Endogenous cAMP elevation in Brassica napus causes changes in phytohormone levels

In higher plants, the regulatory roles of cAMP (cyclic adenosine 3',5'-monophosphate) signaling remain elusive until now. Cellular cAMP levels are generally much lower in higher plants than in animals and transiently elevated for triggering downstream signaling events. Moreover, plant adenylate cyclase (AC) activities are found in different moonlighting multifunctional proteins, which may pose additional complications in distinguishing a specific signaling role for cAMP. Here, we have developed rapeseed (Brassica napus L.) transgenic plants that overexpress an inducible plant-origin AC activity for generating high AC levels much like that in animal cells, which served the genetic model disturbing native cAMP signaling as a whole in plants. We found that overexpression of the soluble AC activity had significant impacts on the contents of indole-3-acetic acid (IAA) and stress phytohormones, i.e. jasmonic acid (JA), abscisic acid (ABA), and salicylic acid (SA) in the transgenic plants. Acute induction of the AC activity caused IAA overaccumulation, and upregulation of TAA1 and CYP83B1 in the IAA biosynthesis pathways, but also simultaneously the hyper-induction of PR4 and KIN2 expression indicating activation of JA and ABA signaling pathways. We observed typical overgrowth phenotypes related to IAA excess in the transgenic plants, including significant increases in plant height, internode length, width of leaf blade, petiole length, root length, and fresh shoot biomass, as well as the precocious seed development, as compared to wild-type plants. In addition, we identified a set of 1465 cAMP-responsive genes (CRGs), which are most significantly enriched in plant hormone signal transduction pathway, and function mainly in relevance to hormonal, abiotic and biotic stress responses, as well as growth and development. Collectively, our results support that cAMP elevation impacts phytohormone homeostasis and signaling, and modulates plant growth and development. We proposed that cAMP signaling may be critical in configuring the coordinated regulation of growth and development in higher plants.

Comparison of the function of two novel human dopamine D2 receptor variants identifies a likely mechanism for their pathogenicity

Two recently discovered DRD2 mutations, c.634A > T, p.Ile212Phe and c.1121T > G, p.Met374Arg, cause hyperkinetic movement disorders that have overlapping features but apparently differ in severity. The two known carriers of the Met374Arg variant had early childhood disease onset and more severe motor, cognitive, and neuropsychiatric deficits than any known carriers of the Ile212Phe variant, whose symptoms were first apparent in adolescence. Here, we evaluated if differences in the function of the two variants in cultured cells could explain differing pathogenicity. Both variants were expressed less abundantly than the wild type receptor and exhibited loss of agonist-induced arrestin binding, but differences in expression and arrestin binding between the variants were minor. Basal and agonist-induced activation of heterotrimeric Gi/o/z proteins, however, showed clear differences; agonists were generally more potent at Met374Arg than at the Ile212Phe or wild type variants. Furthermore, all Gα subtypes tested were constitutively activated more by Met374Arg than by Ile212Phe. Met374Arg produced greater constitutive inhibition of cyclic AMP accumulation than Ile212Phe or the wild type D2 receptor. Met374Arg and Ile212Phe were more sensitive to thermal inactivation than the wild type D2 receptor, as reported for other constitutively active receptors, but Ile212Phe was affected more than Met374Arg. Additional pharmacological characterization suggested that the mutations differentially affect the shape of the agonist binding pocket and the potency of dopamine, norepinephrine, and tyramine. Molecular dynamics simulations provided a structural rationale for enhanced constitutive activation and agonist potency. Enhanced constitutive and agonist-induced G protein-mediated signaling likely contributes to the pathogenicity of these novel variants.

Adenylate cyclase activates the cAMP signalling pathway to enhance platelet-rich plasma-treated Achilles tendon disease, a theoretical bioinformatics-based study

The effectiveness of platelet-rich plasma (PRP) for the treatment of Achilles tendon disorders still needs to be evaluated through a series of prospective studies, but genomic analysis can reveal the existence of complementary PRP treatment options. Based on the 96 platelet activation-related genes in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, we performed Gene Ontology functional enrichment analysis and KEGG enrichment analysis, pathway correlation analysis, and enrichment mapping to determine the enrichment results of the gene set enrichment analysis and found that the cAMP signalling pathway may be the key to enhancing the effectiveness of PRP treatment. The cAMP signalling pathway interacts with the Rap1 signalling pathway and cGMP-PKG signalling pathway to mediate the entire pathophysiological process of Achilles tendon disease. Moreover, ADCY1-9 may be the key to the activation of the cAMP signalling network. Further based on the data in the Gene Expression Omnibus database, it was found that ADCY4 and ADCY7 may be the players that play a major role, associated with the STAT4-ADCY4-LAMA5 axis and the GRbeta-ADCY7-SEMA3C axis, which is expected to be a complementary target for enhancing the efficacy of PRP in the treatment of Achilles tendon disease.

Peptide-Mediated Cyclic Nucleotide Signaling in Plants: Identification and Characterization of Interactor Proteins with Nucleotide Cyclase Activity

During the last decades, an increasing number of plant signaling peptides have been discovered and it appears that many of them are specific ligands for interacting receptor molecules. These receptors can enable the formation of second messengers which in turn transmit the ligand-induced stimuli into complex and tunable downstream responses. In order to perform such complex tasks, receptor proteins often contain several distinct domains such as a kinase and/or adenylate cyclase (AC) or guanylate cyclase (GC) domains. ACs catalyze the conversion of ATP to 3',5'-cyclic adenosine monophosphate (cAMP) while GCs catalyze the reaction of GTP to 3',5'-cyclic guanosine monophosphate (cGMP). Both cAMP and cGMP are now recognized as essential components of many plant responses, including responses to peptidic hormones. Here we describe the approach that led to the discovery of the Plant Natriuretic Peptide Receptor (PNP receptor), including a protocol for the identification of currently undiscovered peptidic interactions, and the subsequent application of computational methods for the identification of AC and/or GC domains in such interacting receptor candidates.

Discovery of a potent and selective human AC2 inhibitor based on 7-deazapurine analogues of adefovir

Adefovir based acyclic nucleoside phosphonates were previously shown to modulate bacterial and, to a certain extent, human adenylate cyclases (mACs). In this work, a series of 24 novel 7-substituted 7-deazaadefovir analogues were synthesized in the form of prodrugs. Twelve analogues were single-digit micromolar inhibitors of Bordetella pertussis adenylate cyclase toxin with no cytotoxicity to J774A.1 macrophages. In HEK293 cell-based assays, compound 14 was identified as a potent (IC50 = 4.45 μM), non-toxic, and selective mAC2 inhibitor (vs. mAC1 and mAC5). Such a compound represents a valuable addition to a limited number of small-molecule probes to study the biological functions of individual endogenous mAC isoforms.

Role of the adenylate cyclase/cyclic AMP pathway in oxytocin-induced lacrimal gland myoepithelial cells contraction

The aim of these studies was to investigate the involvement of the second messenger 3',5'-cyclic adenosine monophosphate (cAMP) and its downstream effectors in oxytocin (OXT)-mediated lacrimal gland myoepithelial cell (MEC) contraction. Lacrimal gland MEC were isolated and propagated from alpha-smooth muscle actin (SMA)-GFP mice. RNA and protein samples were prepared to analyze G protein expression by RT-PCR and western blotting; respectively. Changes in intracellular cAMP concentration were measured using a competitive ELISA kit. To increase intracellular cAMP concentration, the following agents were used: forskolin (FKN, a direct activator of adenylate cyclase), 3-isobutyl-1-methylxanthine (IBMX, an inhibitor of the phosphodiesterase that hydrolyzes cAMP), or a cell permeant cAMP analog, dibutyryl (db)-cAMP. In addition, inhibitors and selective agonists were used to investigate the role of cAMP effector molecules, protein kinase A (PKA) and exchange protein activated by cAMP (EPAC) in OXT-induced MEC contraction. MEC contraction was monitored in real time and changes in cell size were quantified using ImageJ software. The adenylate cyclase coupling G proteins, Gαs, Gαo, and Gαi, are expressed in lacrimal gland MEC at both the mRNA and protein levels. OXT increased intracellular cAMP in a concentration-dependent manner. FKN, IBMX and db-cAMP significantly stimulated MEC contraction. Preincubation of cells with either Myr-PKI, a specific PKA inhibitor or ESI09, an EPAC inhibitor, resulted in almost complete inhibition of both FKN- as well as OXT-stimulated MEC contraction. Finally, direct activation of PKA or EPAC using selective agonists triggered MEC contraction. We conclude that cAMP agonists modulate lacrimal gland MEC contraction via PKA and EPAC activation which also play a major role in OXT induced MEC contraction.

