Role of Complexin 2 in the regulation of hormone secretion from the islet of Langerhans.

Regulated secretion of insulin from β-cells, glucagon from α-cells, and somatostatin from δ-cells is necessary for the maintenance of glucose homeostasis. The release of these hormones from pancreatic islet cells requires the assembly and disassembly of the SNARE protein complex to control vesicle fusion and exocytosis. Complexin 2 (Cplx 2) is a small soluble synaptic protein that participates in the priming and release steps of vesicle fusion.

Primary cilia control glucose homeostasis via islet paracrine interactions.

Pancreatic islets regulate glucose homeostasis through coordinated actions of hormone-secreting cells. What underlies the function of the islet as a unit is the close approximation and communication among heterogeneous cell populations, but the structural mediators of islet cellular cross talk remain incompletely characterized. We generated mice specifically lacking β-cell primary cilia, a cellular organelle that has been implicated in regulating insulin secretion, and found that the β-cell cilia are required for glucose sensing, calcium influx, insulin secretion, and cross regulation of α- and δ-cells.

The Role of Free Oxygen Radicals in Lasting Hyperexcitability of Rat Subicular Neurons After Exposure to General Anesthesia During Brain Development.

A large number of preclinical studies have established that general anesthetics (GAs) may cause neurodevelopmental toxicity in rodents and nonhuman primates, which is followed by long-term cognitive deficits. The subiculum, the main output structure of hippocampal formation, is one of the brain regions most sensitive to exposure to GAs at the peak of synaptogenesis (i.e.

The role of T-type calcium channels in the subiculum: to burst or not to burst?

Key Points: Pharmacological, molecular and genetic data indicate a prominent role of low-voltage-activated T-type calcium channels (T-channels) in the firing activity of both pyramidal and inhibitory interneurons in the subiculum. Pharmacological inhibition of T-channels switched burst firing with lower depolarizing stimuli to regular spiking, and fully abolished hyperpolarization-induced burst firing. Our molecular studies showed that Ca 3.

Virgin Beta Cells Persist throughout Life at a Neogenic Niche within Pancreatic Islets.

Postnatal maintenance or regeneration of pancreatic beta cells is considered to occur exclusively via the replication of existing beta cells, but clinically meaningful restoration of human beta cell mass by proliferation has never been achieved. We discovered a population of immature beta cells that is present throughout life and forms from non-beta precursors at a specialized micro-environment or "neogenic niche" at the islet periphery. These cells express insulin, but lack other key beta cell markers, and are transcriptionally immature, incapable of sensing glucose, and unable to support calcium influx.

Comprehensive alpha, beta and delta cell transcriptomes reveal that ghrelin selectively activates delta cells and promotes somatostatin release from pancreatic islets.

Objective: Complex local crosstalk amongst endocrine cells within the islet ensures tight coordination of their endocrine output. This is illustrated by the recent demonstration that the negative feedback control by delta cells within pancreatic islets determines the homeostatic set-point for plasma glucose during mouse postnatal development. However, the close association of islet endocrine cells that facilitates paracrine crosstalk also complicates the distinction between effects mediated directly on beta cells from indirect effects mediated via local intermediates, such as somatostatin from delta cells.

General Anesthesia Causes Epigenetic Histone Modulation of c-Fos and Brain-derived Neurotrophic Factor, Target Genes Important for Neuronal Development in the Immature Rat Hippocampus.

Background: Early postnatal exposure to general anesthesia (GA) may be detrimental to brain development, resulting in long-term cognitive impairments. Older literature suggests that in utero exposure of rodents to GA causes cognitive impairments in the first-generation as well as in the second-generation offspring never exposed to GA. Thus, the authors hypothesize that transient exposure to GA during critical stages of synaptogenesis causes epigenetic changes in chromatin with deleterious effects on transcription of target genes crucial for proper synapse formation and cognitive development.

Hyperexcitability of rat thalamocortical networks after exposure to general anesthesia during brain development.

Prevailing literature supports the idea that common general anesthetics (GAs) cause long-term cognitive changes and neurodegeneration in the developing mammalian brain, especially in the thalamus. However, the possible role of GAs in modifying ion channels that control neuronal excitability has not been taken into consideration. Here we show that rats exposed to GAs at postnatal day 7 display a lasting reduction in inhibitory synaptic transmission, an increase in excitatory synaptic transmission, and concomitant increase in the amplitude of T-type calcium currents (T-currents) in neurons of the nucleus reticularis thalami (nRT).

Inhibition of CaV3.2 T-type calcium channels in peripheral sensory neurons contributes to analgesic properties of epipregnanolone.

Rationale: T-type calcium channels (T-channels) play an important role in controlling excitability of nociceptors. We have previously shown that a synthetic series of 5β-reduced steroids induce a voltage-dependent blockade of T-currents in rat dorsal root ganglia (DRG) cells in vitro and induce potent analgesia to thermal stimuli in rats in vivo (Mol Pharmacol 66:1223-1235, 2004).

Objectives: Here, we investigated the effects of the endogenous 5β-reduced neuroactive steroid molecule, epipregnanolone [(3β,5β)-3-hydroxypregnan-20-one], on peripheral nociception.

Reversal of neuropathic pain in diabetes by targeting glycosylation of Ca(V)3.2 T-type calcium channels.

It has been established that Ca(V)3.2 T-type voltage-gated calcium channels (T-channels) play a key role in the sensitized (hyperexcitable) state of nociceptive sensory neurons (nociceptors) in response to hyperglycemia associated with diabetes, which in turn can be a basis for painful symptoms of peripheral diabetic neuropathy (PDN). Unfortunately, current treatment for painful PDN has been limited by nonspecific systemic drugs with significant side effects or potential for abuse.

