Protein Kinase A Regulates Platelet Phosphodiesterase 3A through an A-Kinase Anchoring Protein Dependent Manner.

Platelet activation is critical for haemostasis, but if unregulated can lead to pathological thrombosis. Endogenous platelet inhibitory mechanisms are mediated by prostacyclin (PGI2)-stimulated cAMP signalling, which is regulated by phosphodiesterase 3A (PDE3A). However, spatiotemporal regulation of PDE3A activity in platelets is unknown. Here, we report that platelets possess multiple PDE3A isoforms with seemingly identical molecular weights (100 kDa). One isoform contained a unique N-terminal sequence that corresponded to PDE3A1 in nucleated cells but with negligible contribution to overall PDE3A activity. The predominant cytosolic PDE3A isoform did not possess the unique N-terminal sequence and accounted for >99% of basal PDE3A activity. PGI2 treatment induced a dose and time-dependent increase in PDE3A phosphorylation which was PKA-dependent and associated with an increase in phosphodiesterase enzymatic activity. The effects of PGI2 on PDE3A were modulated by A-kinase anchoring protein (AKAP) disruptor peptides, suggesting an AKAP-mediated PDE3A signalosome. We identified AKAP7, AKAP9, AKAP12, AKAP13, and moesin expressed in platelets but focussed on AKAP7 as a potential PDE3A binding partner. Using a combination of immunoprecipitation, proximity ligation techniques, and activity assays, we identified a novel PDE3A/PKA RII/AKAP7 signalosome in platelets that integrates propagation and termination of cAMP signalling through coupling of PKA and PDE3A.

A PDE3A-SLFN12 Molecular Glue Exhibits Significant Antitumor Activity in TKI-Resistant Gastrointestinal Stromal Tumors.

PURPOSE: Gastrointestinal stromal tumor (GIST), the most common mesenchymal tumor with KIT or PDGFRA driver mutations, is typically treated with tyrosine kinase inhibitors (TKI). However, resistance to TKIs due to secondary mutations is a common challenge in advanced GISTs. In addition, there are currently no effective therapies for several other molecular subtypes, such as succinate dehydrogenase-deficient GISTs. Therefore, novel therapeutic strategies are needed. EXPERIMENTAL DESIGN: To address this need, we tested the efficacy of a novel non-TKI compound, OPB-171775, using patient-derived xenograft models of GISTs. In parallel, we sought to elucidate the mechanism of action of the compound. RESULTS: Our study revealed that OPB-171775 exhibited significant efficacy against GISTs regardless of their KIT mutation status by inducing complex formation between phosphodiesterase 3A (PDE3A) and Schlafen family member 12 (SLFN12), which are highly expressed in GISTs, leading to SLFN12 RNase-mediated cell death. Furthermore, we identified the activation of general control non-derepressible 2 and its downstream response as an effector pathway of SLFN12 in mediating anticancer activity and revealed potential pharmacodynamic markers. CONCLUSIONS: These findings suggest that OPB-171775, with its significant efficacy, could potentially serve as a novel and effective treatment option for advanced GISTs, particularly those resistant to TKIs.

Administration of Liposomal-Based Pde3b Gene Therapy Protects Mice Against Collagen-Induced Rheumatoid Arthritis via Modulating Macrophage Polarization.

Background: Rheumatoid arthritis (RA) is a chronic and systemic autoimmune disease characterized by synovial inflammation and joint destruction. Despite progress in RA therapy, it remains difficult to achieve long-term remission in RA patients. Phosphodiesterase 3B (Pde3b) is a member of the phosphohydrolyase family that are involved in many signal transduction pathways. However, its role in RA is yet to be fully addressed. Methods: Studies were conducted in arthritic DBA/1 mice, a suitable mouse strain for collagen-induced rheumatoid arthritis (CIA), to dissect the role of Pde3b in RA pathogenesis. Next, RNAi-based therapy with Pde3b siRNA-loaded liposomes was assessed in a CIA model. To study the mechanism involved, we investigated the effect of Pde3b knockdown on macrophage polarization and related signaling pathway. Results: We demonstrated that mice with CIA exhibited upregulated Pde3b expression in macrophages. Notably, intravenous administration of liposomes loaded with Pde3b siRNA promoted the macrophage anti-inflammatory program and alleviated CIA in mice, as indicated by the reduced inflammatory response, synoviocyte infiltration, and bone and cartilage erosion. Mechanistic study revealed that depletion of Pde3b increased cAMP levels, by which it enhanced PKA-CREB-C/EBPß pathway to transcribe the expression of anti-inflammatory program-related genes. Conclusion: Our results support that Pde3b is involved in the pathogenesis of RA, and Pde3b siRNA-loaded liposomes might serve as a promising therapeutic approach against RA.

