Second messenger signaling controls a surprisingly diverse range of processes in several eukaryotic pathogens. Molecular machinery and pathways involving these messengers thus hold tremendous opportunities for therapeutic interventions. Relative to Ca²⁺ signaling, the knowledge of a crucial second messenger cyclic AMP (cAMP) and its signaling pathway is very scant in the intestinal parasite Entamoeba histolytica. In the current study, mining the available genomic resources, we have for the first time identified the cAMP signal transduction pathway of E. histolytica. Three heptahelical proteins with variable G-protein-coupled receptor domains, heterotrimeric G-proteins (Gα, Gβ, and Gγ subunits), soluble adenylyl cyclase, cyclase-associated protein, and enzyme carbonic anhydrase were identified in its genome. We could also identify several putative candidate genes for cAMP downstream effectors such as protein kinase A, A-kinase anchoring proteins, and exchange protein directly activated by the cAMP pathway. Using specific inhibitors against key identified targets, we could observe changes in the intracellular cAMP levels as well as defect in the rate of phagocytosis of red blood cells by the parasite E. histolytica. We thus strongly believe that characterization of some of these unexplored crucial signaling determinants will provide a paradigm shift in understanding the pathogenicity of this organism.

第二信使信号控制了几种真核病原体中令人惊讶的多样化过程。因此，涉及这些信使的分子机制和途径为治疗干预提供了巨大的机会。相对于Ca ²⁺信号，关键的第二信使环AMP（cAMP）及其信号传导途径的知识在肠道寄生虫中非常少溶组织性变形虫。在当前的研究中，通过挖掘可用的基因组资源，我们首次确定了cAMP信号转导途径溶组织性大肠杆菌。在其基因组中鉴定出三种具有可变G蛋白偶联受体结构域的七螺旋蛋白，异三聚体G蛋白（Gα，Gβ和Gγ亚基），可溶性腺苷酸环化酶，环化酶相关蛋白和碳酸酐酶。我们还可以为cAMP下游效应子确定几个推定的候选基因，例如蛋白激酶A，A激酶锚定蛋白和被cAMP途径直接激活的交换蛋白。使用针对关键已鉴定靶标的特异性抑制剂，我们可以观察到细胞内cAMP水平的变化以及寄生虫对红细胞吞噬作用速率的缺陷溶组织性大肠杆菌。因此，我们坚信，某些未探索的关键信号决定因素的表征将为理解该生物的致病性提供范式转变。