5-HT1B receptors in the basolateral amygdaloid nucleus regulate anxiety-like behaviors through AC-PKA signal pathway in a rat model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is commonly accompanied with anxiety, multiple studies indicate that the basolateral amygdaloid nucleus (BLA) is closely related to modulation of anxiety and expresses serotonin_1B (5-HT_1B) receptors, however, effects of BLA 5-HT_1B receptors on anxiety-like behaviors are unclear, particularly in PD-related anxiety.

METHODS

The open-field and elevated plus maze tests were used to examine anxiety-like behaviors. In vivo electrophysiology and microdialysis were performed to observe the firing activity of BLA neurons and GABA, glutamate, dopamine (DA) and 5-HT release in the BLA, respectively. Western blotting was used to analyze protein expression of 5-HT_1B receptors, adenylate cyclase (AC) and phosphorylated protein kinase A at threonine 197 site (p-PKA-Thr197) in the BLA.

RESULTS

Intra-BLA injection of 5-HT_1B receptor agonist CP93129 produced anxiety-like effects and antagonist SB216641 induced anxiolytic-like responses in sham-operated and 6-hydroxydopamine-lesioned rats. Further, pretreatment with AC inhibitor SQ22536 and PKA inhibitor KT5720 blocked the behavioral effects of CP93129, respectively. Intra-BLA injection of CP93129 increased the firing rate of BLA glutamate neurons and decreased GABA/glutamate ratio and DA and 5-HT levels in the BLA of sham-operated and the lesioned rats, while SB216641 induced the opposite effects. Compared with sham-operated rats, effects of CP93129 and SB216641 on behaviors, electrophysiology and microdialysis were decreased in the lesioned rats, which were associated with decreased expression of 5-HT_1B receptors, AC and p-PKA-Thr197 in the BLA.

CONCLUSION

These findings suggest that 5-HT_1B receptor-AC-PKA signal pathway in the BLA is involved in the regulation of PD-related anxiety.

In silico evolutionary and structural analysis of cAMP response proteins (CARPs) from Leishmania major

With unidentified chemical triggers and novel-effectors, cAMP signaling is broadly noncanonical in kinetoplastida parasites. Though novel protein kinase A regulatory subunits (PKAR) have been identified earlier, cAMP Response Proteins (CARPs) have been identified as a unique and definite cAMP effector of trypanosomatids. CARP1-CARP4 emerged as critical regulatory components of cAMP signaling pathway in Trypanosoma with evidences that CARP3 can directly interact with a flagellar adenylate cyclase (AC). CARP-mediated regulations, identified so far, reflects the mechanistic diversity of cAMP signaling. Albeit the function of the orthologous is not yet delineated, in kinetoplastids like Leishmania, presence of CARP1, 2 and 4 orthologues suggests existence of conserved effector mechanisms. Targeting CARP orthologues in Leishmania, a comprehensive evolutionary analysis of CARPs have been aimed in this study which revealed phylogenetic relationship, codon adaptation and structural heterogeneity among the orthologues, warranting functional analysis in future to explore their involvement in infectivity.

Is Zn2+ the new Ca2+ for TRPC6 channels in the myocardium?

Transient Receptor Potential (TRP) channels are nonselective cation channels, which are mainly permeable to Ca²⁺ and Na⁺ but many of them are also permeable to Zn²⁺. In a new elegant study, a Zn²⁺-dependent pathway involving the TRP member TRPC6 and α1- as well as β-adrenoceptors (AR) was dissected in rodent myocytes. Norepinephrine-mediated activation of α1-AR induces Zn²⁺ influx through TRPC6 channels, which reinforces β-AR-mediated positive inotropy and may help patients with heart failure. This work encourages a closer look at the consequences of Zn²⁺ permeation through TRP channels in human health and disease.

Bordetella parapertussis adenylate cyclase toxin promotes the bacterial survival to the encounter with macrophages

B. parapertussis is a whooping cough etiological agent, whose incidence in the population has increased remarkably. Virulence factors involved in the bacterial infection, however, remain poorly investigated. We here studied the role of adenylate cyclase (CyaA), the main toxin of B. parapertussis, in the outcome of the bacterial interaction with macrophages. Our results showed that B. parapertussis CyaA intoxicates human macrophages, prevents bacterial phagocytosis and precludes phago-lysosomal fusion eventually promoting the bacterial survival to the encounter with these immune cells. Accordingly, we found that B. parapertussis CyaA induces the transcriptional downregulation of host genes encoding for antimicrobial peptides, proteins involved in bacterial intracellular killing, and the pro-inflammatory cytokine TNF-α, while induces the upregulation of the anti-inflammatory cytokine IL-10. Together with previous reports suggesting a protective role of B. parapertussis CyaA against neutrophils bactericidal activity, the results of this study suggest a central role of CyaA in B. parapertussis immune evasion and persistence.

Evolutionary analysis of globin domains from kinetoplastids

Globin (Gb) domains function in sensing gaseous ligands like oxygen and nitric oxide. In recent years, Gb domain containing heme binding adenylate cyclases (OsAC or GbAC) emerged as significant modulator of Leishmania response to hypoxia and oxidative stress. During progression of life cycle stages, kinetoplastids experience altered condition in insect vectors or other hosts. Moreover, marked diversity in life style has been accounted among kinetoplastids. Distribution and abundance of Gb-domains vary between different groups of kinetoplastids. While in bodonoids, Gbs are not combined with any other functional domains, in trypanosomatids it is either fused with adenylate cyclase (AC) or oxidoreductase (OxR) domains. In salivarian trypanosomatids and Leishmania (Viannia) subtypes, no gene product featuring Gbs can be identified. In this context, evolution of Gb-domains in kinetoplastids was explored. GbOxR derived Gbs clustered with bacterial flavohemoglobins (fHb) including one fHb from Advenella, an endosymbiont of monoxeneous trypanosomatids. Codon adaptation and other evolutionary analysis suggested that OsAC (LmjF.28.0090), the solitary Gb-domain featuring gene product in Leishmania, was acquired via possible horizontal gene transfer. Substantial functional divergence was estimated between orthologues of genes encoding GbAC or GbOxR; an observation also reflected in structural alignment and heme-binding residue predictions. Orthologue-paralogue and synteny analysis indicated genomic reduction in GbOxR and GbAC loci for dixeneous trypanosomatids.

Halogen-Dance-Based Synthesis of Phosphonomethoxyethyl (PME) Substituted 2-Aminothiazoles as Potent Inhibitors of Bacterial Adenylate Cyclases

A series of acyclic nucleoside phosphonates (ANPs) was designed as inhibitors of bacterial adenylate cyclases (ACs), where adenine was replaced with 2-amino-4-arylthiazoles. The target compounds were prepared using the halogen dance reaction. Final AC inhibitors were evaluated in cell-based assays (prodrugs) and cell-free assays (phosphono diphosphates). Novel ANPs were potent inhibitors of adenylate cyclase toxin (ACT) from Bordetella pertussis and edema factor (EF) from Bacillus anthracis, with substantial selectivity over mammalian enzymes AC1, AC2, and AC5. Six of the new ANPs were more potent or equipotent ACT inhibitors (IC50 =9-18 nM), and one of them was more potent EF inhibitor (IC50 =12 nM), compared to adefovir diphosphate (PMEApp) with IC50 =18 nM for ACT and IC50 =36 nM for EF. Thus, these compounds represent the most potent ACT/EF inhibitors based on ANPs reported to date. The potency of the phosphonodiamidates to inhibit ACT activity in J774A.1 macrophage cells was somewhat weaker, where the most potent derivative had IC50 =490 nM compared to IC50 =150 nM of the analogous adefovir phosphonodiamidate. The results suggest that more efficient type of phosphonate prodrugs would be desirable to increase concentrations of the ANP-based active species in the cells in order to proceed with the development of ANPs as potential antitoxin therapeutics.