PDE3B regulates KRT6B and increases the sensitivity of bladder cancer cells to copper ionophores.

Cuproptosis is a new Cu-dependent programmed cell death manner that has shown regulatory functions in many tumor types, however, its mechanism in bladder cancer remains unclear. Here, we reveal that Phosphodiesterase 3B (PDE3B), a cuproptosis-associated gene, could reduce the invasion and migration of bladder cancer. PDE3B is downregulated in bladder cancer tissues, which is correlated with better prognosis. Conversely, overexpression of PDE3B in bladder cancer cell could significantly resist invasion and migration, which is consistent with the TCGA database results. Future study demonstrate the anti-cancer effect of PDE3B is mediated by Keratin 6B (KRT6B) which leads to the keratinization. Therefore, PDE3B can reduce KRT6B expression and inhibit the invasion and migration of bladder cancer. Meanwhile, increased expression of PDE3B was able to enhance the sensitivity of Cuproptosis drug thiram. This study show that PDE3B/KRT6B is a potential cancer therapeutic target and PDE3B activation is able to increase the sensitivity of bladder cancer cells to copper ionophores.

ALDOA coordinates PDE3A through the ß-catenin/ID3 axis to stimulate cancer metastasis and M2 polarization in lung cancer with EGFR mutations.

Lung cancer has a high incidence rate and requires more effective treatment strategies and drug options for clinical patients. EGFR is a common genetic alteration event in lung cancer that affects patient survival and drug strategy. Our study discovered aberrant aldolase A (ALDOA) expression and dysfunction in lung cancer patients with EGFR mutations. In addition to investigating relevant metabolic processes like glucose uptake, lactate production, and ATPase activity, we examined multi-omics profiles (transcriptomics, proteomics, and pull-down assays). It was observed that phosphodiesterase 3A (PDE3A) enzyme and ALDOA exhibit correlation, and furthermore, they impact M2 macrophage polarization through ß-catenin and downstream ID3. In addition to demonstrating the aforementioned mechanism of action, our experiments discovered that the PDE3 inhibitor trequinsin has a substantial impact on lung cancer cell lines with EGFR mutants. The trequinsin medication was found to decrease the M2 macrophage polarization status and several cancer phenotypes, in addition to transduction. These findings have potential prognostic and therapeutic applications for clinical patients with EGFR mutation and lung cancer.

Mutations in Phosphodiesterase 3A (PDE3A) Cause Hypertension Without Cardiac Damage.

Hypertension with brachydactyly (HTNB) represents an autosomal dominant form of hypertension. It is a rare syndrome, in which the blood pressure can rise by more than 50 mmHg. If untreated, the patients die of stroke by the age of 50 years. In HTNB, vascular smooth muscle cell proliferation is increased, vasodilation compromised, and the kidney not affected. Surprisingly, after decades of hypertension, HTNB is not associated with hypertension-induced cardiac damage. HTNB is caused by gain-of-function mutations in the PDE3A (phosphodiesterase 3A) gene. The mutant enzymes are hyperactive. PDE3A (phosphodiesterase 3A) hydrolyzes and thereby terminates cyclic adenosine monophosphate signaling in defined cellular compartments. The cardioprotective effect involves local changes of cyclic adenosine monophosphate signaling and inhibition of Ca2+ reuptake into the sarcoplasmic reticulum of cardiac myocytes. This review introduces HTNB and discusses how insight into the molecular mechanisms underlying HTNB could contribute to a better understanding of blood pressure control and lead to PDE3A-directed strategies for the treatment of essential hypertension and the prevention of hypertension-induced cardiac damage. A focus will be on cAMP (cyclic adenosine monophosphate) signaling compartments.

