Nucleotide Signaling Pathways Research Articles

Cyclic nucleotide phosphodiesterases: therapeutic targets incardiac hypertrophy and failure

Cyclic nucleotide phosphodiesterases (PDEs) modulate neurohormonal regulation of cardiac function by degrading cAMP and cGMP. In cardiomyocytes, multiple isoforms of PDEs with different enzymatic properties and subcellular locally regulate cyclic nucleotide levels and associated cellular functions. This organisation is severely disrupted during hypertrophy and heart failure (HF), which may contribute to disease progression. Clinically, PDE inhibition has been seen as a promising approach to compensate for the catecholamine desensitisation that accompanies heart failure. Although PDE3 inhibitors such as milrinone or enoximone can be used clinically to improve systolic function and relieve the symptoms of acute CHF, their chronic use has proved detrimental. Other PDEs, such as PDE1, PDE2, PDE4, PDE5, PDE9 and PDE10, have emerged as potential new targets for the treatment of HF, each with a unique role in local cyclic nucleotide signalling pathways. In this review, we describe cAMP and cGMP signalling in cardiomyocytes and present the different families of PDEs expressed in the heart and their modifications in pathological cardiac hypertrophy and HF. We also review results from preclinical models and clinical data indicating the use of specific PDE inhibitors or activators that may have therapeutic potential in CI.

Identification of blood exosomal metabolomic profiling for high-altitude cerebral edema

High-altitude cerebral edema (HACE) is a severe neurological condition that can occur at high altitudes. It is characterized by the accumulation of fluid in the brain, leading to a range of symptoms, including severe headache, confusion, loss of coordination, and even coma and death. Exosomes play a crucial role in intercellular communication, and their contents have been found to change in various diseases. This study analyzed the metabolomic characteristics of blood exosomes from HACE patients compared to those from healthy controls (HCs) with the aim of identifying specific metabolites or metabolic pathways associated with the development of HACE conditions. A total of 21 HACE patients and 21 healthy controls were recruited for this study. Comprehensive metabolomic profiling of the serum exosome samples was conducted using ultraperformance liquid chromatography–tandem mass spectrometry (UPLC‒MS/MS). Additionally, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was performed to identify the metabolic pathways affected in HACE patients. Twenty-six metabolites, including ( +)-camphoric acid, choline, adenosine, adenosine 5′-monophosphate, deoxyguanosine 5′-monophosphate, guanosine, and hypoxanthine-9-β-D-arabinofuranoside, among others, exhibited significant changes in expression in HACE patients compared to HCs. Additionally, these differentially abundant metabolites were confirmed to be potential biomarkers for HACE. KEGG pathway enrichment analysis revealed several pathways that significantly affect energy metabolism regulation (such as purine metabolism, thermogenesis, and nucleotide metabolism), estrogen-related pathways (the estrogen signaling pathway, GnRH signaling pathway, and GnRH pathway), cyclic nucleotide signaling pathways (the cGMP-PKG signaling pathway and cAMP signaling pathway), and hormone synthesis and secretion pathways (renin secretion, parathyroid hormone synthesis, secretion and action, and aldosterone synthesis and secretion). In patients with HACE, adenosine, guanosine, and hypoxanthine-9-β-D-arabinofuranoside were negatively correlated with height. Deoxyguanosine 5′-monophosphate is negatively correlated with weight and BMI. Additionally, LPE (18:2/0:0) and pregnanetriol were positively correlated with age. This study identified potential biomarkers for HACE and provided valuable insights into the underlying metabolic mechanisms of this disease. These findings may lead to potential targets for early diagnosis and therapeutic intervention in HACE patients.

