TI-VAMP/VAMP7 is the SNARE of secretory lysosomes contributing to ATP secretion from astrocytes

Background information

ATP is the main transmitter stored and released from astrocytes under physiological and pathological conditions. Morphological and functional evidence suggest that besides secretory granules, secretory lysosomes release ATP. However, the molecular mechanisms involved in astrocytic lysosome fusion remain still unknown.

Results

In the present study, we identify tetanus neurotoxin‐insensitive vesicle‐associated membrane protein (TI‐VAMP, also called VAMP7) as the vesicular SNARE which mediates secretory lysosome exocytosis, contributing to release of both ATP and cathepsin B from glial cells. We also demonstrate that fusion of secretory lysosomes is triggered by slow and locally restricted calcium elevations, distinct from calcium spikes which induce the fusion of glutamate‐containing clear vesicles. Downregulation of TI‐VAMP/VAMP7 expression inhibited the fusion of ATP‐storing vesicles and ATP‐mediated calcium wave propagation. TI‐VAMP/VAMP7 downregulation also significantly reduced secretion of cathepsin B from glioma.

Conclusions

Given that sustained ATP release from glia upon injury greatly contributes to secondary brain damage and cathepsin B plays a critical role in glioma dissemination, TI‐VAMP silencing can represent a novel strategy to control lysosome fusion in pathological conditions.     

Fused tricyclic mGluR1 antagonists for the treatment of neuropathic pain

A series of fused tricyclic mGluR1 antagonists containing a pyridone ring were synthesized. In vitro, these antagonists were potent against both human and rat isozymes, as well as selective for inhibiting mGluR1 over mGluR5. When dosed orally, several examples were active in vivo in a rat SNL test.     

Distinct Genetic and Functional Traits of Human Intestinal Prevotella copri Strains Are Associated with Different Habitual Diets

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H+ pump-dependent changes in membrane voltage are an early mechanism necessary and sufficient to induce Xenopus tail regeneration

In many systems, ion flows and long-term endogenous voltage gradients regulate patterning events, but molecular details remain mysterious. To establish a mechanistic link between biophysical events and regeneration, we investigated the role of ion transport during Xenopus tail regeneration. We show that activity of the V-ATPase H(+) pump is required for regeneration but not wound healing or tail development. The V-ATPase is specifically upregulated in existing wound cells by 6 hours post-amputation. Pharmacological or molecular genetic loss of V-ATPase function and the consequent strong depolarization abrogates regeneration without inducing apoptosis. Uncut tails are normally mostly polarized, with discrete populations of depolarized cells throughout. After amputation, the normal regeneration bud is depolarized, but by 24 hours post-amputation becomes rapidly repolarized by the activity of the V-ATPase, and an island of depolarized cells appears just anterior to the regeneration bud. Tail buds in a non-regenerative ;refractory' state instead remain highly depolarized relative to uncut or regenerating tails. Depolarization caused by V-ATPase loss-of-function results in a drastic reduction of cell proliferation in the bud, a profound mispatterning of neural components, and a failure to regenerate. Crucially, induction of H(+) flux is sufficient to rescue axonal patterning and tail outgrowth in otherwise non-regenerative conditions. These data provide the first detailed mechanistic synthesis of bioelectrical, molecular and cell-biological events underlying the regeneration of a complex vertebrate structure that includes spinal cord, and suggest a model of the biophysical and molecular steps underlying tail regeneration. Control of H(+) flows represents a very important new modality that, together with traditional biochemical approaches, may eventually allow augmentation of regeneration for therapeutic applications.     

Fragment-based approaches to enzyme inhibition

Fragment-based approaches have provided a new paradigm for small-molecule drug discovery. The methodology is complementary to high-throughput screening approaches, starting from fragments of low molecular complexity and high ligand efficiency, and building up to more potent inhibitors. The approach, which depends heavily on a number of biophysical techniques, is now being taken up by more groups in both industry and academia. This article describes key aspects of the process and highlights recent developments and applications.     

Neuronal oscillator robustness to multiple global perturbations

Neuronal activity depends on ion channels and biophysical processes that are strongly and differentially sensitive to physical variables such as temperature and pH. Nonetheless, neuronal oscillators can be surprisingly resilient to perturbations in these variables. We study a three-neuron pacemaker ensemble that drives the pyloric rhythm of the crab, Cancer borealis. These crabs routinely experience a number of global perturbations, including changes in temperature and pH. Although pyloric oscillations are robust to such changes, for sufficiently large deviations the rhythm reversibly breaks down. As temperature increases beyond a tipping point, oscillators transition to silence. Acidic pH deviations also show tipping points, with a reliable transition first to tonic spiking, then to silence. Surprisingly, robustness to perturbations in pH only moderately affects temperature robustness. Consistent with high animal-to-animal variability in biophysical circuit parameters, tipping points in temperature and pH vary across animals. However, the ordering and discrete classes of transitions at critical points are conserved. This implies that qualitative oscillator dynamics are preserved across animals despite high quantitative parameter variability. A universal model of bursting dynamics predicts the existence of these transition types and the order in which they occur.     

Hormonal Responses to Water Deficit in Cambial Tissues of Populus alba L.

Changes in the concentrations of bioactive gibberellins and abscisic acid in the cambial region of white poplar (Populus alba L.) were investigated in 1-year-old plants, to highlight how these phytohormone signals are modulated in response to water deficit. Plants were cultivated in pots outdoor and, at the time of maximum cambial growth (T ₀), irrigation was withdrawn for 8 days, inducing a mild water deficit, thus mimicking a condition that is recurrent in Mediterranean climates when white poplar attains its maximum growth rate. The water deficit was suspended by resuming irrigation (T _max) throughout a recovery period of 2 weeks (T _rec). Cambial tissues were sampled at T ₀, T _max, and T _rec. Significant changes of leaf and stem relative water content, leaf water potential, stomatal conductance, transpiration, carbon assimilation, stem shrinkage, and leaf number were induced by soil water shortage, which also negatively affected cambium development. Nevertheless, these responses were almost fully reversed following the resumption of irrigation. Water deficit induced the accumulation of large amounts of abscisic acid in cambial tissues, but the hormone was brought back to pre-stress levels after the recovery period. With regard to bioactive gibberellins, GA₁ was several folds more abundant than GA₄ and reached the greatest level in the plants recovering from the water status imbalance. The possible functions of gibberellins and abscisic acid in the response of cambial tissues to water deficit are discussed in view of the known physiological roles and molecular mechanisms of action of these hormonal signals.