Role of voltage-dependent modulation of store Ca2+ release in synchronization of Ca2+ oscillations.
Slow waves are rhythmic depolarizations that underlie mechanical activity of many smooth muscles. Slow waves result through rhythmic Ca(2+) release from intracellular Ca(2+) stores through inositol 1,4,5-trisphosphate (IP(3)) sensitive receptors and Ca(2+)-induced Ca(2+) release. Ca(2+) oscillations are transformed into membrane depolarizations by generation of a Ca(2+)-activated inward current. Importantly, the store Ca(2+) oscillations that underlie slow waves are entrained across many cells over large distances. It has been shown that IP(3) receptor-mediated Ca(2+) release is enhanced by membrane depolarization. Previous studies have implicated diffusion of Ca(2+) or the second messenger IP(3) across gap junctions in synchronization of Ca(2+) oscillations. In this study, a novel mechanism of Ca(2+) store entrainment through depolarization-induced IP(3) receptor-mediated Ca(2+) release is investigated. This mechanism is significantly different from chemical coupling-based mechanisms, as membrane potential has a coupling effect over distances several orders of magnitude greater than either diffusion of Ca(2+) or IP(3) through gap junctions. It is shown that electrical coupling acting through voltage-dependent modulation of store Ca(2+) release is able to synchronize oscillations of cells even when cells are widely separated and have different intrinsic frequencies of oscillation.
Imtiaz
Mohammad S
MS
The Neuroscience Group, School of Biomedical Sciences, Faculty of Health, The University of Newcastle, Callaghan NSW 2308, Australia. Mohammad.Imtiaz@newcastle.edu.au
Katnik
Christopher P
CP
Smith
David W
DW
van Helden
Dirk F
DF
D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D003198:Computer Simulation; D003600:Cytosol / Q000378:metabolism; D017629:Gap Junctions; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008564:Membrane Potentials; D008954:Models, Biological; D015233:Models, Statistical; D008962:Models, Theoretical; D009130:Muscle, Smooth / Q000378:metabolism*; D009991:Oscillometry; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D015398:Signal Transduction; D012984:Software; D013997:Time Factors
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D002118:Calcium