Renin-angiotensin-aldosterone system inhibitors prevent the onset of oxaliplatin-induced peripheral neuropathy: A retrospective multicenter study and in vitro evaluation

Oxaliplatin (OXA) is used in chemotherapy for various cancer types and is associated with acute and chronic neurotoxicity. However, a preventive strategy for OXA-induced peripheral neuropathy (OIPN) and its underlying mechanism remain unclear. We examined the effects of renin-angiotensin-aldosterone system inhibitors (RAASIs) on OIPN by performing a retrospective multicenter study and an in vitro assay. We retrospectively evaluated electronic medical records of 976 patients who underwent one or more courses of OXA-containing regimens at Ehime, Okayama, and Tokushima University Hospitals. The primary endpoint was the incidence of OIPN during or after OXA administration. The effects of RAASIs and OXA on the neurite length in PC12 cells were determined. The combined administration of an OXA-containing regimen and RAASI significantly inhibited the cumulative incidence grade-2 or higher OIPN (log-rank test; P=0.0001). RAASIs markedly suppressed the development of both acute and chronic OIPN (multivariate analysis; P=0.017 and P=0.011). In an in vitro assay, 10 µM OXA suppressed the neurite length; treatment with 1 μM aliskiren, spironolactone, 10 μM candesartan, and enalapril significantly restored neurite length to the control level. Moreover, 1 μM SCH772984 (a selective inhibitor of extracellular signal-regulated kinase, ERK1/2) and 500 μM SQ22536 (a cell-permeable adenylate cyclase [AC] inhibitor) markedly abolished neuroprotective effects of candesartan and enalapril. These results indicate that RAASIs possess preventive or therapeutic effects in acute and chronic OIPN, candesartan and enalapril may directly increase in the activity of ERK1/2 and AC in PC12 cells.

Acyclic nucleoside phosphonates with 2-aminothiazole base as inhibitors of bacterial and mammalian adenylate cyclases

A series of novel acyclic nucleoside phosphonates (ANPs) was synthesized as potential adenylate cyclase inhibitors, where the adenine nucleobase of adefovir (PMEA) was replaced with a 5-substituted 2-aminothiazole moiety. The design was based on the structure of MB05032, a potent and selective inhibitor of fructose 1,6-bisphosphatase and a good mimic of adenosine monophosphate (AMP). From the series of eighteen novel ANPs, which were prepared as phosphoroamidate prodrugs, fourteen compounds were potent (single digit micromolar or submicromolar) inhibitors of Bordetella pertussis adenylate cyclase toxin (ACT), mostly without observed cytotoxicity in J774A.1 macrophage cells. Selected phosphono diphosphates (nucleoside triphosphate analogues) were potent inhibitors of ACT (IC50 as low as 37 nM) and B. anthracis edema factor (IC50 as low as 235 nM) in enzymatic assays. Furthermore, several ANPs were found to be selective mammalian AC1 inhibitors in HEK293 cell-based assays (although with some associated cytotoxicity) and one compound exhibited selective inhibition of mammalian AC2 (only 12% of remaining adenylate cyclase activity) but no observed cytotoxicity. The mammalian AC1 inhibitors may represent potential leads in development of agents for treatment of human inflammatory and neuropathic pain.

Improved adenylate cyclase activity via affinity immobilization onto co-modified GO with bio-inspired adhesive and PEI

Adenylate cyclase (AC) can efficiently catalyze the conversion of adenosine triphosphate (ATP) to cyclic adenosine-3', 5'-monophosphate (cAMP). However, AC directly immobilized on substrate is not desirable due to enzyme inactivation. Herein, bio-inspired adhesive of polydopamine and polyethyleneimine (PDA/PEI) was used as flexible chains to graft on graphene oxide (GO), and the AC was directionally immobilized through affinity between metal ions and his-tags of AC. The properties of modified GO and the activity of immobilized AC were studied in detail. PDA/PEI layers have been proved to improve the amino density of GO surface for affinity groups decoration and adjust the interaction between AC and support. And modified GO by this novel method contributes to subsequent grafting and immobilization of AC by affinity. AC immobilized on modified GO exhibited high activity recovery with about 90 % of free AC, while enzyme immobilized on unmodified GO has been inactivated. This study offers a versatile approach for support modification and enzyme oriented immobilization. PDA/PEI functionalized GO can be used as a promising carrier to immobilize other his-tagged enzymes.

cAMP activates calcium signalling via phospholipase C to regulate cellulase production in the filamentous fungus Trichoderma reesei

BACKGROUND

The filamentous fungus Trichoderma reesei is one of the best producers of cellulase and has been widely studied for the production of cellulosic ethanol and bio-based products. We previously reported that Mn²⁺ and N,N-dimethylformamide (DMF) can stimulate cellulase overexpression via Ca²⁺ bursts and calcium signalling in T. reesei under cellulase-inducing conditions. To further understand the regulatory networks involved in cellulase overexpression in T. reesei, we characterised the Mn²⁺/DMF-induced calcium signalling pathway involved in the stimulation of cellulase overexpression.

RESULTS

We found that Mn²⁺/DMF stimulation significantly increased the intracellular levels of cAMP in an adenylate cyclase (ACY1)-dependent manner. Deletion of acy1 confirmed that cAMP is crucial for the Mn²⁺/DMF-stimulated cellulase overexpression in T. reesei. We further revealed that cAMP elevation induces a cytosolic Ca²⁺ burst, thereby initiating the Ca²⁺ signal transduction pathway in T. reesei, and that cAMP signalling causes the Ca²⁺ signalling pathway to regulate cellulase production in T. reesei. Furthermore, using a phospholipase C encoding gene plc-e deletion strain, we showed that the plc-e gene is vital for cellulase overexpression in response to stimulation by both Mn²⁺ and DMF, and that cAMP induces a Ca²⁺ burst through PLC-E.

CONCLUSIONS

The findings of this study reveal the presence of a signal transduction pathway in which Mn²⁺/DMF stimulation produces cAMP. Increase in the levels of cAMP activates the calcium signalling pathway via phospholipase C to regulate cellulase overexpression under cellulase-inducing conditions. These findings provide insights into the molecular mechanism of the cAMP-PLC-calcium signalling pathway underlying cellulase expression in T. reesei and highlight the potential applications of signal transduction in the regulation of gene expression in fungi.

Involvement of adenylate cyclase/cAMP/CREB and SOX9/MITF in melanogenesis to prevent vitiligo

Vitiligo is autoimmune, acquired, idiopathic, chronic, and progressive de/hypopigmentary cutaneous condition that targets the cell-producing pigment called melanin. It binds to a thread of great disappointment and emotional stress in societies. Combining multiple stress-related theories like toxic compound accumulation, autoimmunity, mutations, altered cellular environment, infection, impaired migration/proliferation, and immunological mismatch of anti-melanocyte and self-reactive T-cells that cause melanocytes damage is formulated resulting in vitiligo. Vitiligo has an orphan status for drug synthesis. Still, different therapies are available, with topical steroids and narrow-band ultraviolet-B monotherapy being the most common treatments, others including medical, physical, or surgical, but not effective. Each modality has its baggage of disadvantages and side effects. Stimulation of the transcriptional process for melanogenesis is mainly achieved by the cAMP-dependent activation of several melanogenic genes by MITF. In this review, we summarized that cAMP encourages the expression of the enzyme tyrosinase, TYRP1, TYRP2, and most other biological effects of cAMP are mediated through the cAMP-dependent PKA pathway resulting in CREB phosphorylation. It has been shown that TYRP1 and 2 do not have cAMP response elements (CREs) in promoting regions; the regulation of these genes by cAMP occurs through the direct participation of MITF during melanogenesis. The available medicines, therefore, only provide symptomatic relief, but do not stop the disease progression. In addition, the treatment process needs to be changed; existing approaches need to be overlooked for patients who are suffering and therefore analyze its efficacy and safety to achieve a favorable risk-benefit ratio.

Comprehensive gene expression profiling of human astrocytes treated with a hepatic encephalopathy-inducible factor, alpha 1-antichymotripsin

Astrocytes are major glial cells that play a critical role in brain homeostasis. Abnormalities in astrocytic function, such as hepatic encephalopathy (HE) during acute liver failure, can result in brain death following brain edema and the associated astrocyte swelling. Recently, we have identified alpha 1-antichymotripsin (ACT) to be a biomarker candidate for HE. ACT induces astrocyte swelling by upregulating aquaporin 4 (AQP4); however, the causal connection between these proteins is not clear yet. In this study, we utilized a microarray profile to screen the differentially expressed genes (DEGs) in astrocytes treated with ACT. We then performed Gene Ontology, REACTOME, and the comprehensive resource of mammalian protein complexes (CORUM) enrichment analyses of the identified DEGs. The results of these analyses indicated that the DEGs were enriched in pathways activating adenylate cyclase (AC)-coupled G protein-coupled receptors (GPCRs) and therefore were involved in the cyclic adenosine monophosphate (cAMP) signaling. These results indicate that ACT may act as a ligand of Gs-GPCRs and subsequently upregulate cAMP. As cAMP is known to upregulate AQP4 in astrocytes, these results suggest that ACT may upregulate AQP4 by activating AC GPCRs and therefore serve as a therapeutic target for acute HE.

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The expression of AQP4 is induced by alpha 1-antichymotripsin dependent activation of adenylate cyclase.