Disruption of Phosphodiesterase 3A Binding to SERCA2 Increases SERCA2 Activity and Reduces Mortality in Mice With Chronic Heart Failure.

BACKGROUND: Increasing SERCA2 (sarco[endo]-plasmic reticulum Ca2+ ATPase 2) activity is suggested to be beneficial in chronic heart failure, but no selective SERCA2-activating drugs are available. PDE3A (phosphodiesterase 3A) is proposed to be present in the SERCA2 interactome and limit SERCA2 activity. Disruption of PDE3A from SERCA2 might thus be a strategy to develop SERCA2 activators. METHODS: Confocal microscopy, 2-color direct stochastic optical reconstruction microscopy, proximity ligation assays, immunoprecipitations, peptide arrays, and surface plasmon resonance were used to investigate colocalization between SERCA2 and PDE3A in cardiomyocytes, map the SERCA2/PDE3A interaction sites, and optimize disruptor peptides that release PDE3A from SERCA2. Functional experiments assessing the effect of PDE3A-binding to SERCA2 were performed in cardiomyocytes and HEK293 vesicles. The effect of SERCA2/PDE3A disruption by the disruptor peptide OptF (optimized peptide F) on cardiac mortality and function was evaluated during 20 weeks in 2 consecutive randomized, blinded, and controlled preclinical trials in a total of 148 mice injected with recombinant adeno-associated virus 9 (rAAV9)-OptF, rAAV9-control (Ctrl), or PBS, before undergoing aortic banding (AB) or sham surgery and subsequent phenotyping with serial echocardiography, cardiac magnetic resonance imaging, histology, and functional and molecular assays. RESULTS: PDE3A colocalized with SERCA2 in human nonfailing, human failing, and rodent myocardium. Amino acids 277-402 of PDE3A bound directly to amino acids 169-216 within the actuator domain of SERCA2. Disruption of PDE3A from SERCA2 increased SERCA2 activity in normal and failing cardiomyocytes. SERCA2/PDE3A disruptor peptides increased SERCA2 activity also in the presence of protein kinase A inhibitors and in phospholamban-deficient mice, and had no effect in mice with cardiomyocyte-specific inactivation of SERCA2. Cotransfection of PDE3A reduced SERCA2 activity in HEK293 vesicles. Treatment with rAAV9-OptF reduced cardiac mortality compared with rAAV9-Ctrl (hazard ratio, 0.26 [95% CI, 0.11 to 0.63]) and PBS (hazard ratio, 0.28 [95% CI, 0.09 to 0.90]) 20 weeks after AB. Mice injected with rAAV9-OptF had improved contractility and no difference in cardiac remodeling compared with rAAV9-Ctrl after aortic banding. CONCLUSIONS: Our results suggest that PDE3A regulates SERCA2 activity through direct binding, independently of the catalytic activity of PDE3A. Targeting the SERCA2/PDE3A interaction prevented cardiac mortality after AB, most likely by improving cardiac contractility.

Mutant Phosphodiesterase 3A Protects From Hypertension-Induced Cardiac Damage.