Deletion of podocyte Rho-associated, coiled-coil-containing protein kinase 2 protects mice from focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) shares podocyte damage as an essential pathological finding. Several mechanisms underlying podocyte injury have been proposed, but many important questions remain. Rho-associated, coiled-coil-containing protein kinase 2 (ROCK2) is a serine/threonine kinase responsible for a wide array of cellular functions. We found that ROCK2 is activated in podocytes of adriamycin (ADR)-induced FSGS mice and cultured podocytes stimulated with ADR. Conditional knockout mice in which the ROCK2 gene was selectively disrupted in podocytes (PR2KO) were resistant to albuminuria, glomerular sclerosis, and podocyte damage induced by ADR injection. In addition, pharmacological intervention for ROCK2 significantly ameliorated podocyte loss and kidney sclerosis in a murine model of FSGS by abrogating profibrotic factors. RNA sequencing of podocytes treated with a ROCK2 inhibitor proved that ROCK2 is a cyclic nucleotide signaling pathway regulator. Our study highlights the potential utility of ROCK2 inhibition as a therapeutic option for FSGS.

Mechanism of Wendan decoction in preventing obesity by regulating multiple signal pathway networks based on gene promoter methylation

ObjectiveTo investigate the potential mechanism of Wendan decoction in obesity by screening target genes with promoter region methylation changes and constructing a multiple signaling pathways network based on promoter methylation. MethodsThe methylation degree of Itgad, Col8a1, Adra2b, Jund, Rab2a, Wnt8b, Fzd9, B4galt7, Pik3cd, Creb1, Stard8, and Mmp1 in the abdominal adipose tissue of obese rats was determined using the Agena MassARRAY system. Western blot was performed to assess protein expression levels. Target genes were identified based on the methylation degree in the promoter region and protein expression. Enrichment analysis of signaling pathways was conducted to identify relevant target genes and obtain a multiple signaling pathway network associated with obesity. Core and terminal effector molecules in the pathway networks were selected as research targets for reverse transcription-polymerase chain reaction (RT-PCR) analysis. ResultsFour genes (Adra2b, Creb1, Itgad, and Pik3cd) showed a degree of promoter methylation consistent with their respective protein expression levels. Among them, Adra2b, Creb1, and Pik3cd expression increased, while that of Itgad decreased. Enrichment analysis revealed that Creb1 and Pik3cd were involved in 6 signaling pathways related to obesity: tumor necrosis factor (TNF) signaling pathway, growth hormone synthesis/secretion and action, adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling pathway, relaxin signaling pathway, cyclic nucleotide (cAMP) signaling pathway, and phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway. Subsequently, a multiple signaling pathways network was constructed based on promoter methylation. Key molecules including protein kinase B (AKT), mechanistic target of rapamycin complex 1 (mTORC1), and unc-51 like autophagy activating kinase 1 (ULK1), as well as terminal effector molecules interleukin-1β (IL-1β), interleukin-6 (IL-6), and chemokine (C-X-C motif) ligand 2 (CXCL2) were selected as research targets. Wendan decoction decreased the expressions of AKT, mTORC1, IL-1β, IL-6, and CXCL2 while up-regulating ULK1 expression. ConclusionThe mechanism of Wendan decoction in preventing obesity involves the regulation of multiple signaling pathways through the control of Creb1 and Pik3cd gene promoter methylation. However, the associated multi-path gene regulation mechanism in preventing obesity is complex. Thus, further exploration is needed to elucidate the role of methylation changes in this mechanism.

Dissecting the molecular dance: c-di-GMP, cAMP-CRP, and VfmH collaboration in pectate lyase regulation for Dickeya dadantii-unveiling the soft rot pathogen's strategy.