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Combination treatment of alpha 1-antichymotripsin and arginine vasopressin enhance the activation of adenylate cyclase.

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Alpha 1-antichemotripsin might be a therapeutic target for acute hepatic encephalopathy.

cAMP levels regulate macrophage alternative activation marker expression

The capacity for macrophages to polarize into distinct functional activation states (e.g., M1, M2) is critical to tune an inflammatory response to the relevant infection or injury. Alternative or M2 polarization of macrophages is most often achieved in vitro in response to IL-4/IL-13 and results in the transcriptional up-regulation of a constellation of characteristic M2 marker genes. In vivo, additional signals from the inflammatory milieu can further increase or decrease M2 marker expression. Particularly, activation of cAMP-generating G protein-coupled receptors is reported to increase M2 markers, but whether this is strictly dependent upon cAMP production is unclear. We report herein that increased cAMP alone can increase IL-4-dependent M2 marker expression through a PKA/C/EBPβ/CREB dependent pathway in murine macrophages.

Regulatory molecule cAMP changes cell fitness of the engineered Escherichia coli for terpenoids production

Terpenoids are a class of natural compounds with many important functions and applications. They are synthesized from a long synthetic pathway of isoprenyl unit coupling with the myriads of terpene synthases. Owing to the catalytic divergence of terpenoids synthesis, microbial production of terpenoids is compromised to the complexity of pathway engineering and suffers from the metabolic engineering burden. In this work, the adaptive Escherichia coli HP variant exhibited a general cell fitness in terpenoid synthesis. Especially, it could yield taxadiene of 193.2 mg/L in a test tube culture, which is a five-fold increase over the production in the wild type E. coli DH5α. Mutational analyses indicated that IS10 insertion in adenylate cyclase CyaA (CyaA_HP) resulted in lowering intracellular cyclic AMP (cAMP), which could regulate its receptor protein CRP to rewire cell metabolism and contributed to the improved cell fitness. Our results suggested a way to manipulate cell fitness for terpenoids production and other products.

Does high on-treatment platelet aggregability reflect poor individual response to clopidogrel?

INTRODUCTION

On-treatment platelet aggregability represents the major form of functional assessment for patients treated with P2Y₁₂ receptor antagonists, with "high" on-treatment platelet aggregability (HTPA) predicting thrombotic risk. However HTPA reflects a variable combination of pre-treatment hyperaggregability and poor response to P2Y₁₂ antagonists. We have previously shown that integrity of platelet adenylate cyclase/cAMP signaling, assessed with PGE₁, is a strong predictor of individual responses to clopidogrel. We therefore sought to determine the extent to which HTPA reflects impaired platelet responsiveness to clopidogrel.

METHODS

Using data from our previous investigations of acute and sub-acute effects of clopidogrel, we analyzed the relationship between on-treatment aggregability and acute/steady state responsiveness to clopidogrel, utilizing ADP, the thromboxane A₂ mimetic U46619, and thrombin receptor-activating peptide (TRAP) as pro-aggregants. The relationship between anti-aggregatory response to PGE₁ and both on-treatment and pre-treatment aggregability was also examined.

RESULTS AND CONCLUSIONS

With all 3 pro-aggregants, (1) response to clopidogrel after 4 h, as measured by ΔADP response, exhibits a strong inverse relationship with on-treatment aggregation, with a similarly inverse relationship between pre-treatment PGE₁ response and on-treatment aggregability; (2) there is a weaker inverse relationship between clopidogrel response and pre-treatment platelet aggregability, and a significant inverse relationship between pre-treatment PGE₁ response and pre-treatment platelet aggregability. Furthermore, pre-treatment PGE₁ response also predicts on-treatment platelet aggregability in response to ADP at steady state. Thus, HTPA largely represents clopidogrel resistance.

Roles of Adenylate Cyclases in Ciliary Responses of Paramecium to Mechanical Stimulation

Paramecium shows rapid forward swimming due to increased beat frequency of cilia in normal (forward swimming) direction in response to various kinds of stimuli applied to the cell surface that cause K⁺ -outflow accompanied by a membrane hyperpolarization. Some adenylate cyclases are known to be functional K⁺ channels in the membrane. Using gene-specific knockdown methods, we examined nine paralogues of adenylate cyclases in P. tetraurelia to ascertain whether and how they are involved in the mechanical stimulus-induced hyperpolarization-coupled acceleration of forward swimming. Results demonstrated that knockdown of the adenylate cyclase 1 (ac1)-gene and 2 (ac2)-gene inhibited the acceleration of forward swimming in response to mechanical stimulation of the cell, whereas that spared the acceleration response to external application of 8-Br-cAMP and dilution of extracellular [K⁺ ] induced hyperpolarization. Electrophysiological examination of the knockdown cells revealed that the hyperpolarization-activated inward K⁺ current is smaller than that of a normal cell. Our results suggest that AC1 and AC2 are involved in the mechanical stimulus-induced acceleration of ciliary beat in Paramecium.

G-protein βγ subunits as multi-functional scaffolds and transducers in G-protein-coupled receptor signaling

G-protein βγ subunits are key participants in G-protein signaling. These subunits facilitate interactions between receptors and G proteins that are critical for the G protein activation cycle at the plasma membrane. In addition, they play roles in directly transducing signals to an ever expanding range of downstream targets, including integral membrane and cytosolic proteins. Emerging data indicate that Gβγ may play additional roles at intracellular compartments including endosomes, the Golgi apparatus, and the nucleus. Here, we discuss the molecular and structural basis for their ability to coordinate this wide range of cellular activities.

Overexpression of the adenylate cyclase gene cyaC facilitates current generation by Shewanella oneidensis in bioelectrochemical systems

Electrochemically active bacteria (EAB) are capable of electrochemical interactions with electrodes via extracellular electron transfer (EET) pathways and serve as essential components in bioelectrochemical systems. Previous studies have suggested that EAB, such as Shewanella oneidensis MR-1, use cyclic AMP (cAMP) receptor proteins to coordinately regulate the expression of catabolic and EET-related genes, prompting us to hypothesize that the intracellular cAMP concentration is an important factor determining the electrochemical activities of EAB. The present study constructed an MR-1 mutant, cyaC-OE, that overexpressed cyaC, a gene encoding a membrane-bound class III adenylate cyclase, and examined its electrochemical and transcriptomic characteristics. We show that the intracellular cAMP concentration in cyaC-OE is more than five times that in wild-type MR-1, and that cya-OE generates approximately two-fold higher current in BES than the wild-type strain. In addition, the expression of genes involved in EET and anaerobic carbon catabolism is up-regulated in cya-OE compared to that in the wild-type strain. These results suggest that increasing the intracellular cAMP level is a promising approach for constructing EAB with high catabolic and electrochemical activities.

Therapeutic opportunities in colon cancer: Focus on phosphodiesterase inhibitors. Life Sci. 2019;230:150-161. [PMID: 31125564 DOI: 10.1016/j.lfs.2019.05.043]

Despite novel technologies, colon cancer remains undiagnosed and 25% of patients are diagnosed with metastatic colon cancer. Resistant to chemotherapeutic agents is one of the major problems associated with treating colon cancer which creates the need to develop novel agents targeting towards newer targets. A phosphodiesterase is a group of isoenzyme, which, hydrolyze cyclic nucleotides and thereby lowers intracellular levels of cAMP and cGMP leading to tumorigenic effects. Many in vitro and in vivo studies have confirmed increased PDE expression in different types of cancers including colon cancer. cAMP-specific PDE inhibitors increase intracellular cAMP that leads to activation of effector molecules-cAMP-dependent protein kinase A, exchange protein activated by cAMP and cAMP gated ion channels. These molecules regulate cellular responses and exert its anticancer role through different mechanisms including apoptosis, inhibition of angiogenesis, upregulating tumor suppressor genes and suppressing oncogenes. On the other hand, cGMP specific PDE inhibitors exhibit anticancer effects through cGMP dependent protein kinase and cGMP dependent cation channels. Elevation in cGMP works through activation of caspases, suppression of Wnt/b-catenin pathway and TCF transcription leading to inhibition of CDK and survivin. These studies point out towards the fact that PDE inhibition is associated with anti-proliferative, anti-apoptotic and anti-angiogenic pathways involved in its anticancer effects in colon cancer. Thus, inhibition of PDE enzymes can be used as a novel approach to treat colon cancer. This review will focus on cAMP and cGMP signaling pathways leading to tumorigenesis and the use of PDE inhibitors in colon cancer.