BACKGROUND: Phosphodiesterase 3A (PDE3A) gain-of-function mutations cause hypertension with brachydactyly (HTNB) and lead to stroke. Increased peripheral vascular resistance, rather than salt retention, is responsible. It is surprising that the few patients with HTNB examined so far did not develop cardiac hypertrophy or heart failure. We hypothesized that, in the heart, PDE3A mutations could be protective. METHODS: We studied new patients. CRISPR-Cas9-engineered rat HTNB models were phenotyped by telemetric blood pressure measurements, echocardiography, microcomputed tomography, RNA-sequencing, and single nuclei RNA-sequencing. Human induced pluripotent stem cells carrying PDE3A mutations were established, differentiated to cardiomyocytes, and analyzed by Ca2+ imaging. We used Förster resonance energy transfer and biochemical assays. RESULTS: We identified a new PDE3A mutation in a family with HTNB. It maps to exon 13 encoding the enzyme's catalytic domain. All hitherto identified HTNB PDE3A mutations cluster in exon 4 encoding a region N-terminally from the catalytic domain of the enzyme. The mutations were recapitulated in rat models. Both exon 4 and 13 mutations led to aberrant phosphorylation, hyperactivity, and increased PDE3A enzyme self-assembly. The left ventricles of our patients with HTNB and the rat models were normal despite preexisting hypertension. A catecholamine challenge elicited cardiac hypertrophy in HTNB rats only to the level of wild-type rats and improved the contractility of the mutant hearts, compared with wild-type rats. The ß-adrenergic system, phosphodiesterase activity, and cAMP levels in the mutant hearts resembled wild-type hearts, whereas phospholamban phosphorylation was decreased in the mutants. In our induced pluripotent stem cell cardiomyocyte models, the PDE3A mutations caused adaptive changes of Ca2+ cycling. RNA-sequencing and single nuclei RNA-sequencing identified differences in mRNA expression between wild-type and mutants, affecting, among others, metabolism and protein folding. CONCLUSIONS: Although in vascular smooth muscle, PDE3A mutations cause hypertension, they confer protection against hypertension-induced cardiac damage in hearts. Nonselective PDE3A inhibition is a final, short-term option in heart failure treatment to increase cardiac cAMP and improve contractility. Our data argue that mimicking the effect of PDE3A mutations in the heart rather than nonselective PDE3 inhibition is cardioprotective in the long term. Our findings could facilitate the search for new treatments to prevent hypertension-induced cardiac damage.

Mechanistic insights on cytotoxicity of KOLR, Cinnamomum pauciflorum Nees leaf derived active ingredient, by targeting signaling complexes of phosphodiesterase 3B and rap guanine nucleotide exchange factor 3.

Protein signaling complexes play important roles in prevention of several cancer types and can be used for development of targeted therapy. The roles of signaling complexes of phosphodiesterase 3B (PDE3B) and Rap guanine nucleotide exchange factor 3 (RAPGEF3), which are two important enzymes of cyclic adenosine monophosphate (cAMP) metabolism, in cancer have not been fully explored. In the current study, a natural product Kaempferol-3-O-(3'',4''-di-E-p-coumaroyl)-α-L-rhamnopyranoside designated as KOLR was extracted from Cinnamomum pauciflorum Nees leaves. KOLR exhibited higher cytotoxic effects against BxCP-3 pancreatic cancer cell line. In BxPC-3 cells, the KOLR could enhance the formation of RAPGEF 3/ PDE3B protein complex to inhibit the activation of Rap-1 and PI3K-AKT pathway, thereby promoting cell apoptosis and inhibiting cell metastasis. Mutation of RAPGEF3 G557A or low expression of PDE3B inactivated the binding action of KOLR resulting in KOLR resistance. The findings of this study show that PDE3B/RAPGEF3 complex is a potential therapeutic cancer target.

PDE4DIP in health and diseases.

Cyclic-AMP (cAMP), the first second messenger to be identified, is synthesized, and is universally utilized as a second messenger, and plays important roles in integrity, and function of organs, including heart. Through its coupling with other intracellular messengers, cAMP facilitates excitation-contraction coupling, increases heart rate and conduction velocity. It is degraded by a class of enzymes called cAMP-dependent phosphodiesterase (PDE), with PDE3 and PDE4 being the predominant isoforms in the heart. This highly diverse class of enzymes degrade cAMP and through anchoring proteins generates dynamic microdomains to target specific proteins and control specific cell functions in response to various stimuli. The impaired function of the anchoring protein either by inherited genetic mutations or acquired injuries results in altered intracellular targeting, and blunted responsiveness to stimulating pathways and contributes to pathological cardiac remodeling, cardiac arrhythmias and reduced cell survival. Recent genetic studies provide compelling evidence for an association between the variants in the anchoring protein PDE4DIP and atrial fibrillation, stroke, and heart failure.