Dickeya dadantii is a Gram-negative bacterium that causes soft rot diseases in a variety of plants. This pathogen secretes pectate lyase (Pel) enzymes to degrade the plant cell wall, a process controlled by the bacterial second messenger cyclic diguanylate monophosphate (c-di-GMP). VfmH is a Fis-family response regulator of the Vfm quorum sensing system, which has been previously reported to positively regulate pel transcription. Our results demonstrated that VfmH upregulated the production of Pel at low c-di-GMP levels, which was suppressed by c-di-GMP via deleting gene egcpB, encoding a phosphodiesterase that degrades c-di-GMP. Multiple sequence alignments between FleQ, a known c-di-GMP binding protein, and VfmH revealed several potential c-di-GMP binding motifs. We further validated these motifs via single amino acid substitutions. Indeed, derivatives of VfmH, including VfmHR195A, VfmHR279A, and VfmHR344A, abolished the c-di-GMP binding ability and the corresponding regulation in Pel. We found that VfmH exhibited ATPase activity, and this could be hindered by c-di-GMP binding. Interestingly, our results showed that VfmH interacted with CRP, suggesting that the cyclic AMP (cAMP) signaling pathway is also involved in the VfmH-mediated Pel regulation. Taken together, our study suggested that D. dadantii amalgamates both c-di-GMP and cAMP signaling networks along with the Vfm quorum sensing pathway to control Pel.IMPORTANCEBacteria respond to environmental changes and adapt to host systems. The response regulator VfmH of the Vfm quorum sensing system regulates a crucial virulence factor, pectate lyase (Pel), in Dickeya dadantii. At high c-di-GMP concentrations, VfmH binds c-di-GMP, resulting in the loss of its activation property in the Pel and virulence regulation in D. dadantii. VfmH binds to c-di-GMP via three conserved arginine residues, and mutations of these residues eliminate the c-di-GMP-related phenotypes of VfmH in Pel synthesis. Our data also show that VfmH interacts with CRP to regulate pelD transcription, thus integrating cyclic AMP and c-di-GMP signaling pathways to control virulence in D. dadantii. We propose that VfmH is an important intermediate factor incorporating quorum sensing and nucleotide signaling pathways for the collective regulation of D. dadantii pathogenesis.

Endometrial protein expression and phosphorylation landscape decipher aberrant insulin and mTOR signalling in patients with recurrent pregnancy loss

What are the proteomic and phosphoproteomic differences between the endometrium of women with recurrent pregnancy loss (RPL) and the endometrium of healthy control women during the proliferative and secretory phases of the menstrual cycle? In total, 54 endometrial samples were collected during the proliferative and secretory phases from women with RPL (n = 28) and healthy controls (n = 26). Comprehensive proteomic and phosphoproteomic analyses were conducted using label-free liquid chromatography-tandem mass spectrometry (n = 44), and verified through Western blotting (n = 10). Three comparison groups were established: total RPL endometrium versus total control endometrium; RPL proliferative endometrium versus control proliferative endometrium; and RPL secretory endometrium versus control secretory endometrium. Differentially expressed proteins and differentially phosphorylated proteins were identified in the three comparison groups. Combining pathway enrichment, network analysis and soft clustering analysis, the insulin/cyclic nucleotide signalling pathway and AMPK/mTOR signalling pathway were identified as the major contributors to the aberration of RPL endometrium. Western blotting verified altered expression of four proteins: cAMP-dependent protein kinase type I-β regulatory subunit, adenylate cyclase type 3, 5'-AMP-activated protein kinase catalytic subunit α-2 and phosphatidate phosphatase LPIN2. This exploratory study provides insights into the differentiated protein expression and phosphorylation profiles of the endometrium of women with RPL in both the proliferative and sectretory phases of the menstrual cycle. The results highlight potential proteins associated with the pathogenesis of RPL that may serve as potential indicators for RPL. The findings contribute to the identification of potential targets for RPL treatment as well as its pathogenesis.

Surfaces modified with small molecules that interfere with nucleotide signaling reduce Staphylococcus epidermidis biofilm and increase the efficacy of ciprofloxacin

