜在作用，我们报告了在黑腿蜱 (Ixodes scapularis) 和海湾岸蜱 (Amblyomma maculatum) 的长时间血液喂养过程中唾液腺 QC 的分子、生化和生理特征。来自 I. scapularis 和 A. maculatum 的 QC 序列彼此之间以及与其他节肢动物具有高度的氨基酸同一性，并且对锌结合/催化至关重要的残基 (D159、E202 和 H330) 或中间稳定化至关重要的残基 (E201、W207、D248、D305、F325 和 W329) 保守。QC 转录基因表达动力学分析表明，在 I. scapularis 和 A. maculatum 成年雌性蜱的血液餐之前，快速喂养阶段之前，QC 基因表达上调，这表明与血液餐摄取有功能联系。在唾液和蜱唾液腺和中肠提取物中检测到 QC 酶活性。显示重组 QC 具有催化活性。此外，通过 RNA 干扰敲低 QC 转录本导致两种研究的蜱种的酶活性降低，并且产卵量小且不可育，以及 I. scapularis 的饱血蜱体重降低。这些结果表明，QC 对神经递质和其他生物活性肽的翻译后修饰对于产卵和潜在的其他生理过程至关重要。此外，这些数据表明，蜱特异性 QC 修饰的神经递质/激素或该系统的其他相关部分可能可作为蜱控制的新型生理靶标。