Multiple PDE3A modulators act as molecular glues promoting PDE3A-SLFN12 interaction and induce SLFN12 dephosphorylation and cell death.

The canonical function of phosphodiesterase 3A (PDE3A) is to hydrolyze the phosphodiester bonds in second messenger molecules, such as cyclic AMP (cAMP) and cyclic guanosine monophosphate (cGMP). Recently, a phosphodiesterase-activity-independent role for PDE3A was reported. In this noncanonical function, PDE3A physically interacts with Schlafen 12 (SLFN12) upon treatment of cells with cytotoxic PDE3A modulators. Here, we confirmed that the cytotoxic PDE3A modulators act as molecular glues to initiate the association of PDE3A and SLFN12. The PDE3A-SLFN12 interaction increases the protein stability of SLFN12 located in the cytoplasm, while at the same time also inducing SLFN12 dephosphorylation (including serines 368 and 573). Mutational analysis demonstrates that dephosphorylation is required for cell death induced by cytotoxic PDE3A modulators. Finally, we found that dephosphorylation promoted the rRNA RNase activity of SLFN12 and show that this nucleolytic activity is essential for SLFN12's cell-death-inducing function. Thus, our study deepens the understanding of the biochemical mechanisms underlying SLFN12-mediated cell death.

Diosgenin reduces phosphodiesterase 3B (PDE3B) through AMP-activated protein kinase/ mechanistic target of rapamycin (AMPK/mTOR) signaling pathway to ameliorate streptozotocin-induced pancreatic ß-cell apoptosis and dysfunction.

Diabetes mellitus is a metabolic disease caused by defective insulin secretion and/or insulin action. And insulin is the main hormone released by the pancreatic ß-cells. Diosgenin (DG) is a phytochemical with pharmacological activity that increases insulin secretion in streptozotocin (STZ)-induced pancreatic ß-cells of diabetic rats. In this paper, we investigated the effect and mechanism of DG on cell apoptosis and dysfunction in STZ-induced pancreatic ß-cells. Cell viability was detected by CCK-8, apoptosis by flow cytometry, and apoptosis-related protein expression by Western blot. Western blot and RT-qPCR were performed to detect the expression of related genes. The results showed that in STZ-induced INS-1 cells, DG could improve cell viability, inhibit apoptosis, attenuate oxidative stress levels and increase insulin secretion. Notably, PDE3B was highly expressed in STZ-induced INS-1 cells, while DG could significantly inhibit PDE3B expression in a dose-dependent manner. More importantly, overexpression PDE3B remarkably reversed the effect of DG on STZ-induced INS-1 cells. It is thus clear that DG might inhibit STZ-treated pancreatic ß-cell apoptosis and reduce dysfunction via downregulating PDE3B, which provided a more reliable theoretical basis for the treatment of diabetes mellitus with DG.

Rare and low-frequency exonic variants and gene-by-smoking interactions in pulmonary function.

Genome-wide association studies have identified numerous common genetic variants associated with spirometric measures of pulmonary function, including forced expiratory volume in one second (FEV1), forced vital capacity, and their ratio. However, variants with lower minor allele frequencies are less explored. We conducted a large-scale gene-smoking interaction meta-analysis on exonic rare and low-frequency variants involving 44,429 individuals of European ancestry in the discovery stage and sought replication in the UK BiLEVE study with 45,133 European ancestry samples and UK Biobank study with 59,478 samples. We leveraged data on cigarette smoking, the major environmental risk factor for reduced lung function, by testing gene-by-smoking interaction effects only and simultaneously testing the genetic main effects and interaction effects. The most statistically significant signal that replicated was a previously reported low-frequency signal in GPR126, distinct from common variant associations in this gene. Although only nominal replication was obtained for a top rare variant signal rs142935352 in one of the two studies, interaction and joint tests for current smoking and PDE3B were significantly associated with FEV1. This study investigates the utility of assessing gene-by-smoking interactions and underscores their effects on potential pulmonary function.

Inhibition of Phosphodiesterase 3A by Cilostazol Dampens Proinflammatory Platelet Functions.