The adenylate cyclase UvAc1 and phosphodiesterase UvPdeH control the intracellular cAMP level, development, and pathogenicity of the rice false smut fungus Ustilaginoidea virens

The cyclic adenosine monophosphate (cAMP) signaling pathway plays pleiotropic roles in regulating development and pathogenicity in eukaryotes. cAMP is a second messenger that is important for the activation of downstream pathways. The intracellular cAMP level is modulated mainly by its biosynthesis, which is catalyzed by adenylate cyclases (ACs), and hydrolysis by phosphodiesterases (PDEs). Here, we identified the AC UvAc1 and the cAMP high-affinity PDE UvPdeH in the rice false smut fungus Ustilaginoidea virens; these enzymes are homologs of MoMac1 and MoPdeH in Magnaporthe oryzae (rice blast fungus). A heterogenous complementation assay revealed that UvAc1 and UvPdeH partially or completely rescued the defects in ΔMomac1 and ΔMopdeH mutant M. oryzae. UvAc1 and UvPdeH play important roles in the development and virulence of U. virens. ΔUvac1 and ΔUvpdeH mutant fungi showed defects in conidial production, morphology, and germination; reduced toxicity against germinating rice seeds; and reduced virulence on rice panicles. ΔUvac1 exhibited increased sensitivity to Calcofluor White (CFW) and sodium chloride (NaCl), and decreased sensitivity to Congo Red (CR), while ΔUvpdeH showed increased sensitivity to sodium dodecyl sulfate, CR, sorbitol, and hydrogen peroxide, and decreased sensitivity to CFW and NaCl. High-performance liquid chromatography revealed that the intracellular cAMP level was significantly increased in ΔUvpdeH and decreased in ΔUvac1. Taken together, our results demonstrate that UvAc1 and UvPdeH are conservative components of the cAMP pathway that are important for conidiogenesis, stress responses, virulence, and regulation of the intracellular cAMP level in U. virens.

In search of a function for the membrane anchors of class IIIa adenylate cyclases

Nine pseudoheterodimeric mammalian adenylate cyclases possess two dissimilar hexahelical membrane domains (TM1 and TM2), two dissimilar cyclase-transducing-elements (CTEs) and two complementary catalytic domains forming a catalytic dimer (often termed cyclase-homology-domain, CHD). Canonically, these cyclases are regulated by G-proteins which are released upon ligand activation of G-protein-coupled receptors. So far, a biochemical function of the membrane domains beyond anchoring has not been established. For almost 30 years, work in our laboratory was based on the hypothesis that these voluminous membrane domains possess an additional physiological, possibly regulatory function. Over the years, we have generated numerous artificial fusion proteins between the catalytic domains of various bacterial adenylate cyclases which are active as homodimers and the membrane receptor domains of known bacterial signaling proteins such as chemotaxis receptors and quorum-sensors which have known ligands. Here we summarize the current status of our experimental efforts. Taken together, the data allow the conclusion that the hexahelical mammalian membrane anchors as well as similar membrane anchors from bacterial adenylate cyclase congeners are orphan receptors. A search for as yet unknown ligands of membrane-delimited adenylate cyclases is now warranted.

Role of cAMP modulator supplementations during oocyte in vitro maturation in domestic animals

Cyclic adenosine monophosphate (cAMP) is an important molecule in signal transduction within the cell, functioning as a second cell messenger of gonadotrophin stimulation. The concentration of cAMP in cumulus-oocyte complexes (COCs) is known to be controlled through modulation of its synthesis by adenylyl cyclase (AC) and by degradation through the cyclic nucleotide phosphodiesterase (PDE) enzymes. One of the main obstacles for in vitro embryo production is the optimization of reproduction processes that occur in oocyte maturation. The function of cAMP is important in maintaining meiotic arrest in mammalian oocytes. When the oocyte is physically removed from the antral follicle for in vitro maturation (IVM), intra-oocyte cAMP concentrations decrease and spontaneous meiotic resumption begins, due to the depletion of inhibitory factors from the follicle. In many studies, relatively greater cAMP concentrations before IVM has been reported to improve oocyte competence, leading to subsequent benefits in embryonic development in different species. There, therefore, has been an increase in oocyte cAMP concentrations with several treatments and different approaches, such as invasive AC, stimulators of AC activity, PDE inhibitors, and cAMP analogs. The aim of this review is to comprehensively evaluate and provide data related to (i) the use of cAMP modulators during IVM and the effects on completion of meiosis and cytoplasmic reorganization, which are required for development of oocytes with the capacity to contribute to fertilization and subsequent embryonic development; and (ii) the main cAMP modulators and the effects when used in oocyte IVM.

Modulation of adenylate cyclase signaling in association with MKK3/6 stabilization under combination of SAC and berberine to reduce HepG2 cell survivability

Cancer cells often have faulty apoptotic pathways resulting in sustenance of survivability, tumour metastasis and resistance to anticancer drugs. Alternate strategies are sought to improve therapeutic efficacy and therefore HepG2 cells were treated with S-allyl-cysteine (SAC) and berberine (BER) to analyze their mechanistic impact upon necroptosis along with its interacting relationship to apoptosis. In the present study we observed that SAC and BER exposure reduced NFκβ nuclear translocation through adenylate cyclase-cAMP-protein kinaseA axis and eventually evaded c-FLIP inhibition. Effective RIP1 k63-polyubiquitination and persistent MKK3/MKK6 expression during drug treatment potentiated caspase8 activity via p53-DISC conformation. Resultant tBid associated lysosomal protease mediated AIF truncation induced DNA fragmentation and persuaded effector caspase mediated scramblase activation resulting induction of necroptosis in parallel to apoptotic events. SAC+BER effectively reduced Rb-phosphorylation resulting insignificant nuclear E2F presence led to ending of cell proliferation. Therefore necroptosis augmented the drug response and may be targeted alongside cell proliferation inhibition in formation of efficient therapeutics against liver cancer.

Effector Translocation: Cya Reporter Assay

An accurate and complete roster of the Type III effector (T3E) proteins translocated by the P. syringae Type III secretion system (T3SS) into host cells is critical to understanding the pathogen's interactions with plants. The adenylate cyclase (Cya) reporter offers a highly sensitive and robust assay for monitoring the translocation of T3Es. T3Es are fused to the calmodulin-dependent adenylate-cyclase domain of CyaA. The T3E targets Cya for translocation through the T3SS into the host cell at which point it is activated by calmodulin and converts adenosine triphosphate into cyclic adenosine monophosphate (cAMP). The T3SS translocation-dependent increase in cAMP concentration in plant cells is then measured with an enzyme-linked immunosorbent assay kit. The Cya reporter can be used to determine whether a candidate protein is translocated by T3SS or to measure relative levels of T3SS translocation in a semiquantitative manner.

Affinity induced immobilization of adenylate cyclase from the crude cell lysate for ATP conversion

The development of an orientation immobilization technique via affinity between polyhistidine tags and metal ions aims at maintaining biocatalytic activity of the enzymes. In this work, to tackle the issue of the immobilization of adenylate cyclase (AC), a simple and effective approach of synthesizing iminodiacetic acid (IDA)-Ni²⁺ particles was applied for simultaneously purifying and immobilizing his-tagged AC. We chose agarose particles as carriers, and then decorated them with IDA, leading to the formation of a coordination combination of Ni²⁺. The porous carriers with a large pore size of 50 nm and a specific surface area of 45.8 m²/g exhibited favorable enzymatic activity and loading capacity. The optimal pH of the immobilized enzyme increased from 8.0 to 9.0 and the optimal temperature increased from 30 °C to 35 °C, compared to the free AC. Moreover, the immobilized AC retained a residual activity of approximately 80% after storing it at 25 °C for 48 h, whereas only 40% of the activity was left in the free AC at the same conditions. Maximum yield of cyclic adenosine-3', 5'- monophosphate (cAMP) reached up to the summit of the reaction. The immobilized AC by affinity adsorption will provide a promising route for the industrial production of cAMP.

A Bacterial Adenylate Cyclase-Based Two-Hybrid System Compatible with Gateway® Cloning

The bacterial adenylate cyclase two-hybrid system (BACTH) is a genetic approach used to test protein interactions in vivo in E. coli. This system takes advantage of the two catalytic domains of Bordetella pertussis adenylate cyclase (CyaA) toxin, which can be fused separately to proteins of interest. If the proteins of interest interact, then the adenylate cyclase domains will be brought in close proximity to each other, reconstituting cyclic AMP (cAMP) production. Interacting proteins can be both qualitatively and quantitatively assessed by the expression of chromosomal genes of the E. coli lac or mal operon, which are positively regulated by cAMP production. Because cAMP is diffusible, the proteins of interest do not need to interact near the transcriptional machinery. Consequently, both cytosolic and membrane protein-protein interactions can be tested. The BACTH system has recently been modified to be compatible with Gateway® recombinational cloning, BACTHGW. This chapter explains the principle of the BACTH, its Gateway® modified system, and details of the general procedure.

