title: Alterations in exocytosis induced by neuronal Ca2+ sensor-1 in bovine chromaffin cells.
abstract: A variety of Ca2+ binding proteins are known to play an integral role in catecholamine release from synapses as well as secretory cells, such as chromaffin cells. The Drosophila protein frequenin and its mammalian homolog neuronal Ca2+ sensor-1 (NCS-1) belong to a family of Ca2+ sensors with EF hands that bind Ca2+ and then interact with other proteins. Frequenin/NCS-1 has been shown to enhance exocytotic activity in addition to altering Ca2+ channel regulation. To better understand how NCS-1 regulates stimulus-secretion coupling, bovine chromaffin cells were infected with Semliki Forest virus (SFV) vectors containing the rat NCS-1 gene. Cells were studied in the perforated whole-cell patch-clamp configuration. Membrane capacitance was monitored as an indicator of exocytosis-endocytosis. Exocytosis elicited by membrane depolarization was not significantly different between cells infected with SFV expressing green fluorescent protein (GFP) or GFP plus NCS-1, except that the overexpression of NCS-1 resulted in a faster rundown in exocytosis. When cells were stimulated with histamine, NCS-1 overexpression led to higher exocytosis, as well as [Ca2+]i elevation. Immunocytochemistry showed a similar distribution of NCS-1 and phosphatidylinositol 4-kinase beta (PI4Kbeta). NCS-1 and PI4Kbeta coimmunoprecipitate, opening up the possibility that the two proteins directly interact. These results suggest that NCS-1 may regulate cellular activity through the modulation of the phosphatidylinositol signaling pathway.
authors.affiliation: Department of Neurobiology, Pharmacology, and Physiology, The University of Chicago, Chicago, Illinois 60637, USA. cypan@drugs.bsd.uchicago.edu
authors.forename: Chien-Yuan
authors.initials: CY
authors.lastname: Pan
authors.forename: Andreas
authors.initials: A
authors.lastname: Jeromin
authors.forename: Kenneth
authors.initials: K
authors.lastname: Lundstrom
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Yoo
authors.forename: John
authors.initials: J
authors.lastname: Roder
authors.forename: Aaron P
authors.initials: AP
authors.lastname: Fox
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D002417:Cattle; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D025802:Electric Capacitance; D004558:Electric Stimulation; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D005822:Genetic Vectors / Q000235:genetics / Q000378:metabolism; D006632:Histamine / Q000378:metabolism / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D012672:Semliki forest virus / Q000235:genetics; D012964:Sodium / Q000378:metabolism; D014162:Transfection
chemical_list: D002135:Calcium-Binding Proteins; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides; C101464:frequenin calcium sensor proteins; D006632:Histamine; D012964:Sodium; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D002118:Calcium