title: Cytosolic [Ca2+] regulation of InsP3-evoked puffs.
abstract: InsP3-mediated puffs are fundamental building blocks of cellular Ca2+ signalling, and arise through the concerted opening of clustered InsP3Rs (InsP3 receptors) co-ordinated via Ca2+-induced Ca2+ release. Although the Ca2+ dependency of InsP3Rs has been extensively studied at the single channel level, little is known as to how changes in basal cytosolic [Ca2+] would alter the dynamics of InsP3-evoked Ca2+ signals in intact cells. To explore this question, we expressed Ca2+-permeable channels (nicotinic acetylcholine receptors) in the plasma membrane of voltage-clamped Xenopus oocytes to regulate cytosolic [Ca2+] by changing the electrochemical gradient for extracellular Ca2+ entry, and imaged Ca2+ liberation evoked by photolysis of caged InsP3. Elevation of basal cytosolic [Ca2+] strongly increased the amplitude and shortened the latency of global Ca2+ waves. In oocytes loaded with EGTA to localize Ca2+ signals, the number of sites at which puffs were observed and the frequency and latency of puffs were strongly dependent on cytosolic [Ca2+], whereas puff amplitudes were only weakly affected. The results of the present study indicate that basal cytosolic [Ca2+] strongly affects the triggering of puffs, but has less of an effect on puffs once they have been initiated.
authors.affiliation: Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, U.S.A. michiko.yamasaki-mann@dpag.ox.ac.uk
authors.forename: Michiko
authors.initials: M
authors.lastname: Yamasaki-Mann
authors.forename: Angelo
authors.initials: A
authors.lastname: Demuro
authors.forename: Ian
authors.initials: I
authors.lastname: Parker
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D003600:Cytosol / Q000502:physiology*; D005260:Female; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000502:physiology*; D010782:Photolysis; D014982:Xenopus laevis
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; D002118:Calcium