Staphylococcus epidermidis are common bacteria associated with biofilm related infections on implanted medical devices. Antibiotics are often used in combating such infections, but they may lose their efficacy in the presence of biofilms. Bacterial intracellular nucleotide second messenger signaling plays an important role in biofilm formation, and interference with the nucleotide signaling pathways provides a possible way to control biofilm formation and to increase biofilm susceptibility to antibiotic therapy. This study synthesized small molecule derivates of 4-arylazo-3,5-diamino-1 H-pyrazole (named as SP02 and SP03) and found these molecules inhibited S. epidermidis biofilm formation and induced biofilm dispersal. Analysis of bacterial nucleotide signaling molecules showed that both SP02 and SP03 significantly reduced cyclic dimeric adenosine monophosphate (c-di-AMP) levels in S. epidermidis at doses as low as 25 µM while having significant effects on multiple nucleotides signaling including cyclic dimeric guanosine monophosphate (c-di-GMP), c-di-AMP, and cyclic adenosine monophosphate (cAMP) at high doses (100 µM or greater). We then tethered these small molecules to polyurethane (PU) biomaterial surfaces and investigated biofilm formation on the modified surfaces. Results showed that the modified surfaces significantly inhibited biofilm formation during 24 h and 7-day incubations. The antibiotic ciprofloxacin was used to treat these biofilms and the efficacy of the antibiotic (2 µg/mL) was found to increase from 94.8% on unmodified PU surfaces to > 99.9% on both SP02 and SP03 modified surfaces (>3 log units). Results demonstrated the feasibility of tethering small molecules that interfere with nucleotide signaling onto polymeric biomaterial surfaces and in a way that interrupts biofilm formation and increases antibiotic efficacy for S. epidermidis infections.

Cyclic nucleotide phosphodiesterases as therapeutic targets in cardiac hypertrophy and heart failure.

Cyclic nucleotide phosphodiesterases (PDEs) modulate the neurohormonal regulation of cardiac function by degrading cAMP and cGMP. In cardiomyocytes, multiple PDE isozymes with different enzymatic properties and subcellular localization regulate local pools of cyclic nucleotides and specific functions. This organization is heavily perturbed during cardiac hypertrophy and heart failure (HF), which can contribute to disease progression. Clinically, PDE inhibition has been considered a promising approach to compensate for the catecholamine desensitization that accompanies HF. Although PDE3 inhibitors, such as milrinone or enoximone, have been used clinically to improve systolic function and alleviate the symptoms of acute HF, their chronic use has proved to be detrimental. Other PDEs, such as PDE1, PDE2, PDE4, PDE5, PDE9 and PDE10, have emerged as new potential targets to treat HF, each having a unique role in local cyclic nucleotide signalling pathways. In this Review, we describe cAMP and cGMP signalling in cardiomyocytes and present the various PDE families expressed in the heart as well as their modifications in pathological cardiac hypertrophy and HF. We also appraise the evidence from preclinical models as well as clinical data pointing to the use of inhibitors or activators of specific PDEs that could have therapeutic potential in HF.

In Vitro Antiplatelet Activity of Mulberroside C through the Up-Regulation of Cyclic Nucleotide Signaling Pathways and Down-Regulation of Phosphoproteins.

Physiological agonists trigger signaling cascades, called “inside-out signaling”, and activated platelets facilitate adhesion, shape change, granule release, and structural change of glycoprotein IIb/IIIa (αIIb/β3). Activated αIIb/β3 interacts with fibrinogen and begins second signaling cascades called “outside-in signaling”. These two signaling pathways can lead to hemostasis or thrombosis. Thrombosis can occur in arterial and venous blood vessels and is a major medical problem. Platelet-mediated thrombosis is a major cause of cardiovascular disease (CVD). Therefore, controlling platelet activity is important for platelet-mediated thrombosis and cardiovascular diseases. In this study, focus on Morus Alba Linn, a popular medicinal plant, to inhibit the function of platelets and found the containing component mulberroside C. We examine the effect of mulberroside C on the regulation of phosphoproteins, platelet-activating factors, and binding molecules. Agonist-induced human platelet aggregation is dose-dependently inhibited by mulberroside C without cytotoxicity, and it decreased Ca2+ mobilization and p-selectin expression through the upregulation of inositol 1, 4, 5-triphosphate receptor I (Ser1756), and downregulation of extracellular signal-regulated kinase (ERK). In addition, mulberroside C inhibited thromboxane A2 production, fibrinogen binding, and clot retraction. Our results show antiplatelet effects and antithrombus formation of mulberroside C in human platelets. Thus, we confirm that mulberroside C could be a potential phytochemical for the prevention of thrombosis-mediated CVDs.

