Cyclic AMP, protein kinase A, and phosphodiesterases: proceedings of an international workshop

Compensation between FOXP transcription factors maintains proper striatal function

Spiny projection neurons (SPNs) of the striatum are critical in integrating neurochemical information to coordinate motor and reward-based behavior. Mutations in the regulatory transcription factors expressed in SPNs can result in neurodevelopmental disorders (NDDs). Paralogous transcription factors Foxp1 and Foxp2, which are both expressed in the dopamine receptor 1 (D1) expressing SPNs, are known to have variants implicated in NDDs. Utilizing mice with a D1-SPN-specific loss of Foxp1, Foxp2, or both and a combination of behavior, electrophysiology, and cell-type-specific genomic analysis, loss of both genes results in impaired motor and social behavior as well as increased firing of the D1-SPNs. Differential gene expression analysis implicates genes involved in autism risk, electrophysiological properties, and neuronal development and function. Viral-mediated re-expression of Foxp1 into the double knockouts is sufficient to restore electrophysiological and behavioral deficits. These data indicate complementary roles between Foxp1 and Foxp2 in the D1-SPNs.

ALDOA coordinates PDE3A through the β-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 β-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.

Compensation between FOXP transcription factors maintains proper striatal function

Spiny projection neurons (SPNs) of the striatum are critical in integrating neurochemical information to coordinate motor and reward-based behavior. Mutations in the regulatory transcription factors expressed in SPNs can result in neurodevelopmental disorders (NDDs). Paralogous transcription factors Foxp1 and Foxp2, which are both expressed in the dopamine receptor 1 (D1) expressing SPNs, are known to have variants implicated in NDDs. Utilizing mice with a D1-SPN specific loss of Foxp1, Foxp2, or both and a combination of behavior, electrophysiology, and cell-type specific genomic analysis, loss of both genes results in impaired motor and social behavior as well as increased firing of the D1-SPNs. Differential gene expression analysis implicates genes involved in autism risk, electrophysiological properties, and neuronal development and function. Viral mediated re-expression of Foxp1 into the double knockouts was sufficient to restore electrophysiological and behavioral deficits. These data indicate complementary roles between Foxp1 and Foxp2 in the D1-SPNs.

Pituitary Tumorigenesis-Implications for Management

Pituitary neuroendocrine tumors (PitNETs), the third most common intracranial tumor, are mostly benign. However, some of them may display a more aggressive behavior, invading into the surrounding structures. While they may rarely metastasize, they may resist different treatment modalities. Several major advances in molecular biology in the past few years led to the discovery of the possible mechanisms involved in pituitary tumorigenesis with a possible therapeutic implication. The mutations in the different proteins involved in the Gsa/protein kinase A/c AMP signaling pathway are well-known and are responsible for many PitNETS, such as somatotropinomas and, in the context of syndromes, as the McCune-Albright syndrome, Carney complex, familiar isolated pituitary adenoma (FIPA), and X-linked acrogigantism (XLAG). The other pathways involved are the MAPK/ERK, PI3K/Akt, Wnt, and the most recently studied HIPPO pathways. Moreover, the mutations in several other tumor suppressor genes, such as menin and CDKN1B, are responsible for the MEN1 and MEN4 syndromes and succinate dehydrogenase (SDHx) in the context of the 3PAs syndrome. Furthermore, the pituitary stem cells and miRNAs hold an essential role in pituitary tumorigenesis and may represent new molecular targets for their diagnosis and treatment. This review aims to summarize the different cell signaling pathways and genes involved in pituitary tumorigenesis in an attempt to clarify their implications for diagnosis and management.

Pde8b haploinsufficiency in mice is associated with modest adrenal defects, impaired steroidogenesis, and male infertility, unaltered by concurrent PKA or Wnt activation

PDE8B, PRKAR1A and the Wnt/β-catenin signaling are involved in endocrine disorders. However, how PDEB8B interacts with both Wnt and protein kinase A (PKA) signaling in vivo remains unknown. We created a novel Pde8b knockout mouse line (Pde8b-/-); Pde8b haploinsufficient (Pde8b+/-) mice were then crossed with mice harboring: (1) constitutive beta-catenin activation (Pde8b+/-;ΔCat) and (2) Prkar1a haploinsufficieny (Pde8b+/-;Prkar1a+/-). Adrenals and testes from mice (3-12-mo) were evaluated in addition to plasma corticosterone, aldosterone and Dkk3 concentrations, and the examination of expression of steroidogenesis-, Wnt- and cAMP/PKA-related genes. Pde8b-/- male mice were infertile with down-regulation of the Wnt/β-catenin pathway which did not change significantly in the Pde8b+/-;ΔCat mice. Prkar1a haploinsufficiency also did not change the phenotype significantly. In vitro studies showed that PDE8B knockdown upregulated the Wnt pathway and increased proliferation in CTNNB1-mutant cells, whereas it downregulated the Wnt pathway in PRKAR1A-mutant cells. These data support an overall weak, if any, role for PDE8B in adrenocortical tumorigenesis, even when co-altered with Wnt signaling or PKA upregulation; on the other hand, PDE8B appears to play a significant role in male fertility.

