Synaptotagmin regulates mast cell functions.
Synaptotagmin(s) (Syts), are products of a gene family implicated in the control of Ca2+-dependent exocytosis. Mast cells, specialized secretory cells that release mediators of inflammatory and allergic reactions in a process of regulated exocytosis, express Syt homologues and SNAREs (Soluble NSF Attachment proteins Receptors), which together with Syt constitute the core complex which mediates exocytotic vesicle docking and fusion. Rat basophilic leukemia cells (RBL-2H3), a tumor analogue of mucosal mast cells, express the Syt homologues Syt II, Syt III and Syt V Expression of Syt I, the neuronal Ca2+ sensor, in the RBL cells, resulted in its targeting to secretory granules and in prominent potentiation and acceleration of Ca2+-dependent exocytosis. Syt II is localized to an amine-free lysosomal compartment, which is also subjected to regulated exocytosis. Lysosomal exocytosis is negatively regulated by Syt II: overexpression of Syt II inhibited Ca2+-triggered exocytosis of lysosomes, while suppression of Syt II expression markedly potentiated this release. These findings implicate Syt homologues as key regulators of mast cell function.
Baram
D
D
Department of Cell Biology and Histology, Sackler School of Medicine, Tel Aviv University, Israel.
Mekori
Y A
YA
Sagi-Eisenberg
R
R
D000818:Animals; D020013:Calcium Signaling; D002135:Calcium-Binding Proteins; D003594:Cytoplasmic Granules / Q000378:metabolism; D005089:Exocytosis / Q000502:physiology*; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism*; D007476:Ionophores / Q000494:pharmacology; D015471:Leukemia, Basophilic, Acute / Q000473:pathology; D008247:Lysosomes / Q000378:metabolism; D008407:Mast Cells / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000502:physiology*; D008563:Membrane Lipids / Q000502:physiology; D008565:Membrane Proteins / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000502:physiology*; D010743:Phospholipids / Q000502:physiology; D050683:R-SNARE Proteins; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000502:physiology; D050600:SNARE Proteins; D050825:Synaptosomal-Associated Protein 25; D050857:Synaptotagmins; D014162:Transfection; D014407:Tumor Cells, Cultured; D033921:Vesicular Transport Proteins
D002135:Calcium-Binding Proteins; D018836:Inflammation Mediators; D007476:Ionophores; D008562:Membrane Glycoproteins; D008563:Membrane Lipids; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010743:Phospholipids; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins; C494208:SNAP25 protein, human; D050600:SNARE Proteins; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25; D033921:Vesicular Transport Proteins; D050857:Synaptotagmins