Alterations of cAMP/cGMP Signaling Pathways in Lupus Nephritis

Systemic lupus erythematosus (SLE) is an autoimmune disease with a broad spectrum of clinical manifestations, but its pathogenesis remains fairly understood. Cyclic nucleotide signaling pathways in immune cells and kidney are emerging as cellular mechanisms governing SLE disease progression. Upregulations of cGMP/cAMP metabolism lead to lupus nephritis and abnormal kidney remodeling/hypertrophy. PDE4 family remains the major cAMP hydrolyzing enzyme as PDE1 is responsible for cGMP breakdown in kidney. SLE disease progression to lupus nephritis is correlated with increase PDE1 and PDE4 activities resulting in lower cyclic nucleotide levels in kidney. Administration of Nimodipine, a PDE1 inhibitor prevents the lymphoproliferative phenotype and exert anti-proliferative effects on mesangial cells while PDE4 inhibitor NCS 613 prevents inflammatory cytokines release, immune complex deposition, and nephritis in MRL/lpr lupus prone mice. In this review, we highlight recent findings of alterations of cyclic nucleotide signaling pathways in lupus nephritis. Given the role of cAMP/cGMP signaling in kidney function, dual inhibition of PDE1 and PDE4 may represent a promising therapeutic approach to tackle lupus nephritis.

Ulmus parvifolia Modulates Platelet Functions and Inhibits Thrombus Formation by Regulating Integrin αIIbβ3 and cAMP Signaling.

BackgroundThe prevalence of cardiovascular diseases (CVDs) is increasing at a high rate, and the available treatment options, sometimes, have complications which necessitates the need to develop safer and efficacious approaches. Ethnomedicinal applications reportedly reduce CVD risk. Ulmus parvifolia Jacq. (Ulmaceae) commonly known as Chinese Elm or Lacebark Elm, is native to China, Japan, and Korea. It exhibits anti-inflammatory, antiviral, and anticancer properties, but its anti-platelet properties have not yet been elucidated.PurposeTo investigate the pharmacological anti-platelet and anti-thrombotic effects of U. parvifolia bark extract.Study Design and MethodsHuman and rat washed platelets were prepared; light transmission aggregometry and scanning electron microscopy was performed to assess platelet aggregation and the change in platelet shape, respectively. Intracellular calcium mobilization, ATP release, and thromboxane-B2 production were also measured. Integrin αIIbβ3 activation was analyzed in terms of fibrinogen binding, fibronectin adhesion, and clot retraction. The expression of MAPK, Src, and PI3K/Akt pathway proteins was examined. Cyclic nucleotide signaling pathway was evaluated via cAMP elevation and VASP phosphorylation. Anti-thrombotic activity of the extract was evaluated in vivo using an arteriovenous shunt rat model, whereas its effect on hemostasis in mice was assessed via bleeding time assay.Results U. parvifolia extract significantly inhibited human and rat platelet aggregation in a dose-dependent manner along with inhibition of calcium mobilization, dense granule secretion, and TxB2 production. Integrin αIIbβ3 mediated inside-out and outside-in signaling events, as evidenced by the inhibition of fibrinogen binding, fibronectin adhesion, and clot retraction. The extract significantly reduced phosphorylation of Src, MAPK (ERK, JNK, and p38MAPK), and PI3K/Akt pathway proteins. Cyclic-AMP levels were elevated in U. parvifolia-treated platelets, while PKAαβγ and VASPser157 phosphorylation was enhanced. U. parvifolia reduced thrombus weight in rats and moderately increased bleeding time in mice.Conclusion U. parvifolia modulates platelet responses and inhibit thrombus formation by regulating integrin αIIbβ3 mediated inside-out and outside-in signaling events and cAMP signaling pathway.