Cyclic Nucleotide Monophosphates in Plants and Plant Signaling

Cyclic nucleotide monophosphates (cNMPs) and the enzymes that can generate them are of increasing interest in the plant sciences. Arguably, the major recent advance came with the release of the complete Arabidopsis thaliana genome that has enabled the systematic search for adenylate (ACs) or guanylate cyclases (GCs) and did eventually lead to the discovery of a number of GCs in higher plants. Many of these proteins have complex domain architectures with AC or GC centers moonlighting within cytosolic kinase domains. Recent reports indicated the presence of not just the canonical cNMPs (i.e., cAMP and cGMP), but also the noncanonical cCMP, cUMP, cIMP, and cdTMP in plant tissues, and this raises several questions. Firstly, what are the functions of these cNMPs, and, secondly, which enzymes can convert the substrate triphosphates into the respective noncanonical cNMPs? The first question is addressed here by comparing the reactive oxygen species (ROS) response of cAMP and cGMP to that elicited by the noncanonical cCMP or cIMP. The results show that particularly cIMP can induce significant ROS production. To answer, at least in part, the second question, we have evaluated homology models of experimentally confirmed plant GCs probing the substrate specificity by molecular docking simulations to determine if they can conceivably catalytically convert substrates other than ATP or GTP. In summary, molecular modeling and substrate docking simulations can contribute to the evaluation of cyclases for noncanonical cyclic mononucleotides and thereby further our understanding of the molecular mechanism that underlie cNMP-dependent signaling in planta.

Understanding the Mechanism of Translocation of Adenylate Cyclase Toxin across Biological Membranes

Adenylate cyclase toxin (ACT) is one of the principal virulence factors secreted by the whooping cough causative bacterium Bordetella pertussis, and it has a critical role in colonization of the respiratory tract and establishment of the disease. ACT targets phagocytes via binding to the CD11b/CD18 integrin and delivers its N-terminal adenylate cyclase (AC) domain directly to the cell cytosol, where it catalyzes unregulated conversion of cytosolic ATP into cAMP upon activation by binding to cellular calmodulin. High cAMP levels disrupt bactericidal functions of the immune cells, ultimately leading to cell death. In spite of its relevance in the ACT biology, the mechanism by which its ≈400 amino acid-long AC domain is transported through the target plasma membrane, and is released into the target cytosol, remains enigmatic. This article is devoted to refresh our knowledge on the mechanism of AC translocation across biological membranes. Two models, the so-called "two-step model" and the recently-proposed "toroidal pore model", will be considered.

Piperonal attenuates visceral adiposity in mice fed a high-fat diet: potential involvement of the adenylate cyclase-protein kinase A dependent pathway

SCOPE

Piperonal is an aromatic compound found in vanilla and has a floral odor resembling vanillin. This study was aimed to test whether piperonal attenuates visceral adiposity induced by a high-fat diet (HFD) in mice and to explore the underlying molecular mechanisms.

METHODS AND RESULTS

Male C57BL/6N mice were fed a normal diet, HFD, or 0.05% piperonal-supplemented HFD (PSD) for 10 weeks. PSD-fed mice showed attenuation of body weight gain, total visceral fat pad weights, and plasma lipid levels compared to HFD-fed mice. Piperonal supplementation of the HFD increased the mRNA expression of certain isotypes of adenylate cyclase (Adcy) and protein kinase A (PKA) in the white adipose tissue (WAT) of mice. The adipogenesis-related genes were downregulated, whereas fatty acid oxidation- and thermogenesis-related genes were upregulated in the WAT of PSD-fed mice compared to those in HFD-fed mice. Piperonal directly activated Adcy by decreasing the K_m for its substrate (ATP) in plasma membranes prepared from the WAT of mice. Furthermore, piperonal-induced inhibition of adipocyte differentiation and elevation of Adcy and PKA activities in 3T3-L1 cells were abrogated by an Adcy inhibitor.

CONCLUSION

The anti-adipogenic effect of piperonal in mice fed the high-fat diet appears to be associated with increased Adcy-PKA signaling in WAT.

Eye and heart morphogenesis are dependent on melatonin signaling in chick embryos

Calmodulin is vital for chick embryos morphogenesis in the incubation time 48-66 h when the rudimentary C-shaped heart attains an S-shaped pattern and the optic vesicles develop into optic cups. Melatonin is in the extraembryonic yolk sac of the avian egg; melatonin binds calmodulin. The aim of this study was to investigate the function of melatonin in the formation of the chick embryo optic cups and S-shaped heart, by pharmacological methods and immunoassays. Mel1a melatonin receptor immunofluorescence was distributed in the optic cups and rudimentary hearts. We separated embryonated chicken eggs at 48 h of incubation into basal, control and drug-treated groups, with treatment applied in the egg air sac. At 66 h of incubation, embryos were excised from the eggs and analyzed. Embryos from the basal, control (distilled water), melatonin and 6-chloromelatonin (melatonin receptor agonist) groups had regular optic cups and an S-shaped heart, while those from the calmidazolium (calmodulin inhibitor) group did not. Embryos from the luzindole (melatonin receptor antagonist) and prazosin (Mel1c melatonin receptor antagonist) groups did not have regular optic cups. Embryos from the 4-P-PDOT (Mel1b melatonin receptor antagonist) group did not have an S-shaped heart. Previous application of the melatonin, 6-chloromelatonin or forskolin (adenylate cyclase enhancer) prevented the abnormal appearance of chick embryos from the calmidazolium, luzindole, prazosin and 4-P-PDOT groups. However, 6-chloromelatonin and forskolin only partially prevented the development of defective eye cups in embryos from the calmidazolium group. The results suggested that melatonin modulates chick embryo morphogenesis via calmodulin and membrane receptors.

Exposure to Bordetella pertussis adenylate cyclase toxin affects integrin-mediated adhesion and mechanics in alveolar epithelial cells

BACKGROUND INFORMATION

The adenylate cyclase (CyaA) toxin is a major virulent factor of Bordetella pertussis, the causative agent of whooping cough. CyaA toxin is able to invade eukaryotic cells where it produces high levels of cyclic adenosine monophosphate (cAMP) affecting cellular physiology. Whether CyaA toxin can modulate cell matrix adhesion and mechanics of infected cells remains largely unknown.

RESULTS

In this study, we use a recently proposed multiple bond force spectroscopy (MFS) with an atomic force microscope to assess the early phase of cell adhesion (maximal detachment and local rupture forces) and cell rigidity (Young's modulus) in alveolar epithelial cells (A549) for toxin exposure <1 h. At 30 min of exposure, CyaA toxin has a minimal effect on cell viability (>95%) at CyaA concentration of 0.5 nM, but a significant effect (≈81%) at 10 nM. MFS performed on A549 for three different concentrations (0.5, 5 and 10 nM) demonstrates that CyaA toxin significantly affects both cell adhesion (detachment forces are decreased) and cell mechanics (Young's modulus is increased). CyaA toxin (at 0.5 nM) assessed at three indentation/retraction speeds (2, 5 and 10 μm/s) significantly affects global detachment forces, local rupture events and Young modulus compared with control conditions, while an enzymatically inactive variant CyaAE5 has no effect. These results reveal the loading rate dependence of the multiple bonds newly formed between the cell and integrin-specific coated probe as well as the individual bond kinetics which are only slightly affected by the patho-physiological dose of CyaA toxin. Finally, theory of multiple bond force rupture enables us to deduce the bond number N which is reduced by a factor of 2 upon CyaA exposure (N ≈ 6 versus N ≈ 12 in control conditions).

CONCLUSIONS

MFS measurements demonstrate that adhesion and mechanical properties of A549 are deeply affected by exposure to the CyaA toxin but not to an enzymatically inactive variant. This indicates that the alteration of cell mechanics triggered by CyaA is a consequence of the increase in intracellular cAMP in these target cells.

SIGNIFICANCE

These results suggest that mechanical and adhesion properties of the cells appear as pertinent markers of cytotoxicity of CyaA toxin.

Protein kinase A inhibition facilitates the antitumor activity of xanthohumol, a valosin-containing protein inhibitor

Xanthohumol (XN), a simple prenylated chalcone, can be isolated from hops and has the potential to be a cancer chemopreventive agent against several human tumor cell lines. We previously identified valosin‐containing protein (VCP) as a target of XN; VCP can also play crucial roles in cancer progression and prognosis. Therefore, we investigated the molecular mechanisms governing the contribution of VCP to the antitumor activity of XN. Several human tumor cell lines were treated with XN to investigate which human tumor cell lines are sensitive to XN. Several cell lines exhibited high sensitivity to XN both in vitro and in vivo. shRNA screening and bioinformatics analysis identified that the inhibition of the adenylate cyclase (AC) pathway synergistically facilitated apoptosis induced by VCP inhibition. These results suggest that there is crosstalk between the AC pathway and VCP function, and targeting both VCP and the AC pathway is a potential chemotherapeutic strategy for a subset of tumor cells.

