Nucleotidyl Cyclase Activity of Particulate Guanylyl Cyclase A: Comparison with Particulate Guanylyl Cyclases E and F, Soluble Guanylyl Cyclase and Bacterial Adenylyl Cyclases Cyaa and Edema Factor

Abstract

Guanylyl cyclases (GCs) regulate many physiological processes by catalyzing the synthesis of the second messenger cGMP. The GC family consists of seven particulate GCs (pGCs) and a nitric oxide-activated soluble GC (sGC). Rat sGC α1β1 possesses much broader substrate specificity than previously assumed. Moreover, the exotoxins CyaA from Bordetella pertussis and edema factor (EF) from Bacillus anthracis possess nucleotidyl cyclase (NC) activity. pGC-A is a natriuretic peptide-activated homodimer with two catalytic sites that act cooperatively. Here, we studied the NC activity of rat pGC-A in membranes of stably transfected HEK293 cells using a highly sensitive and specific HPLC-MS/MS technique. GTP and ITP were effective, and ATP and XTP were only poor, pGC-A substrates. In contrast to sGC, pGC-A did not use CTP and UTP as substrates. pGC-E and pGC-F expressed in bovine rod outer segment membranes used only GTP as substrate. In intact HEK293 cells, pGC-A generated only cGMP. In contrast to pGCs, EF and CyaA showed very broad substrate-specificity. In conclusion, NCs exhibit different substrate-specificities, arguing against substrate-leakiness of enzymes and pointing to distinct physiological functions of cyclic purine and pyrimidine nucleotides.

Efficacy of Single and Combined Antibiotic Treatments of Anthrax in Rabbits

“…Effective postexposure therapy protocols preventing the establishment of fatal anthrax disease have been reported in the literature. Postexposure treatment with penicillin (10)(11)(12), doxycycline (10), ciprofloxacin (10,13), and levofloxacin (13) efficiently protected rhesus monkeys following inhalation of lethal doses of virulent B. anthracis spores. In guinea pigs, treatment with penicillin (14), doxycycline (15), tetracycline (16), ciprofloxacin (15,16), and erythromycin (16) protected the animals, but upon treatment termination, the animals died due to anthrax relapse (12,15,16).…”

PDE7A1 hydrolyzes cCMP

“…The cCMP degrading activity of PDE7A may even become more important during bacterial infections, since bacterial toxins like edema factor (EF) [25,26] or adenylyl cyclase toxin CyaA [26], both from Bacillus anthracis, produce cCMP. In addition, the P. aeruginosa type III secretion protein ExoY, which shows highly toxic effects in the rat model [27], produces a significant amount of cCMP in B103 and human lung carcinoma cell line (A549) cells [7].…”

Recent progress in the field of cIMP research

“…cIMP-induced vasoconstriction may play a role in coronary ischemia/reperfusion injury and/or cardiovascular complications in sleep apnea (Detremmerie et al, 2016). The occurrence of cIMP in only certain pathophysiological settings could be an explanation for the failure to detect cIMP in several biological systems under normal conditions, i.e., without hypoxia (Beste et al, 2013;Hartwig et al, 2014;Bähre et al, 2015). Detremmerie et al (2016) provide evidence in favor of the notion that the pharmacological actions of thymoquinone depend on sGC-catalyzed cIMP formation.…”

“…pGCs generate cIMP as well (Beste et al, 2013). Moreover, the "adenylyl cyclase" toxins CyaA from Bordetella pertussis and edema factor from Bacillus anthracis can generate cIMP (Beste et al, 2013).…”

“…Studies on various mammalian cell lines and mouse organs failed to detect cIMP (Beste et al, 2013;Hartwig et al, 2014;Bähre et al, 2015), raising doubts about a (patho)physiological role of cIMP (Seifert, 2014). However, the group of Vanhoutte showed that under conditions of hypoxia, sGC switches substrate specificity from GTP to ITP and that the generated cIMP exerts opposite (constrictory) effects on blood vessels to those of cGMP (dilatatory) (Chen et al, 2014;Gao and Vanhoutte, 2014).…”