Cyclic Nucleotide Signaling Pathways in Apicomplexan Parasites Provide a Valuable Source for Novel Drug Targets

Cyclic Nucleotide Signaling Pathways in Apicomplexan Parasites Provide a Valuable Source for Novel Drug Targets

Abstract C069: The identification of MRTX849, a novel KRASG12C inhibitor under clinical investigation, provides insight toward therapeutic susceptibility of KRAS mutant cancers

Abstract The ability to effectively target mutated KRAS has remained elusive despite decades of research. MRTX849 was identified via structure-based drug design as a potent, selective, and covalent KRASG12C inhibitor that exhibits favorable drug-like properties. MRTX849 is presently under evaluation in clinical trials and its discovery and evaluation is disclosed here for the first time. MRTX849 demonstrated selective modification of the mutant cysteine residue at amino acid residue 12 in GDP-bound KRASG12C and inhibited KRAS-dependent signaling in vitro and in vivo. In multiple KRASG12C positive cell lines in vitro, MRTX849 treatment demonstrated covalent modification of mutant KRAS and/or inhibition of active KRAS at concentrations as low as 2 nM with near maximal inhibition observed at 15 nM. In vivo, clear evidence of dose-dependent modification of KRASG12C and inhibition of KRAS-dependent signal transduction was observed in multiple KRASG12C mutant tumor models. MRTX849 demonstrated marked tumor regression in 17 out of 26 (65%) of KRASG12C-positive cell line- and patient-derived xenograft (PDX) models but not in tumor models without KRASG12C mutations. While MRTX849 commonly elicited tumor regression, a subset of models was less sensitive to treatment or exhibited tumor stasis after an initial response phase. Comprehensive pharmacodynamic and pharmacogenomic profiling in these models identified mechanisms implicated in limiting anti-tumor response in refractory models including extrinsic factors impacting KRAS nucleotide cycling and/or signaling pathways that induce feedback reactivation and/or bypass KRAS dependence. These factors included upstream activation of ERBB family receptor tyrosine kinases (RTKs) as well as genetic dysregulation of cell cycle transition genes. Based on these observations, combination strategies designed to co-target signaling feedback and bypass pathways were evaluated in multiple tumor models. Afatinib and the SHP2 inhibitor, RMC-4550, in combination with MRTX849 validated these therapeutic hypotheses and the combinations demonstrated marked tumor regression in several tumor models, including models that were refractory to either single agent. MRTX849 in combination with the CDK4/6 inhibitor palbociclib also demonstrated a marked antitumor response; notably in tumor models harboring CDKN2A deletion or other genetic alterations implicated in cell cycle dysregulation. Together, these data indicate the therapeutic susceptibility and broad dependence of KRAS G12C mutation-positive tumors on KRAS for tumor cell growth and survival and provide insight toward the molecular basis of response to single agent and combinatorial therapies. Citation Format: James G Christensen, Jay B Fell, Jill Hallin, Brian Baer, Lars engstrom, James Blake, David Briere, Josh Ballard, Michael Burkhard, John Fischer, Guy Vigers, Ruth Aranda, Vickie Bowcut, Andrew Calinisan, Lauren Hargis, Niranjan Sudhakar, Matt Marx, Peter Olson. The identification of MRTX849, a novel KRASG12C inhibitor under clinical investigation, provides insight toward therapeutic susceptibility of KRAS mutant cancers [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C069. doi:10.1158/1535-7163.TARG-19-C069

Nucleotide signaling pathway convergence in a cAMP-sensing bacterial c-di-GMP phosphodiesterase.