A Tissue-Engineered Human Psoriatic Skin Model to Investigate the Implication of cAMP in Psoriasis: Differential Impacts of Cholera Toxin and Isoproterenol on cAMP Levels of the Epidermis

Pathological and healthy skin models were reconstructed using similar culture conditions according to well-known tissue engineering protocols. For both models, cyclic nucleotide enhancers were used as additives to promote keratinocytes’ proliferation. Cholera toxin (CT) and isoproterenol (ISO), a beta-adrenergic agonist, are the most common cAMP stimulators recommended for cell culture. The aim of this study was to evaluate the impact of either CT or ISO on the pathological characteristics of the dermatosis while producing a psoriatic skin model. Healthy and psoriatic skin substitutes were produced according to the self-assembly method of tissue engineering, using culture media supplemented with either CT (10⁻¹⁰ M) or ISO (10⁻⁶ M). Psoriatic substitutes produced with CT exhibited a more pronounced psoriatic phenotype than those produced with ISO. Indeed, the psoriatic substitutes produced with CT had the thickest epidermis, as well as contained the most proliferating cells and the most altered expression of involucrin, filaggrin, and keratin 10. Of the four conditions under study, psoriatic substitutes produced with CT had the highest levels of cAMP and enhanced expression of adenylate cyclase 9. Taken together, these results suggest that high levels of cAMP are linked to a stronger psoriatic phenotype.

PDE 2015: cAMP Signaling, Protein Kinase A (PKA) and Phosphodiesterases (PDEs): How Genetics Changed the Way We Look at One of the Most Studied Signaling Pathways

This special issue of Hormone and Metabolic Research presents the proceedings of the 4th international workshop (PDE 2015) on cyclic AMP (cAMP)/protein kinase A (PKA) signaling and phosphodiesterases (PDEs). The meeting took place at Erciyes University, in Kayseri, Turkey, (Fig. 1) and followed the previous workshops that were held in Paris, France, and in Bethesda, MD 1 2. We are indebted to the host, one of the newest and most advanced universities in Turkey, an example of how science can be inclusive and bridge not only disciplines, but also cultures. We visited the historic Cappadocia region with its rich Greek heritage, and enjoyed the local food and traditions, as well as the beautiful Ottoman architecture of Kayseri and its surroundings.

Phosphodiesterase Inhibitors as a Therapeutic Approach to Neuroprotection and Repair

A wide diversity of perturbations of the central nervous system (CNS) result in structural damage to the neuroarchitecture and cellular defects, which in turn are accompanied by neurological dysfunction and abortive endogenous neurorepair. Altering intracellular signaling pathways involved in inflammation and immune regulation, neural cell death, axon plasticity and remyelination has shown therapeutic benefit in experimental models of neurological disease and trauma. The second messengers, cyclic adenosine monophosphate (cyclic AMP) and cyclic guanosine monophosphate (cyclic GMP), are two such intracellular signaling targets, the elevation of which has produced beneficial cellular effects within a range of CNS pathologies. The only known negative regulators of cyclic nucleotides are a family of enzymes called phosphodiesterases (PDEs) that hydrolyze cyclic nucleotides into adenosine monophosphate (AMP) or guanylate monophosphate (GMP). Herein, we discuss the structure and physiological function as well as the roles PDEs play in pathological processes of the diseased or injured CNS. Further we review the approaches that have been employed therapeutically in experimental paradigms to block PDE expression or activity and in turn elevate cyclic nucleotide levels to mediate neuroprotection or neurorepair as well as discuss both the translational pathway and current limitations in moving new PDE-targeted therapies to the clinic.

Phosphodiesterase 8B and cyclic AMP signaling in the adrenal cortex

Bilateral adrenocortical hyperplasia (BAH) in humans and mice has been recently linked to phosphodiesterase (PDE) 8B (PDE8B) and 11 (PDE11A) defects. These findings have followed the discovery that defects of primary genes of the cyclic monophosphatase (cAMP) signaling pathway, such as guanine nucleotide binding alpha subunit and PRKAR1A, are involved in the pathogenesis of BAH in humans; complete absence of Prkar1a in the adrenal cortex of mice also led to pathology that mimicked the human disease. Here, we review the most recent findings in human and mouse studies on PDE8B, a cAMP-specific PDE that appears to be highly expressed in the adrenal cortex and whose deficiency may underlie predisposition to BAH and possibly other human diseases.