Glutamate signaling and neuroligin/neurexin adhesion play opposing roles that are mediated by major histocompatibility complex I molecules in cortical synapse formation.

Although neurons release neurotransmitter before contact, the role for this release in synapse formation remains unclear. Cortical synapses do not require synaptic vesicle release for formation , yet glutamate clearly regulates glutamate receptor trafficking and induces spine formation . Using a culture system to dissect molecular mechanisms, we found that glutamate rapidly decreases synapse density specifically in young cortical neurons in a local and calcium-dependent manner through decreasing NMDAR transport and surface expression as well as co-transport with neuroligin (NL1).

MHCI requires MEF2 transcription factors to negatively regulate synapse density during development and in disease.

Major histocompatibility complex class I (MHCI) molecules negatively regulate cortical connections and are implicated in neurodevelopmental disorders, including autism spectrum disorders and schizophrenia. However, the mechanisms that mediate these effects are unknown. Here, we report a novel MHCI signaling pathway that requires the myocyte enhancer factor 2 (MEF2) transcription factors.

Neuroligins help dendrites keep up with the Joneses.

A function for neuroligins in synapse formation has been controversial owing to conflicting data from work and knockout mice. A study now reconciles previous results, showing that cell-to-cell variability in neuroligin-1 expression, which mediates intercellular competition for presynaptic inputs, regulates synapse density and spinogenesis.

Dynamic changes in cytosolic and mitochondrial ATP levels in pancreatic acinar cells.

Background & Aims: Previous studies of pancreatic acinar cells characterized the effects of Ca(2+)-releasing secretagogues and substances, inducing acute pancreatitis on mitochondrial Ca(2+), transmembrane potential, and NAD(P)H, but dynamic measurements of the crucial intracellular adenosine triphosphate (ATP) levels have not been reported. Here we characterized the effects of these agents on ATP levels in the cytosol and mitochondria.

Methods: ATP levels were monitored using cytosolic- or mitochondrial-targeted luciferases.

Neuroligin1: a cell adhesion molecule that recruits PSD-95 and NMDA receptors by distinct mechanisms during synaptogenesis.

Background: The cell adhesion molecule pair neuroligin1 (Nlg1) and beta-neurexin (beta-NRX) is a powerful inducer of postsynaptic differentiation of glutamatergic synapses in vitro. Because Nlg1 induces accumulation of two essential components of the postsynaptic density (PSD) - PSD-95 and NMDA receptors (NMDARs) - and can physically bind PSD-95 and NMDARs at mature synapses, it has been proposed that Nlg1 recruits NMDARs to synapses through its interaction with PSD-95. However, PSD-95 and NMDARs are recruited to nascent synapses independently and it is not known if Nlg1 accumulates at synapses before these PSD proteins.

ATP depletion inhibits Ca2+ release, influx and extrusion in pancreatic acinar cells but not pathological Ca2+ responses induced by bile.

Here, we describe novel mechanisms limiting a toxic cytosolic Ca(2+) rise during adenosine 5'-triphosphate (ATP) depletion. We studied the effect of ATP depletion on Ca(2+) signalling in mouse pancreatic acinar cells. Measurements of ATP in isolated cells after adenovirus-mediated expression of firefly luciferase revealed that the cytosolic ATP concentration fell from approximately 1 mM to near zero after treatment with oligomycin plus iodoacetate.

A gain-of-function mutant of Munc18-1 stimulates secretory granule recruitment and exocytosis and reveals a direct interaction of Munc18-1 with Rab3.

Munc18-1 plays a crucial role in regulated exocytosis in neurons and neuroendocrine cells through modulation of vesicle docking and membrane fusion. The molecular basis for Munc18 function is still unclear, as are the links with Rabs and SNARE [SNAP (soluble N-ethylmaleimide-sensitive factor-attachment protein) receptor] proteins that are also required. Munc18-1 can bind to SNAREs through at least three modes of interaction, including binding to the closed conformation of syntaxin 1.

Caspase-8-mediated apoptosis induced by oxidative stress is independent of the intrinsic pathway and dependent on cathepsins.

Cell-death programs executed in the pancreas under pathological conditions remain largely undetermined, although the severity of experimental pancreatitis has been found to depend on the ratio of apoptosis to necrosis. We have defined mechanisms by which apoptosis is induced in pancreatic acinar cells by the oxidant stressor menadione. Real-time monitoring of initiator caspase activity showed that caspase-9 (66% of cells) and caspase-8 (15% of cells) were activated within 30 min of menadione administration, but no activation of caspase-2, -10, or -12 was detected.

Activation of trypsinogen in large endocytic vacuoles of pancreatic acinar cells.

The intracellular activation of trypsinogen, which is both pH- and calcium-dependent, is an important early step in the development of acute pancreatitis. The cellular compartment in which trypsinogen activation occurs currently is unknown. We therefore investigated the site of intracellular trypsinogen activation by using an established cellular model of acute pancreatitis: supramaximal stimulation of pancreatic acinar cells with cholecystokinin.

Effects of secretagogues and bile acids on mitochondrial membrane potential of pancreatic acinar cells: comparison of different modes of evaluating DeltaPsim.

In this study, we investigated the effects of secretagogues and bile acids on the mitochondrial membrane potential of pancreatic acinar cells. We measured the mitochondrial membrane potential using the tetramethylrhodamine-based probes tetramethylrhodamine ethyl ester and tetramethylrhodamine methyl ester. At low levels of loading, these indicators appeared to have a low sensitivity to the uncoupler carbonyl cyanide m-chlorophenylhydrazone, and no response was observed to even high doses of cholecystokinin.