Bacterial usage of the cyclic dinucleotide c‐di‐GMP is widespread, governing the transition between motile/sessile and unicellular/multicellular behaviors. There is limited information on c‐di‐GMP metabolism, particularly on regulatory mechanisms governing control of EAL c‐di‐GMP phosphodiesterases. Herein, we provide high‐resolution structures for an EAL enzyme Bd1971, from the predatory bacterium Bdellovibrio bacteriovorus, which is controlled by a second signaling nucleotide, cAMP. The full‐length cAMP‐bound form reveals the sensory N‐terminus to be a domain‐swapped variant of the cNMP/CRP family, which in the cAMP‐activated state holds the C‐terminal EAL enzyme in a phosphodiesterase‐active conformation. Using a truncation mutant, we trap both a half‐occupied and inactive apo‐form of the protein, demonstrating a series of conformational changes that alter juxtaposition of the sensory domains. We show that Bd1971 interacts with several GGDEF proteins (c‐di‐GMP producers), but mutants of Bd1971 do not share the discrete phenotypes of GGDEF mutants, instead having an elevated level of c‐di‐GMP, suggesting that the role of Bd1971 is to moderate these levels, allowing “action potentials” to be generated by each GGDEF protein to effect their specific functions.

Hijacking the Bacterial Circuitry of Biofilm Processes via Chemical "Hot-Wiring": An Under-explored Avenue for Therapeutic Development.

Biofilm-associated infections are linked to chronic and recurring illnesses. These infections are often not susceptible to current antibiotic treatments because of the protective exocellular matrix and subpopulations of dormant or "persister" cells. Targeting bacterial circuitry involved in biofilm formation, including two-component systems, quorum sensing, polysaccharide structural integrity, and cyclic nucleotide signaling pathways, has the potential to expand the existing arsenal of therapeutics, thus catalyzing a second golden age of antibiotic development.

Genetic Association of Phosphodiesterases With Human Cognitive Performance.

Recent, large-scale, genome-wide association studies (GWAS) provide a first view of the genetic fine structure of cognitive performance in healthy individuals. These studies have pooled data from up to 1.1 million subjects based on simple measures of cognitive performance including educational attainment, self-reported math ability, highest math class taken, and pooled, normalized scores from cognitive tests. These studies now allow the genome-wide interrogation of genes and pathways for their potential impact on human cognitive performance. The phosphodiesterase (PDE) enzymes regulate key cyclic nucleotide signaling pathways. Many are expressed in the brain and have been the targets of CNS drug discovery. Genetic variation in PDE1C, PDE4B and PDE4D associates with multiple measures of human cognitive function. The large size of the human PDE4B and PDE4D genes allows genetic fine structure mapping to transcripts encoding dimeric (long) forms of the enzymes. Upstream and downstream effectors of the cAMP pathway modulated by PDE4D [adenylate cyclase 1 (ADCY1), ADCY8, PRKAR1A, CREB1, or CREBBP] did not show genetic association with cognitive performance, however, genetic association was seen with brain derived neurotrophic factor (BDNF), a gene whose expression is modulated by cAMP. Notably absent was genetic association in healthy subjects to targets of CNS drug discovery designed to improve cognition in disease states by the modulation of cholinergic [acetylcholinesterase (ACHE), choline acetyltransferase (CHAT), nicotinic alpha 7 acetylcholine receptor (CHRNA7)], serotonergic (HTR6), histaminergic (HRH3), or glutamatergic (GRM5) pathways. These new data provide a rationale for exploring the therapeutic benefit of selective inhibitors of PDE1C, PDE4B and PDE4D in CNS disorders affecting cognition.

RNA Sequencing Reveals Differential Gene Expression of Cerrena Unicolor in Response to Variable Lighting Conditions.

To elucidate the light-dependent gene expression in Cerrena unicolor FCL139, the transcriptomes of the fungus growing in white, blue, green, and red lighting conditions and darkness were analysed. Among 10,413 all-unigenes detected in C. unicolor, 7762 were found to be expressed in all tested conditions. Transcripts encoding putative fungal photoreceptors in the C. unicolor transcriptome were identified. The number of transcripts uniquely produced by fungus ranged from 20 during its growth in darkness to 112 in the green lighting conditions. We identified numerous genes whose expression differed substantially between the darkness (control) and each of the light variants tested, with the greatest number of differentially expressed genes (DEGs) (454 up- and 457 down-regulated) observed for the white lighting conditions. The DEGs comprised those involved in primary carbohydrate metabolism, amino acid metabolism, autophagy, nucleotide repair systems, signalling pathways, and carotenoid metabolism as defined using Kyoto Encyclopedia of Genes and Genomes (KEGG) database. The analysis of the expression profile of genes coding for lignocellulose-degrading enzymes suggests that the wood-degradation properties of C. unicolor may be independent of the lighting conditions and may result from the overall stimulation of fungal metabolism by daylight.