OBJECTIVE: platelets possess not only haemostatic but also inflammatory properties, which combined are thought to play a detrimental role in thromboinflammatory diseases such as acute coronary syndromes and stroke. Phosphodiesterase (PDE) 3 and -5 inhibitors have demonstrated efficacy in secondary prevention of arterial thrombosis, partially mediated by their antiplatelet action. Yet it is unclear whether such inhibitors also affect platelets' inflammatory functions. Here, we aimed to examine the effect of the PDE3A inhibitor cilostazol and the PDE5 inhibitor tadalafil on platelet function in various aspects of thromboinflammation. Approach and results: cilostazol, but not tadalafil, delayed ex vivo platelet-dependent fibrin formation under whole blood flow over type I collagen at 1000 s-1. Similar results were obtained with blood from Pde3a deficient mice, indicating that cilostazol effects are mediated via PDE3A. Interestingly, cilostazol specifically reduced the release of phosphatidylserine-positive extracellular vesicles (EVs) from human platelets while not affecting total EV release. Both cilostazol and tadalafil reduced the interaction of human platelets with inflamed endothelium under arterial flow and the release of the chemokines CCL5 and CXCL4 from platelets. Moreover, cilostazol, but not tadalafil, reduced monocyte recruitment and platelet-monocyte interaction in vitro. CONCLUSIONS: this study demonstrated yet unrecognised roles for platelet PDE3A and platelet PDE5 in platelet procoagulant and proinflammatory responses.

Structure of PDE3A-SLFN12 complex reveals requirements for activation of SLFN12 RNase.

DNMDP and related compounds, or velcrins, induce complex formation between the phosphodiesterase PDE3A and the SLFN12 protein, leading to a cytotoxic response in cancer cells that express elevated levels of both proteins. The mechanisms by which velcrins induce complex formation, and how the PDE3A-SLFN12 complex causes cancer cell death, are not fully understood. Here, we show that PDE3A and SLFN12 form a heterotetramer stabilized by binding of DNMDP. Interactions between the C-terminal alpha helix of SLFN12 and residues near the active site of PDE3A are required for complex formation, and are further stabilized by interactions between SLFN12 and DNMDP. Moreover, we demonstrate that SLFN12 is an RNase, that PDE3A binding increases SLFN12 RNase activity, and that SLFN12 RNase activity is required for DNMDP response. This new mechanistic understanding will facilitate development of velcrin compounds into new cancer therapies.

CircSCAP Aggravates Oxidized Low-density Lipoprotein-induced Macrophage Injury by Upregulating PDE3B by miR-221-5p in Atherosclerosis.

ABSTRACT: Atherosclerosis (AS) is a major risk factor for cardiovascular disease, in which circular RNAs play important regulatory roles. This research aimed to explore the biological role of circular RNA Sterol Regulatory Element Binding Transcription Factor Chaperone (circSCAP) (hsa_circ_0001292) in AS development. Real-time PCR or Western blot assay was conducted to analyze RNA or protein expression. Cell proliferation and apoptosis were analyzed by CCK-8 assay and flow cytometry. The levels of lipid accumulation-associated indicators and oxidative stress factors were detected using commercial kits. The levels of inflammatory cytokines were examined using enzyme-linked immunosorbent assay. Intermolecular interaction was verified by dual-luciferase reporter analysis or RNA pull-down analysis. CircSCAP and phosphodiesterase 3B (PDE3B) levels were elevated, whereas the miR-221-5p level was decreased in patients with AS and oxidized low-density lipoprotein (ox-LDL)-induced THP-1 cells. CircSCAP absence suppressed lipid deposition, inflammation, and oxidative stress in ox-LDL-induced THP-1 cells. MiR-221-5p was a target of circSCAP, and anti-miR-221-5p largely reversed si-circSCAP-induced effects in ox-LDL-induced THP-1 cells. PDE3B was a target of miR-221-5p, and PDE3B overexpression largely counteracted miR-221-5p accumulation-mediated effects in ox-LDL-induced THP-1 cells. NF-κB signaling pathway was regulated by circSCAP/miR-221-5p/PDE3B axis in ox-LDL-induced THP-1 cells. In conclusion, circSCAP facilitated lipid accumulation, inflammation, and oxidative stress in ox-LDL-induced THP-1 macrophages by regulating miR-221-5p/PDE3B axis.