Inhibition of T-type calcium current in rat thalamocortical neurons by isoflurane.

Thalamocortical (TC) neurons provide the major sensory input to the mammalian somatosensory cortex. Decreased activity of these cells may be pivotal in the ability of general anesthetics to induce loss of consciousness and promote sleep (hypnosis). T-type voltage-gated calcium currents (T-currents) have a key function regulating the cellular excitability of TC neurons and previous studies have indicated that volatile general anesthetics may alter the excitability of these neurons.

Type 2 corticotropin-releasing factor receptor in the ventromedial nucleus of hypothalamus is critical in regulating feeding and lipid metabolism in white adipose tissue.

Ventromedial nucleus of hypothalamus (VMH) plays a critical role in regulating feeding and energy metabolism. The nucleus expresses high levels of the type 2 corticotropin-releasing factor receptor (CRFR2) and receives prominent innervation of nerve fibers containing Urocortin 3 (Ucn 3), an endogenous ligand of the receptor. In the present study, we showed that mice deficient in Ucn 3 had elevated basal feeding and increased nocturnal food intake after overnight fasting compared with the wild-type (WT) littermates.

Free radical signalling underlies inhibition of CaV3.2 T-type calcium channels by nitrous oxide in the pain pathway.

Nitrous oxide (N2O, laughing gas) has been used as an anaesthetic and analgesic for almost two centuries, but its cellular targets remain unclear. Here, we present a molecular mechanism of nitrous oxide's selective inhibition of CaV3.2 low-voltage-activated (T-type) calcium channels in pain pathways.

Distinct structural and functional roles of conserved residues in the first extracellular domain of receptors for corticotropin-releasing factor and related G-protein-coupled receptors.

The G-protein-coupled receptor B1 family includes corticotropin-releasing factor (CRF), growth hormone-releasing hormone, incretin, and pituitary adenylate cyclase-activating polypeptide receptors. The three-dimensional NMR structure of the first extracellular domain (ECD1) of CRF receptor 2beta (CRF-R2beta), free and complexed with astressin, comprises a Sushi domain. This domain is stabilized in part by a salt bridge between Asp(65) and Arg(101).

Structure of the N-terminal domain of a type B1 G protein-coupled receptor in complex with a peptide ligand.

The corticotropin releasing factor (CRF) family of ligands and their receptors coordinate endocrine, behavioral, autonomic, and metabolic responses to stress and play additional roles within the cardiovascular, gastrointestinal, and other systems. The actions of CRF and the related urocortins are mediated by activation of two receptors, CRF-R1 and CRF-R2, belonging to the B1 family of G protein-coupled receptors. The short-consensus-repeat fold (SCR) within the first extracellular domain (ECD1) of the CRF receptor(s) comprises the major ligand binding site and serves to dock a peptide ligand via its C-terminal segment, thus positioning the N-terminal segment to interact with the receptor's juxtamembrane domains to activate the receptor.

Stressin1-A, a potent corticotropin releasing factor receptor 1 (CRF1)-selective peptide agonist.

The potencies and selectivity of peptide CRF antagonists is increased through structural constraints, suggesting that the resulting ligands assume distinct conformations when interacting with CRF1 and CRF2 receptors. To develop selective CRF receptor agonists, we have scanned the sequence -Gln-Ala-His-Ser-Asn-Arg- (residues 30-35 of [DPhe12,Nle21,38]Ac-hCRF4-41) with an i-(i+3) bridge consisting of the Glui-Xaa-Xbb-Lysi+3 scaffold, where residues i=30, 31, and 32. When i=31, stressin1-A, a potent CRF1 receptor-selective agonist was generated.

A soluble mouse brain splice variant of type 2alpha corticotropin-releasing factor (CRF) receptor binds ligands and modulates their activity.

Peptides of the corticotropin-releasing factor (CRF) family signal through the activation of two receptors, CRF receptor type 1 (CRFR1) and type 2 (CRFR2), both of which exist as multiple splice variants. We have identified a cDNA from mouse brain encoding a splice variant, soluble CRFR2alpha (sCRFR2alpha), in which exon 6 is deleted from the gene encoding CRFR2alpha. Translation of this isoform produces a predicted 143-aa soluble protein.

NMR structure and peptide hormone binding site of the first extracellular domain of a type B1 G protein-coupled receptor.

The corticotropin-releasing factor (CRF) ligand family has diverse effects on the CNS, including the modulation of the stress response. The ligands' effects are mediated by binding to CRF G protein-coupled receptors. We have determined the 3D NMR structure of the N-terminal extracellular domain (ECD1) of the mouse CRF receptor 2beta, which is the major ligand recognition domain, and identified its ligand binding site by chemical-shift perturbation experiments.

MALDI-MS analysis of peptides modified with photolabile arylazido groups.

The ability of MALDI-MS to analyze photolabile arylazido peptide derivatives was investigated. Peptides containing UV-labile p-azidobenzoyl groups were subjected to MALDI-MS analysis in a variety of matrices. As standard MALDI-MS employs a UV laser (337 nm), we investigated conditions that would allow detection of the intact molecule ions for these light-sensitive peptides.

A soluble form of the first extracellular domain of mouse type 2beta corticotropin-releasing factor receptor reveals differential ligand specificity.

The heptahelical receptors for corticotropin-releasing factor (CRF), CRFR1 and CRFR2, display different specificities for CRF family ligands: CRF and urocortin I bind to CRFR1 with high affinity, whereas urocortin II and III bind to this receptor with very low affinities. In contrast, all the urocortins bind with high affinities, and CRF binds with lower affinity to CRFR2. The first extracellular domain (ECD1) of CRFR1 is important for ligand recognition.