Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
Int J Parasitol. 2010 Jul;40(8):929-35. doi: 10.1016/j.ijpara.2010.01.001. Epub 2010 Jan 22.
cAMP-dependent protein kinases (PKAs) are the main transducers of cAMP signalling in eukaryotic cells. Recently we reported the identification and characterisation of a PKA catalytic subunit (SmPKA-C) in Schistosoma mansoni that is required for adult schistosome viability in vitro. To gain further insights into the role of SmPKA-C in biological processes during the schistosome life cycle, we undertook a quantitative analysis of SmPKA-C mRNA expression in different life cycle stages. Our data shows that SmPKA-C mRNA expression is developmentally regulated, with the highest levels of expression in cercariae and adult female worms. To evaluate the biological role of SmPKA-C in these developmental stages, cercariae and adult worms were treated with various concentrations of PKA inhibitors. Treatment of cercariae with H-89 or PKI 14-22 amide resulted in loss of viability suggesting that, as in adults, PKA is an essential enzyme activity in this infectious larval stage. In adult worms, in vitro exposure to sub-lethal concentrations of H-89 or PKI 14-22 amide resulted in inhibition of egg production in a dose-dependent manner. Furthermore, using a murine model of schistosome infection where S. mansoni fecundity is impaired, we show that reduced rates of egg production in vivo correlate with significant reductions in SmPKA-C mRNA expression and PKA activity. Finally, restoration of parasite egg production in vivo also resulted in normalisation of SmPKA-C mRNA expression and PKA activity. Taken together, our data suggest that PKA signalling is required for cercarial viability and may play a specific role in the reproductive activity of adult worms.
环腺苷酸依赖的蛋白激酶（PKA）是真核细胞中环腺苷酸信号转导的主要介质。最近，我们报道了曼氏血吸虫中一种 PKA 催化亚基（SmPKA-C）的鉴定和特性，该亚基对于曼氏血吸虫在体外的成虫活力是必需的。为了更深入地了解 SmPKA-C 在血吸虫生命周期中的生物学过程中的作用，我们对不同生命周期阶段的 SmPKA-C mRNA 表达进行了定量分析。我们的数据表明，SmPKA-C mRNA 的表达受到发育调控，在尾蚴和雌性成虫中表达水平最高。为了评估 SmPKA-C 在这些发育阶段的生物学作用，我们用不同浓度的 PKA 抑制剂处理尾蚴和成虫。用 H-89 或 PKI 14-22 酰胺处理尾蚴会导致活力丧失，这表明，与成虫一样，PKA 是这个传染性幼虫阶段的必需酶活性。在成虫中，体外暴露于亚致死浓度的 H-89 或 PKI 14-22 酰胺会导致产卵抑制呈剂量依赖性。此外，我们使用曼氏血吸虫感染的小鼠模型，该模型中寄生虫的生殖力受损，我们发现体内产卵率的降低与 SmPKA-C mRNA 表达和 PKA 活性的显著降低相关。最后，体内寄生虫产卵率的恢复也导致 SmPKA-C mRNA 表达和 PKA 活性的正常化。总之，我们的数据表明 PKA 信号对于尾蚴活力是必需的，并且可能在成虫的生殖活性中发挥特定作用。