SIRT1 regulates sphingolipid metabolism and neural differentiation of mouse embryonic stem cells through c-Myc-SMPDL3B.

Sphingolipids are important structural components of cell membranes and prominent signaling molecules controlling cell growth, differentiation, and apoptosis. Sphingolipids are particularly abundant in the brain, and defects in sphingolipid degradation are associated with several human neurodegenerative diseases. However, molecular mechanisms governing sphingolipid metabolism remain unclear. Here, we report that sphingolipid degradation is under transcriptional control of SIRT1, a highly conserved mammalian NAD+-dependent protein deacetylase, in mouse embryonic stem cells (mESCs). Deletion of SIRT1 results in accumulation of sphingomyelin in mESCs, primarily due to reduction of SMPDL3B, a GPI-anchored plasma membrane bound sphingomyelin phosphodiesterase. Mechanistically, SIRT1 regulates transcription of Smpdl3b through c-Myc. Functionally, SIRT1 deficiency-induced accumulation of sphingomyelin increases membrane fluidity and impairs neural differentiation in vitro and in vivo. Our findings discover a key regulatory mechanism for sphingolipid homeostasis and neural differentiation, further imply that pharmacological manipulation of SIRT1-mediated sphingomyelin degradation might be beneficial for treatment of human neurological diseases.

All cells in the brain start life as stem cells which are yet to have a defined role in the body. A wide range of molecules and chemical signals guide stem cells towards a neuronal fate, including a group of molecules called sphingolipids. These molecules sit in the membrane surrounding the cell and play a pivotal role in a number of processes which help keep the neuronal cell healthy. Various enzymes work together to break down sphingolipids and remove them from the membrane. Defects in these enzymes can result in excess levels of sphingolipids, which can lead to neurodegenerative diseases, such as Alzheimer's, Parkinson's and Huntington's disease. But how these enzymes are used and controlled during neuronal development is still somewhat of a mystery. To help answer this question, Fan et al. studied an enzyme called SIRT1 which has been shown to alleviate symptoms in animal models of neurodegenerative diseases. Stem cells were extracted from a mouse embryo lacking the gene for SIRT1 and cultured in the laboratory. These faulty cells were found to have superfluous amounts of sphingolipids, which made their membranes more fluid and reduced their ability to develop into neuronal cells. Further investigation revealed that SIRT1 regulates the degradation of sphingolipids by promoting the production of another enzyme called SMPDL3B. Fan et al. also found that when female mice were fed a high-fat diet, this caused sphingolipids to accumulate in their embryos which lacked the gene for SIRT1; this, in turn, impaired the neural development of their offspring. These findings suggest that targeting SIRT1 may offer new strategies for treating neurological diseases. The discovery that embryos deficient in SIRT1 are sensitive to high-fat diets implies that activating this enzyme might attenuate some of the neonatal complications associated with maternal obesity.

Phosphodiesterase 2A and 3B variants are associated with primary aldosteronism.

Familial primary aldosteronism (PA) is rare and mostly diagnosed in early-onset hypertension (HT). However, 'sporadic' bilateral adrenal hyperplasia (BAH) is the most frequent cause of PA and remains without genetic etiology in most cases. Our aim was to investigate new genetic defects associated with BAH and PA. We performed whole-exome sequencing (paired blood and adrenal tissue) in six patients with PA caused by BAH that underwent unilateral adrenalectomy. Additionally, we conducted functional studies in adrenal hyperplastic tissue and transfected cells to confirm the pathogenicity of the identified genetic variants. Rare germline variants in phosphodiesterase 2A (PDE2A) and 3B (PDE3B) genes were identified in three patients. The PDE2A heterozygous variant (p.Ile629Val) was identified in a patient with BAH and early-onset HT at 13 years of age. Two PDE3B heterozygous variants (p.Arg217Gln and p.Gly392Val) were identified in patients with BAH and HT diagnosed at 18 and 33 years of age, respectively. A strong PDE2A staining was found in all cases of BAH in zona glomerulosa and/or micronodules (that were also positive for CYP11B2). PKA activity in frozen tissue was significantly higher in BAH from patients harboring PDE2A and PDE3B variants. PDE2A and PDE3B variants significantly reduced protein expression in mutant transfected cells compared to WT. Interestingly, PDE2A and PDE3B variants increased SGK1 and SCNN1G/ENaCg at mRNA or protein levels. In conclusion, PDE2A and PDE3B variants were associated with PA caused by BAH. These novel genetic findings expand the spectrum of genetic etiologies of PA.

