Molecular Aspects of Secretory Granule Exocytosis by Neurons and Endocrine Cells

Neuronal communication and endocrine signaling are fundamental for integrating the function of tissues and cells in the body. Hormones released by endocrine cells are transported to the target cells through the circulation. By contrast, transmitter release from neurons occurs at specialized intercellular junctions, the synapses. Nevertheless, the mechanisms by which signal molecules are synthesized, stored, and eventually secreted by neurons and endocrine cells are very similar. Neurons and endocrine cells have in common two different types of secretory organelles, indicating the presence of two distinct secretory pathways. The synaptic vesicles of neurons contain excitatory or inhibitory neurotransmitters, whereas the secretory granules (also referred to as dense core vesicles, because of their electron dense content) are filled with neuropeptides and amines. In endocrine cells, peptide hormones and amines predominate in secretory granules. The function and content of vesicles, which share antigens with synaptic vesicles, are unknown for most endocrine cells. However, in B cells of the pancreatic islet, these vesicles contain GABA, which may be involved in intrainsular signaling.' Exocytosis of both synaptic vesicles and secretory granules is controlled by cytoplasmic calcium. However, the precise mechanisms of the subsequent steps, such as docking of vesicles and fusion of their membranes with the plasma membrane, are still incompletely understood. This contribution summarizes recent observations that elucidate components in neurons and endocrine cells involved in exocytosis. Emphasis is put on the intracellular aspects of the release of secretory granules that recently have been analyzed in detail

An Analytical Pipeline for Quantitative Characterization of Dietary Intake:Application To Assess Grape Intake

Lack of accurate dietary assessment in free-living populations requires discovery of new biomarkers reflecting food intake qualitatively and quantitatively to objectively evaluate effects of diet on health. We provide a proof-of-principle for an analytical pipeline to identify quantitative dietary biomarkers. Tartaric acid was identified by nuclear magnetic resonance spectroscopy as a dose-responsive urinary biomarker of grape intake and subsequently quantified in volunteers following a series of 4-day dietary interventions incorporating 0 g/day, 50 g/day, 100 g/day, and 150 g/day of grapes in standardized diets from a randomized controlled clinical trial. Most accurate quantitative predictions of grape intake were obtained in 24 h urine samples which have the strongest linear relationship between grape intake and tartaric acid excretion (r² = 0.90). This new methodological pipeline for estimating nutritional intake based on coupling dietary intake information and quantified nutritional biomarkers was developed and validated in a controlled dietary intervention study, showing that this approach can improve the accuracy of estimating nutritional intakes

Comparison between polyethylene glycol- and polyethylenimine-mediated transformation of Aspergillus nidulans

ArticleCURRENT GENETICS. 54(2):95-103(2008)journal articl

GluN2B-Selective N-Methyl-d-aspartate (NMDA) Receptor Antagonists Derived from 3-Benzazepines: Synthesis and Pharmacological Evaluation of Benzo[7]annulen-7-amines

Given their high neuroprotective potential, ligands that block GluN2B-containing N-methyl-d-aspartate (NMDA) receptors by interacting with the ifenprodil binding site located on the GluN2B subunit are of great interest for the treatment of various neuronal disorders. In this study, a novel class of GluN2B-selective NMDA receptor antagonists with the benzo[7]annulene scaffold was prepared and pharmacologically evaluated. The key intermediate, N-(2-methoxy-5-oxo-6,7,8,9-tetrahydro-5H-benzo[7]annulen-7-yl)acetamide (11), was obtained by cyclization of 3-acetamido-5-(3-methoxyphenyl)pentanoic acid (10 b). The final reaction steps comprise hydrolysis of the amide, reduction of the ketone, and reductive alkylation, leading to cis- and trans-configured 7-(ω-phenylalkylamino)benzo[7]annulen-5-ols. High GluN2B affinity was observed with cis-configured γ-amino alcohols substituted with a 3-phenylpropyl moiety at the amino group. Removal of the benzylic hydroxy moiety led to the most potent GluN2B antagonists of this series: 2-methoxy-N-(3-phenylpropyl)-6,7,8,9-tetrahydro-5H-benzo[7]annulen-7-amine (20 a, Ki=10 nm) and 2-methoxy-N-methyl-N-(3-phenylpropyl)-6,7,8,9-tetrahydro-5H-benzo[7]annulen-7-amine (23 a, Ki=7.9 nm). The selectivity over related receptors (phencyclidine binding site of the NMDA receptor, σ1 and σ2 receptors) was recorded. In a functional assay measuring the cytoprotective activity of the benzo[7]annulenamines, all tested compounds showed potent NMDA receptor antagonistic activity. Cytotoxicity induced via GluN2A subunit-containing NMDA receptors was not inhibited by the new ligands

Rabphilin regulates SNARE-dependent re-priming of synaptic vesicles for fusion

Synaptic vesicle fusion is catalyzed by assembly of synaptic SNARE complexes, and is regulated by the synaptic vesicle GTP-binding protein Rab3 that binds to RIM and to rabphilin. RIM is a known physiological regulator of fusion, but the role of rabphilin remains obscure. We now show that rabphilin regulates recovery of synaptic vesicles from use-dependent depression, probably by a direct interaction with the SNARE protein SNAP-25. Deletion of rabphilin dramatically accelerates recovery of depressed synaptic responses; this phenotype is rescued by viral expression of wild-type rabphilin, but not of mutant rabphilin lacking the second rabphilin C(2) domain that binds to SNAP-25. Moreover, deletion of rabphilin also increases the size of synaptic responses in synapses lacking the vesicular SNARE protein synaptobrevin in which synaptic responses are severely depressed. Our data suggest that binding of rabphilin to SNAP-25 regulates exocytosis of synaptic vesicles after the readily releasable pool has either been physiologically exhausted by use-dependent depression, or has been artificially depleted by deletion of synaptobrevin