Phosphodiesterase 3B Is Localized in Caveolae and Smooth ER in Mouse Hepatocytes and Is Important in the Regulation of Glucose and Lipid Metabolism

Cyclic nucleotide phosphodiesterases (PDEs) are important regulators of signal transduction processes mediated by cAMP and cGMP. One PDE family member, PDE3B, plays an important role in the regulation of a variety of metabolic processes such as lipolysis and insulin secretion. In this study, the cellular localization and the role of PDE3B in the regulation of triglyceride, cholesterol and glucose metabolism in hepatocytes were investigated. PDE3B was identified in caveolae, specific regions in the plasma membrane, and smooth endoplasmic reticulum. In caveolin-1 knock out mice, which lack caveolae, the amount of PDE3B protein and activity were reduced indicating a role of caveolin-1/caveolae in the stabilization of enzyme protein. Hepatocytes from PDE3B knock out mice displayed increased glucose, triglyceride and cholesterol levels, which was associated with increased expression of gluconeogenic and lipogenic genes/enzymes including, phosphoenolpyruvate carboxykinase, peroxisome proliferator-activated receptor γ, sterol regulatory element-binding protein 1c and hydroxyl-3-methylglutaryl coenzyme A reductase. In conclusion, hepatocyte PDE3B is localized in caveolae and smooth endoplasmic reticulum and plays important roles in the regulation of glucose, triglyceride and cholesterol metabolism. Dysregulation of PDE3B could have a role in the development of fatty liver, a condition highly relevant in the context of type 2 diabetes

Expression and Regulation of Cyclic Nucleotide Phosphodiesterases in Human and Rat Pancreatic Islets

As shown by transgenic mouse models and by using phosphodiesterase 3 (PDE3) inhibitors, PDE3B has an important role in the regulation of insulin secretion in pancreatic β-cells. However, very little is known about the regulation of the enzyme. Here, we show that PDE3B is activated in response to high glucose, insulin and cAMP elevation in rat pancreatic islets and INS-1 (832/13) cells. Activation by glucose was not affected by the presence of diazoxide. PDE3B activation was coupled to an increase as well as a decrease in total phosphorylation of the enzyme. In addition to PDE3B, several other PDEs were detected in human pancreatic islets: PDE1, PDE3, PDE4C, PDE7A, PDE8A and PDE10A. We conclude that PDE3B is activated in response to agents relevant for β-cell function and that activation is linked to increased as well as decreased phosphorylation of the enzyme. Moreover, we conclude that several PDEs are present in human pancreatic islets

Re-imagining bisexuality and Christianity: the negotiation of Christianity in the lives of bisexual women and men

Research exploring non-heterosexual sexuality and Christianity has tended to conflate ‘lesbian and gay’, with ‘bisexual’, effacing the latter. This article explores how bisexual women and men in particular understand their Christianity, where they have been denied access to institutionalised Christianity and have re-imagined their faith. I examine how bisexuality is understood by popular Christian denominations and how respondents challenge these standpoints. The respondents reshaped their faith to be more inclusive of bisexuality and re-imagined their sexuality to fit with their religious faith. I draw upon data from 80 self-completion questionnaires and 20 in-depth interviews

The Caenorhabditis elegans Elongator Complex Regulates Neuronal α-tubulin Acetylation

Although acetylated α-tubulin is known to be a marker of stable microtubules in neurons, precise factors that regulate α-tubulin acetylation are, to date, largely unknown. Therefore, a genetic screen was employed in the nematode Caenorhabditis elegans that identified the Elongator complex as a possible regulator of α-tubulin acetylation. Detailed characterization of mutant animals revealed that the acetyltransferase activity of the Elongator is indeed required for correct acetylation of microtubules and for neuronal development. Moreover, the velocity of vesicles on microtubules was affected by mutations in Elongator. Elongator mutants also displayed defects in neurotransmitter levels. Furthermore, acetylation of α-tubulin was shown to act as a novel signal for the fine-tuning of microtubules dynamics by modulating α-tubulin turnover, which in turn affected neuronal shape. Given that mutations in the acetyltransferase subunit of the Elongator (Elp3) and in a scaffold subunit (Elp1) have previously been linked to human neurodegenerative diseases, namely Amyotrophic Lateral Sclerosis and Familial Dysautonomia respectively highlights the importance of this work and offers new insights to understand their etiology

Understanding the Role of Hyponitrite in Nitric Oxide Reduction

Herein, we review the preparation and coordination chemistry of cis and trans isomers of hyponitrite, [N2O2](2-). Hyponitrite is known to bind to metals via a variety of bonding modes. In fact, at least eight different bonding modes have been observed, which is remarkable for such a simple ligand. More importantly, it is apparent that the cis isomer of hyponitrite is more reactive than the trans isomer because the barrier of N2O elimination from cis-hyponitrite is lower than that of trans-hyponitrite. This observation may have important mechanistic implications for both heterogeneous NOx reduction catalysts and NO reductase. However, our understanding of the hyponitrite ligand has been limited by the lack of a general route to this fragment, and most instances of its formation have been serendipitous

Le rôle de l’oxygène dans les composés complexes

L’oxygène possède la remarquable propriété de pouvoir se lier de façon très forte à d’autres atomes. Cette propriété est en rapport avec sa structure électronique et orbitale et aussi avec son électronégativité. La possibilité de former des liaisons donneurs σ et π fait que son état de valence varie de + 2 à — 2. Cela a lieu dans les complexes des métaux de transition aux noyaux 1. MeOn+, 2. MeO2n+, 3. Me2Ou+ Dans tous ces systèmes, grâce aux liaisons π, il y a consolidation du complexe. Ce très fort couplage avec l’oxygène est pourtant cause du changement des propriétés magnétiques des atomes métalliques et marque de façon caractéristique les spectres d’absorption. La structure des composés a été discutée à l’aide de la théorie des orbitales moléculaires. On a montré aussi que cette théorie explique les propriétés magnétiques et optiques des complexes à ce genre de noyau. Le couplage remarquablement fort des spins des atomes dans les noyaux MeOMe permet de parler de « liaison oxygène »