Identification and functional study of genetic polymorphisms in cyclic nucleotide phosphodiesterase 3A (PDE3A).

Phosphodiesterase 3A (PDE3A) is an enzyme that plays an important role in the regulation of cyclic adenosine monophosphate (cAMP)-mediated intracellular signaling in cardiac myocytes and platelets. PDE3A hydrolyzes cAMP, which results in a decrease in intracellular cAMP levels and leads to platelet activation. Whole-exome sequencing of 50 DNA samples from a healthy Korean population revealed a total of 13 single nucleotide polymorphisms including five missense variants, D12N, Y497C, H504Q, C707R, and A980V. Recombinant proteins for the five variants of PDE3A (and wild-type protein) were expressed in a FreeStyle 293 expression system with site-directed mutagenesis. The expression of the recombinant PDE3A proteins was confirmed with Western blotting. Catalytic activity of the PDE3A missense variants and wild-type enzyme was measured with a PDE-based assay. Effects of the missense variants on the inhibition of PDE3A activity by cilostazol were also investigated. All variant proteins showed reduced activity (33-53%; p < .0001) compared to the wild-type protein. In addition, PDE3A activity was inhibited by cilostazol in a dose-dependent manner and was further suppressed in the missense variants. Specifically, the PDE3A Y497C showed significantly reduced activity, consistent with the predictions of in silico analyses. The present study provides evidence that individuals carrying the PDE3A Y497C variant may have lower enzyme activity for cAMP hydrolysis, which could cause interindividual variation in cAMP-mediated physiological functions.

Polygenetic-Risk Scores for A Glaucoma Risk Interact with Blood Pressure, Glucose Control, and Carbohydrate Intake.

Glaucoma, a leading cause of blindness, has multifactorial causes, including environmental and genetic factors. We evaluated genetic risk factors of glaucoma with gene-gene interaction and explored modifications of genetic risk with gene-lifestyles interaction in adults >40 years. The present study included 377 subjects with glaucoma and 47,820 subjects without glaucoma in a large-scale hospital-based cohort study from 2004 to 2013. The presence of glaucoma was evaluated by a diagnostic questionnaire evaluated by a doctor. The genome-wide association study was performed to identify genetic variants associated with glaucoma risk. Food intake was assessed using a semiquantitative food frequency questionnaire. We performed generalized multifactor dimensionality reduction analysis to construct polygenetic-risk score (PRS) and explored gene × nutrient interaction. PRS of the best model included LIM-domain binding protein-2 (LDB2) rs3763969, cyclin-dependent kinase inhibitor 2B (CDKN2B) rs523096, ABO rs2073823, phosphodiesterase-3A (PDE3A) rs12314390, and cadherin 13 (CDH13) rs12449180. Glaucoma risk in the high-PRS group was 3.02 times that in the low-PRS group after adjusting for confounding variables. For those with low serum glucose levels (<126 mg/dL), but not for those with high serum glucose levels, glaucoma risk in the high-PRS group was 3.16 times that in the low-PRS group. In those with high carbohydrate intakes (≥70%), but not in those with low carbohydrate intakes, glaucoma risk was 3.74 times higher in the high-PRS group than in the low-PRS group. The glaucoma risk was 3.87 times higher in the high-PRS group than in the low-PRS group only in a low balanced diet intake. In conclusion, glaucoma risk increased by three-fold in adults with a high PRS, and it can be reduced by good control of serum glucose concentrations and blood pressure (BP) with a balanced diet intake. These results can be applied to precision nutrition to reduce glaucoma risk.