Druggable Targets in Cyclic Nucleotide Signaling Pathways in Apicomplexan Parasites and Kinetoplastids against Disabling Protozoan Diseases in Humans.

Cell signaling in eukaryotes is an evolutionarily conserved mechanism to respond and adapt to various environmental changes. In general, signal sensation is mediated by a receptor which transfers the signal to a cascade of effector proteins. The cyclic nucleotides 3′,5′-cyclic adenosine monophosphate (cAMP) and 3′,5′-cyclic guanosine monophosphate (cGMP) are intracellular messengers mediating an extracellular stimulus to cyclic nucleotide-dependent kinases driving a change in cell function. In apicomplexan parasites and kinetoplastids, which are responsible for a variety of neglected, tropical diseases, unique mechanisms of cyclic nucleotide signaling are currently identified. Collectively, cyclic nucleotides seem to be essential for parasitic proliferation and differentiation. However, there is no a genomic evidence for canonical G-proteins in these parasites while small GTPases and secondary effector proteins with structural differences to host orthologues occur. Database entries encoding G-protein-coupled receptors (GPCRs) are still without functional proof. Instead, signals from the parasite trigger GPCR-mediated signaling in the host during parasite invasion and egress. The role of cyclic nucleotide signaling in the absence of G-proteins and GPCRs, with a particular focus on small GTPases in pathogenesis, is reviewed here. Due to the absence of G-proteins, apicomplexan parasites and kinetoplastids may use small GTPases or their secondary effector proteins and host canonical G-proteins during infection. Thus, the feasibility of targeting cyclic nucleotide signaling pathways in these parasites, will be an enormous challenge for the identification of selective, pharmacological inhibitors since canonical host proteins also contribute to pathogenesis.

Exploring the Links between Nucleotide Signaling and Quorum Sensing Pathways in Regulating Bacterial Virulence.

The survival of all organisms depends on implementation of appropriate phenotypic responses upon perception of relevant environmental stimuli. Sensory inputs are propagated via interconnected biochemical and/or electrical cascades mediated by diverse signaling molecules, including gases, metal cations, lipids, peptides, and nucleotides. These networks often comprise second messenger signaling systems in which a ligand (the primary messenger) binds to an extracellular receptor, thereby altering the intracellular concentration of a second messenger molecule which ultimately modulates gene expression through interaction with various effectors. The identification of intersections of these signaling pathways, such as nucleotide second messengers and quorum sensing, provides new insights into the mechanisms by which bacteria use multiple inputs to regulate cellular metabolism and phenotypes. Further investigations of the overlap between bacterial signaling pathways may yield new targets and methods to control bacterial behavior, such as biofilm formation and virulence.

Cyclic nucleotide signaling in Mycobacterium tuberculosis: an expanding repertoire.

Mycobacterium tuberculosis (Mtb) is one of the most successful microbial pathogens, and currently infects over a quarter of the world's population. Mtb's success depends on the ability of the bacterium to sense and respond to dynamic and hostile environments within the host, including the ability to regulate bacterial metabolism and interactions with the host immune system. One of the ways Mtb senses and responds to conditions it faces during infection is through the concerted action of multiple cyclic nucleotide signaling pathways. This review will describe how Mtb uses cyclic AMP, cyclic di-AMP and cyclic di-GMP to regulate important physiological processes, and how these signaling pathways can be exploited for the development of novel thereapeutics and vaccines.