Role of leishmanial acidocalcisomal pyrophosphatase in the cAMP homeostasis in phagolysosome conditions required for intra-macrophage survival

Exposure of Leishmania donovani to macrophage phagolysosome conditions (PC) (37°C and pH 5.5) led to increased intracellular cAMP and cAMP-mediated responses, which help in intra-macrophage survival pre-requisite for infectivity. In the absence of typical orthologs for G-proteins and G-protein coupled receptors, we sought to study the precise mechanisms for positive modulation of cAMP production during exposure to PC. Amongst two promastigote-stage specific membrane bound receptor adenylate cyclases (LdRAC-A and LdRAC-B), LdRAC-A appeared to function as a major cAMP generator following PC exposure. Pyrophosphate (PPi), an energy storage compound as well as a by-product of cAMP biosynthesis by adenylate cyclise, was found to be decreased following PC exposure. This may be due to microtubule and microfilament-driven translocation of acidocalcisomes near plasma membrane vicinity with concomitant increase of acidocalcisome membrane pyrophosphatase (LdV-H⁺PPase) and acidocalcisomal soluble pyrophosphatase (LdVSP1). Episomal over-expression and conditional silencing demonstrated regulatory role of V-H⁺PPase on cAMP trigger and consequent induction of resistance to macrophage-derived pro-oxidants and parasite killing. Furthermore, immunofluorescence analysis revealed possible co-localization of LdV-H⁺PPase and LdRAC-A during PC exposure. Collectively, these results suggest that translocation of acidocalcisome in membrane vicinity functions as a trigger for LdRAC-A-driven cAMP generation through depletion of PPi pool by LdV-H⁺PPase.

New Developments in Platelet Cyclic Nucleotide Signalling: Therapeutic Implications

Altered platelet physiology may contribute to the emergence of thrombosis in patients with many forms of cardiovascular disease. Excess platelet activation may reflect increased stimulation of pro-aggregatory pathways. There is, however, increasing evidence that excessive platelet response, due to impaired efficacy of anti-aggregatory autacoids such as nitric oxide (NO) and prostacyclin (PGI₂), may be just as important. For example, diminished platelet response to NO has been documented in acute and chronic myocardial ischaemia, heart failure, aortic valve disease and in the presence of hyperglycaemia. This "NO resistance" has been shown to reflect both the scavenging of NO by reactive oxygen species and dysfunction of its intracellular "receptor", soluble guanylate cyclase. Importantly, these abnormalities of NO signalling are potentially reversible through judicious application of pharmacotherapy. The analogous condition of impaired PGI₂/adenylate cyclase (AC) signalling has received comparatively less attention to date. We have shown that platelet response to prostaglandin E₁ (PGE₁) is frequently impaired in patients with symptomatic myocardial ischaemia. Because the effects of ADP receptor antagonists such as clopidogrel and ticagrelor at the level of the P2Y₁₂ receptor are coupled with changes in activity of AC, impaired response to PGE₁ might imply both increased thrombotic risk and a reduced efficacy of anti-aggregatory drugs. Accordingly, patient response to treatment with clopidogrel is determined not only by variability of clopidogrel bio-activation, but also extensively by the integrity of platelet AC signalling. We here review these recent developments and their emerging therapeutic implications for thrombotic disorders.

Low reversibility of intracellular cAMP accumulation in mouse Leydig tumor cells (MLTC-1) stimulated by human Luteinizing Hormone (hLH) and Chorionic Gonadotropin (hCG)

In order to study the intracellular cAMP response kinetics of Leydig cells to hormones with LH activity, we used MLTC-1 cells transiently expressing a chimeric cAMP-responsive luciferase so that real-time variations of intracellular cAMP concentration could be followed using oxiluciferin luminescence produced from catalyzed luciferin oxidation. The potencies of the different LHs and CGs were evaluated using areas under the curves (AUC) of their kinetics over 60 min stimulation. All mammalian LHs and CGs tested were found to stimulate cAMP accumulation in these cells. The reversibility of this stimulation was studied by removing the hormone from the culture medium after 10 min of incubation. The ratios of kinetics AUC after removing or not the hormone were used to evaluate the stimulation reversibility of each hormone. Natural and recombinant hLHs and hCGs were found to exhibit slowly reversible activation compared to pituitary rat, ovine, porcine, camel and equine LHs, serum-derived eCG (PMSG) and recombinant eLH/CGs. Carbohydrate side chains are not involved in this phenomenon since natural and recombinant homologous hormones exhibit the same reversibility rates. It is still unknown whether only one human subunit, α or β, is responsible for this behaviour or whether it is due to a particular feature of the hLH and hCG quaternary structure.

Endogenous occurrence of protein S-guanylation in Escherichia coli: Target identification and genetic regulation

8-Nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP) is a nitrated cGMP derivative formed in response to nitric oxide (NO) and reactive oxygen species (ROS). It can cause a post-translational modification (PTM) of protein thiols through cGMP adduction (protein S-guanylation). Accumulating evidence has suggested that, in mammals, S-guanylation of redox-sensor proteins may implicate in regulation of adaptive responses against ROS-associated oxidative stress. Occurrence as well as protein targets of S-guanylation in bacteria remained unknown, however. Here we demonstrated, for the first time, the endogenous occurrence of protein S-guanylation in Escherichia coli (E. coli). Western blotting using anti-S-guanylation antibody clearly showed that multiple proteins were S-guanylated in E. coli. Interestingly, some of those proteins were more intensely S-guanylated when bacteria were cultured under static culture condition than shaking culture condition. It has been known that E. coli is deficient of guanylate cyclase, an enzyme indispensable for 8-nitro-cGMP formation in mammals. We found that adenylate cyclase from E. coli potentially catalyzed 8-nitro-cGMP formation from its precursor 8-nitroguanosine 5'-triphosphate. More importantly, E. coli lacking adenylate cyclase showed significantly reduced formation of S-guanylated proteins. Our S-guanylation proteomics successfully identified S-guanylation protein targets in E. coli, including chaperons, ribosomal proteins, and enzymes which associate with protein synthesis, redox regulation and metabolism. Understanding of functional impacts for protein S-guanylation in bacterial signal transduction is necessary basis for development of potential chemotherapy and new diagnostic strategy for control of pathogenic bacterial infections.

Intersections at the crossroads: Neurofibromatosis type 1, cAMP, sex, and glioma risk

Cancer predisposition syndromes, particularly neurofibromatosis type 1 (NF1), provide unique vantage points from which to examine the co-contributions of molecular, cellular, and tissue processes to tumor biology. Polymorphisms in adenylate cyclase 8 affect brain tumor risk in NF1 in a sex-specific fashion, illuminating novel interdependencies in brain tumorigenesis.

Adenylate cyclase in Arthrospira platensis responds to light through transcription

Cyclic 3',5' adenosine monophosphate (cAMP) is a ubiquitous signaling molecule, but its role in higher plants was in doubt due to its very low concentration. In this study we wanted to look at the flux of cAMP in response to light in algae, considered to be the more primitive form of photosynthetic organisms. While it did not fluctuate very much in the tested green algae, in the cyanobacterium Arthrospira platensis its level was closely linked to exposure to light. The expression from cyaC, the major isoform of adenylate cyclase was strongly influenced by exposure of the cells to light. There was about 300 fold enhancement of cyaC transcripts in cells exposed to light compared to the transcripts in cells in the dark. Although post-translational regulation of adenylate cyclase activity has been widely known, our studies suggest that transcriptional control could also be an important aspect of its regulation in A. platensis.

Prostaglandin E2 Stimulates EP2, Adenylate Cyclase, Phospholipase C, and Intracellular Calcium Release to Mediate Cyclic Adenosine Monophosphate Production in Dental Pulp Cells

INTRODUCTION

Prostaglandin E2 (PGE2) plays a crucial role in pulpal inflammation and repair. However, its induction of signal transduction pathways is not clear but is crucial for future control of pulpal inflammation.

