title: Cytosolic inositol 1,4,5-trisphosphate dynamics during intracellular calcium oscillations in living cells.
abstract: We developed genetically encoded fluorescent inositol 1,4,5-trisphosphate (IP3) sensors that do not severely interfere with intracellular Ca2+ dynamics and used them to monitor the spatiotemporal dynamics of both cytosolic IP3 and Ca2+ in single HeLa cells after stimulation of exogenously expressed metabotropic glutamate receptor 5a or endogenous histamine receptors. IP3 started to increase at a relatively constant rate before the pacemaker Ca2+ rise, and the subsequent abrupt Ca2+ rise was not accompanied by any acceleration in the rate of increase in IP3. Cytosolic [IP3] did not return to its basal level during the intervals between Ca2+ spikes, and IP3 gradually accumulated in the cytosol with a little or no fluctuations during cytosolic Ca2+ oscillations. These results indicate that the Ca2+ -induced regenerative IP3 production is not a driving force of the upstroke of Ca2+ spikes and that the apparent IP3 sensitivity for Ca2+ spike generation progressively decreases during Ca2+ oscillations.
authors.affiliation: Laboratory for Developmental Neurobiology, Brain Science Institute, RIKEN, Saitama 351-0198, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Matsu-ura
authors.forename: Takayuki
authors.initials: T
authors.lastname: Michikawa
authors.forename: Takafumi
authors.initials: T
authors.lastname: Inoue
authors.forename: Atsushi
authors.initials: A
authors.lastname: Miyawaki
authors.forename: Manabu
authors.initials: M
authors.lastname: Yoshida
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mikoshiba
mesh_terms: D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D011485:Protein Binding; D064529:Receptor, Metabotropic Glutamate 5; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011968:Receptors, Histamine / Q000378:metabolism; D018094:Receptors, Metabotropic Glutamate / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D015220:Calcium Channels; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D064529:Receptor, Metabotropic Glutamate 5; D018160:Receptors, Cytoplasmic and Nuclear; D011968:Receptors, Histamine; D018094:Receptors, Metabotropic Glutamate; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium