title: Mechanisms underlying the neuronal calcium sensor-1-evoked enhancement of exocytosis in PC12 cells.
abstract: Neuronal calcium sensor-1 (NCS-1) or the originally identified homologue frequenin belongs to a superfamily of EF-hand calcium binding proteins. Although NCS-1 is thought to enhance synaptic efficacy or exocytosis mainly by activating ion channel function, the detailed molecular basis for the enhancement is still a matter of debate. Here, mechanisms underlying the NCS-1-evoked enhancement of exocytosis were investigated using PC12 cells overexpressing NCS-1. NCS-1 was found to have a broad distribution in the cells being partially distributed in the cytosol and associated to vesicles and tubular-like structures. Biochemical and immunohistochemical studies indicated that NCS-1 partially colocalized with the light synaptic vesicle marker synaptophysin. When stimulated with UTP or bradykinin, agonists to phospholipase C-linked receptors, NCS-1 enhanced the agonist-mediated elementary and global Ca2+ signaling and increased the levels of downstream signals of phosphatidylinositol 4-kinase. NCS-1 enhanced the UTP-evoked exocytosis but not the depolarization-evoked Ca2+ responses or exocytosis, suggesting that the enhancement by NCS-1 should involve phospholipase C-linked receptor-mediated signals rather than the Ca2+ channels or exocytotic machinery per se. Taken together, NCS-1 enhances phosphoinositide turnover, resulting in enhancement of Ca2+ signaling and exocytosis. This is a novel regulatory mechanism of exocytosis that might involve the activation of phosphatidylinositol 4-kinase.
authors.affiliation: Section of Neuropharmacology, Division of Pharmacology, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan. skoizumi@nihs.go.jp
authors.forename: Schuichi
authors.initials: S
authors.lastname: Koizumi
authors.forename: Patrizia
authors.initials: P
authors.lastname: Rosa
authors.forename: Gary B
authors.initials: GB
authors.lastname: Willars
authors.forename: R A John
authors.initials: RA
authors.lastname: Challiss
authors.forename: Elena
authors.initials: E
authors.lastname: Taverna
authors.forename: Maura
authors.initials: M
authors.lastname: Francolini
authors.forename: Martin D
authors.initials: MD
authors.lastname: Bootman
authors.forename: Peter
authors.initials: P
authors.lastname: Lipp
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Inoue
authors.forename: John
authors.initials: J
authors.lastname: Roder
authors.forename: Andreas
authors.initials: A
authors.lastname: Jeromin
mesh_terms: D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D005089:Exocytosis / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides / Q000378:metabolism / Q000502:physiology*; D016716:PC12 Cells; D010716:Phosphatidylinositols / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000378:metabolism; D014544:Uridine Triphosphate / Q000494:pharmacology
chemical_list: D002135:Calcium-Binding Proteins; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides; D010716:Phosphatidylinositols; C101464:frequenin calcium sensor proteins; D011188:Potassium; D001920:Bradykinin; D002118:Calcium; D014544:Uridine Triphosphate