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Depletion of the endoplasmic reticulum (ER) calcium store triggers translocation of stromal interacting molecule one (STIM1) to the sub-plasmalemmal region and formation of puncta-structures in which STIM1 interacts and activates calcium channels. ATP depletion induced the formation of STIM1 puncta in PANC1, RAMA37, and HeLa cells. The sequence of events triggered by inhibition of ATP production included a rapid decline of ATP, depletion of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) and a slow calcium leak from the ER followed by formation of STIM1 puncta. STIM1 puncta induced by ATP depletion were co-localized with clusters of ORAI1 channels. STIM1-ORAI1 clusters that developed as a result of ATP depletion were very poor mediators of Ca(2+) influx. Re-translocation of STIM1 from puncta back to the ER was observed during total ATP depletion. We can therefore conclude that STIM1 translocation and re-translocation as well as formation of STIM1-ORAI1 clusters occur in an ATP-independent fashion and under conditions of PI(4,5)P(2) depletion.

Acute pancreatitis (AP), a human disease in which the pancreas digests itself, has substantial mortality with no specific therapy. The major causes of AP are alcohol abuse and gallstone complications, but it also occurs as an important side effect of the standard asparaginase-based therapy for childhood acute lymphoblastic leukemia. Previous investigations into the mechanisms underlying pancreatic acinar cell death induced by alcohol metabolites, bile acids, or asparaginase indicated that loss of intracellular ATP generation is an important factor. We now report that, in isolated mouse pancreatic acinar cells or cell clusters, removal of extracellular glucose had little effect on this ATP loss, suggesting that glucose metabolism was severely inhibited under these conditions. Surprisingly, we show that replacing glucose with galactose prevented or markedly reduced the loss of ATP and any subsequent necrosis. Addition of pyruvate had a similar protective effect. We also studied the effect of galactose in vivo in mouse models of AP induced either by a combination of fatty acids and ethanol or asparaginase. In both cases, galactose markedly reduced acinar necrosis and inflammation. Based on these data, we suggest that galactose feeding may be used to protect against AP., Introduction Acute pancreatitis (AP) is an inflammatory disease that originates in the exocrine pancreas, where inactive pancreatic proenzymes become prematurely activated inside the pancreatic acinar cells (PACs), digesting the pancreas [...]

Here we describe a technique that allows us to visualize in real time the formation and dynamics (fusion, changes of shape, and translocation) of vacuoles in living cells. The technique involves infusion of a dextran-bound fluorescent probe into the cytosol of the cell via a patch pipette, using the whole-cell patch-clamp configuration. Experiments were conducted on pancreatic acinar ceils stimulated with supramaximal concentrations of cholecystokinin (CCK). The vacuoles, forming in the cytoplasm of the cell, were revealed as dark imprints on a bright fluorescence background, produced by the probe and visualized by confocal microscopy. A combination of two dextran-bound probes, one infused into the cytosol and the second added to the extracellular solution, was used to identify endocytic and nonendocytic vacuoles. The cytosolic dextran-bound probe was also used together with a Golgi indicator to illustrate the possibility of combining the probes and identifying the localization of vacuoles with respect to other cellular organelles in pancreatic acinar cells. Combinations of cytosollc dextran-bound probes with endoplasmic reticulum (ER) or mitochondrial probes were also used to simultaneously visualize vacuoles and corresponding organelles. We expect that the new technique will also be applicable and useful for studies of vacuole dynamics in other cell types. pancreatic acinar cells; confocal microscopy; patch clamp; cholecystokinin

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. Interestingly, when caspase-9 activation was inhibited, activation of caspase-8 was increased. Half-maximum activation ([t.sub.0.5]) of caspase-9 occurred within ~2 min and was identified at or in close proximity to mitochondria, whereas [t.sub.0.5] for caspase-8 occurred within ~26 min of menadione application and was distributed homogeneously throughout cells. Caspase-9 but not caspase-8 activation was blocked completely by the calcium chelator BAPTA or bongkrekic acid, an inhibitor of the mitochondrial permeability transition pore. In contrast, caspase-8 but not caspase-9 activation was blocked by the destruction of lysosomes (preincubation with Gly-Phe [beta]-naphthylamide, a cathepsin C substrate), loss of lysosomal acidity (bafilomycin A1), or inhibition of cathepsin L or D. Using pepstatin A-BODIPY FL conjugate, we confirmed translocation of cathepsin D out of lysosomes in response to menadione. We conclude that the oxidative stressor menadione induces two independent apoptotic pathways within pancreatic acinar cells: the classical mitochondrial calcium-dependent pathway that is initiated rapidly in the majority of cells, and a slower, caspase-8-mediated pathway that depends on the lysosomal activities of cathepsins and is used when the caspase-9 pathway is disabled. pancreas; acinar cells; menadione doi:10.1152/ajpgi.00103.2007

Inositol triphosphate (IP3) and cyclic ADP-ribose (cADPr) evoke a marked decrease in the free calcium concentration inside zymogen granules (ZG) of pancreatic acinar cells. Using confocal microscopy, it has been shown that IP3 and cADPr induce the rapid release Ca2+ from the granules. A novel high resolution method further showed that IP3-mediated Ca2+ release causes a spike in cytosolic Ca2+ generation outside the ZG.

Microscopic studies using fluorescent probes of the release and uptake of Ca2+ from cell nuclei in liver show that the Ca2+-sensitive fluorescent probe Fura 2 localizes mainly to the nuclear envelope, indicating that the inward and outward transport of Ca2+ from the nuclear envelope is responsible for the inositol triphosphate-dependent secretion of Ca2+. Fluorescent Ca2+ indicator-tagged dextrans display a uniform distribution in the nucleoplasm, while variations in external Ca2+ alter the nucleoplasmic Ca2+ level. Ca2+ released from the nuclear envelope enters nucleoplasm and diffuses out through nuclear pore complexes.

This article discusses the role of calcium signaling and ATP production in pancreatic cancer. Pancreatic cancer is a significant health burden and has a low survival rate. Specific gene mutations, as well as risk factors such as aging, obesity, and inflammatory diseases, contribute to the development of pancreatic cancer. The study mentioned in the article investigates calcium signaling and ATP levels in pancreatic acinar cells from a genetic model of pancreatic cancer. The results suggest that aberrant calcium signaling and metabolic changes play a crucial role in pancreatic cancer progression. Further research in these areas could lead to the identification of new therapeutic targets for this deadly disease. [Extracted from the article]