title: Neuronal calcium sensor-1 and phosphatidylinositol 4-kinase beta regulate IgE receptor-triggered exocytosis in cultured mast cells.
abstract: We examined the possible occurrence and function of neuronal Ca(2+) sensor 1 (NCS-1/frequenin) in the mast cell line rat basophilic leukemia, RBL-2H3. This protein has been implicated in the control of neurosecretion from dense core granules in neuronal cells as well as in the control of constitutive secretory pathways in both yeast and mammalian cells. We show that RBL-2H3 cells, secretory cells of the immune system, endogenously express the 22-kDa NCS-1 protein as well as an immune-related 50-kDa protein. Both proteins associate in vivo with phosphatidylinositol 4-kinase beta (PI4Kbeta) and colocalize with the enzyme in the Golgi region. We show further that overexpression of NCS-1 in RBL-2H3 cells stimulates the catalytic activity of PI4Kbeta, increases IgE receptor (FcepsilonRI)-triggered hydrolysis of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)), and stimulates FcepsilonRI-triggered, but not Ca(2+) ionophore-triggered, exocytosis. Conversely, expression of a kinase-dead mutant of PI4Kbeta reduces PI4Kbeta activity, decreases FcepsilonRI-stimulated phosphatidylinositol 4,5-bisphosphate hydrolysis, and blocks FcepsilonRI-triggered, but not Ca(2+) ionophore-triggered, exocytosis. Our results indicate that PI(4)P, produced by the Golgi-localized PI4Kbeta, is the rate-limiting factor in the synthesis of the pool of PI(4,5)P(2) that serves as substrate for the generation of lipid-derived second messengers in FcepsilonRI-triggered cells. We conclude that NCS-1 is involved in the control of regulated exocytosis in nonneural cells, where it contributes to stimulus-secretion coupling by interacting with PI4Kbeta and positive regulation of its activity.
authors: Department of Cell and Developmental Biology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors: Yaara
authors: Y
authors: Kapp-Barnea
authors: Semyon
authors: S
authors: Melnikov
authors: Irit
authors: I
authors: Shefler
authors: Andreas
authors: A
authors: Jeromin
authors: Ronit
authors: R
authors: Sagi-Eisenberg
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase / Q000235:genetics / Q000502:physiology*; D000818:Animals; D020013:Calcium Signaling / Q000235:genetics / Q000276:immunology*; D002135:Calcium-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000276:immunology; D005089:Exocytosis / Q000235:genetics / Q000276:immunology*; D008407:Mast Cells / Q000166:cytology / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017455:Receptors, IgE / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D014162:Transfection
chemical_list: D002135:Calcium-Binding Proteins; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides; D019269:Phosphatidylinositol 4,5-Diphosphate; D017455:Receptors, IgE; C101464:frequenin calcium sensor proteins; D019870:1-Phosphatidylinositol 4-Kinase