METHODS

Primary dental pulp cells were exposed to PGE2 and 19R-OH PGE2 (EP2 agonist) or sulprostone (EP1/EP3 agonist) for 5 to 40 minutes. Cellular cyclic adenosine monophosphate (cAMP) levels were measured using the enzyme-linked immunosorbent assay. In some experiments, cells were pretreated with SQ22536 (adenylate cyclase inhibitor), H89 (protein kinase A inhibitor), dorsomorphin (adenosine monophosphate-activated protein kinase inhibitor), U73122 (phospholipase C inhibitor), thapsigargin (inhibitor of intracellular calcium release), W7 (calmodulin antagonist), verapamil (L-type calcium channel blocker), and EGTA (extracellular calcium chelator) for 20 minutes before the addition of PGE2.

RESULTS

PGE2 and 19R-OH PGE2 (EP2 agonist) stimulated cAMP production, whereas sulprostone (EP1/EP3 agonist) shows little effect. PGE2-induced cAMP production was attenuated by SQ22536 and U73122 but not H89 and dorsomorphin. Intriguingly, thapsigargin and W7 prevented PGE2-induced cAMP production, but verapamil and EGTA showed little effect.

CONCLUSIONS

These results indicate that PGE2-induced cAMP production is associated with EP2 receptor and adenylate cyclase activation. These events are mediated by phospholipase C, intracellular calcium release, and calcium-calmodulin signaling. These results are helpful for understanding the role of PGE2 in pulpal inflammation and repair and possible future drug intervention.

Partial Adenosine A1 Agonist in Heart Failure

Adenosine exerts a variety of physiological effects by binding to cell surface G-protein-coupled receptor subtypes, namely, A1, A2a, A2b, and A3. The central physiological role of adenosine is to preclude tissue injury and promote repair in response to stress. In the heart, adenosine acts as a cytoprotective modulator, linking cardiac function to metabolic demand predominantly via activation of adenosine A1 receptors (A1Rs), which leads to inhibition of adenylate cyclase activity, modulation of protein kinase C, and opening of ATP-sensitive potassium channels. Activation of myocardial adenosine A1Rs has been shown to modulate a variety of pathologies associated with ischemic cardiac injury, including arrhythmogenesis, coronary and ventricular dysfunction, apoptosis, mitochondrial dysfunction, and ventricular remodeling. Partial A1R agonists are agents that are likely to elicit favorable pharmacological responses in heart failure (HF) without giving rise to the undesirable cardiac and extra-cardiac effects observed with full A1R agonism. Preclinical data have shown that partial adenosine A1R agonists protect and improve cardiac function at doses that do not result in undesirable effects on heart rate, atrioventricular conduction, and blood pressure, suggesting that these compounds may constitute a valuable new therapy for chronic HF. Neladenoson bialanate (BAY1067197) is the first oral partial and highly selective A1R agonist that has entered clinical development for the treatment of HF. This review provides an overview of adenosine A1R-mediated signaling in the heart, summarizes the results from preclinical and clinical studies of partial A1R agonists in HF, and discusses the potential benefits of these drugs in the clinical setting.

The Arabidopsis thaliana K(+)-uptake permease 7 (AtKUP7) contains a functional cytosolic adenylate cyclase catalytic centre

Adenylate cyclases (ACs) catalyse the formation of the second messenger cyclic adenosine 3',5'-monophosphate (cAMP) from adenosine 5'-triphosphate (ATP). Although cAMP is increasingly recognised as an important signalling molecule in higher plants, ACs have remained somewhat elusive. Here we used a search motif derived from experimentally tested guanylyl cyclases (GCs), substituted the residues essential for substrate specificity and identified the Arabidopsis thaliana K(+)-uptake permease 7 (AtKUP7) as one of several candidate ACs. Firstly, we show that a recombinant N-terminal, cytosolic domain of AtKUP7(1-100) is able to complement the AC-deficient mutant cyaA in Escherichia coli and thus restoring the fermentation of lactose, and secondly, we demonstrate with both enzyme immunoassays and mass spectrometry that a recombinant AtKUP7(1-100) generates cAMP in vitro.

Comprehensive analysis of chemokine-induced cAMP-inhibitory responses using a real-time luminescent biosensor

Chemokine receptors are members of the G-protein-coupled receptor (GPCR) family coupled to members of the Gi class, whose primary function is to inhibit the cellular adenylate cyclase. We used a cAMP-related and PKA-based luminescent biosensor (GloSensor™ F-22) to monitor the real-time downstream response of chemokine receptors, especially CX3CR1 and CXCR4, after activation with their cognate ligands CX3CL1 and CXCL12. We found that the amplitudes and kinetic profiles of the chemokine responses were conserved in various cell types and were independent of the nature and concentration of the molecules used for cAMP prestimulation, including either the adenylate cyclase activator forskolin or ligands mediating Gs-mediated responses like prostaglandin E2 or beta-adrenergic agonist. We conclude that the cAMP chemokine response is robustly conserved in various inflammatory conditions. Moreover, the cAMP-related luminescent biosensor appears as a valuable tool to analyze the details of Gi-mediated cAMP-inhibitory cellular responses, even in native conditions and could help to decipher their precise role in cell function.

Testosterone regulates levels of cystic fibrosis transmembrane regulator, adenylate cyclase, and cAMP in the seminal vesicles of orchidectomized rats

Secretions of chloride (Cl(-))- and bicarbonate (HCO3(-))-rich fluid by the seminal vesicles could involve cystic fibrosis transmembrane regulator (CFTR), which activity can be stimulated by cAMP generated from the reaction involving adenylate cyclase (AC). In this study, we investigated levels of CFTR, AC, and cAMP in the seminal vesicles under testosterone influence. Orchidectomized adult male rats received 7-day treatment with 125 or 250 μg/kg/day of testosterone with or without flutamide or finasteride. At the end of the treatment, animals were sacrificed and seminal vesicles were harvested for analyses of CFTR and AC protein expression level by Western blotting. Distribution of CFTR and AC in seminal vesicles was observed by immunohistochemistry. Levels of cAMP and dihydrotestosterone in seminal vesicle homogenates were measured by ELISA. Cystic fibrosis transmembrane regulator, AC, and cAMP levels increased with increasing doses of testosterone (P < 0.05 compared to nontreated orchidectomized rats). Cystic fibrosis transmembrane regulator and AC were expressed at the apical membrane of the epithelium lining the seminal vesicle lumen with higher expression levels observed in testosterone-treated rats than in non-treated orchidectomized rats (P < 0.05). The inhibitory effects of flutamide or finasteride on these parameters were greater in 250 μg/kg/day testosterone-treated rats than their effects in 125 μg/kg/day testosterone-treated rats. Higher dihydrotestosterone levels were observed in seminal vesicle homogenates after treatment with 250 μg/kg/day than with 125 μg/kg/day of testosterone (P < 0.05). Increased levels of CFTR, AC, and cAMP in seminal vesicles might contribute toward an increase in Cl(-) and HCO3(-) concentrations in the seminal fluid as reported under testosterone influence.

Calcium signaling and the novel anti-proliferative effect of the UTP-sensitive P2Y11 receptor in rat cardiac myofibroblasts

During myocardial ischemia and reperfusion both purines and pyrimidines are released into the extracellular milieu, thus creating a signaling wave that propagates to neighboring cells via membrane-bound P2 purinoceptors activation. Cardiac fibroblasts (CF) are important players in heart remodeling, electrophysiological changes and hemodynamic alterations following myocardial infarction. Here, we investigated the role UTP on calcium signaling and proliferation of CF cultured from ventricles of adult rats. Co-expression of discoidin domain receptor 2 and α-smooth muscle actin indicate that cultured CF are activated myofibroblasts. Intracellular calcium ([Ca(2+)]i) signals were monitored in cells loaded with Fluo-4 NW. CF proliferation was evaluated by the MTT assay. UTP and the selective P2Y4 agonist, MRS4062, caused a fast desensitizing [Ca(2+)]i rise originated from thapsigargin-sensitive internal stores, which partially declined to a plateau providing the existence of Ca(2+) in the extracellular fluid. The biphasic [Ca(2+)]i response to UTP was attenuated respectively by P2Y4 blockers, like reactive blue-2 and suramin, and by the P2Y11 antagonist, NF340. UTP and the P2Y2 receptor agonist MRS2768 increased, whereas the selective P2Y11 agonist NF546 decreased, CF growth; MRS4062 was ineffective. Blockage of the P2Y11 receptor or its coupling to adenylate cyclase boosted UTP-induced CF proliferation. Confocal microscopy and Western blot analysis confirmed the presence of P2Y2, P2Y4 and P2Y11 receptors. Data indicate that besides P2Y4 and P2Y2 receptors which are responsible for UTP-induced [Ca(2+)]i transients and growth of CF, respectively, synchronous activation of the previously unrecognized P2Y11 receptor may represent an important target for anti-fibrotic intervention in cardiac remodeling.