Role of elementary Ca2+ puffs in generating repetitive Ca2+ oscillations

• Published in: The EMBO journal 2001-01, Vol.20 (1-2), p.65-76
• Main Authors: Marchant, Jonathan S., Parker, Ian
• Format: Article
• Language: English
• Subjects: Ca2+ oscillation; Ca2+ puffs; Ca2+ waves; inositol trisphosphate; Wave propagation; Xenopus oocyte
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1093/emboj/20.1.65

Inositol (1,4,5)‐trisphosphate (IP 3 ) liberates intracellular Ca 2+ both as localized ‘puffs’ and as repetitive waves that encode information in a frequency‐dependent manner. Using video‐rate confocal imaging, together with photorelease of IP 3 in Xenopus oocytes, we investigated the roles of puffs in determining the periodicity of global Ca 2+ waves. Wave frequency is not delimited solely by cyclical recovery of the cell's ability to support wave propagation, but further involves sensitization of Ca 2+ ‐induced Ca 2+ release by progressive increases in puff frequency and amplitude at numerous sites during the interwave period, and accumulation of pacemaker Ca 2+ , allowing a puff at a ’focal‘ site to trigger a subsequent wave. These specific ’focal' sites, distinguished by their higher sensitivity to IP 3 and close apposition to neighboring puff sites, preferentially entrain both the temporal frequency and spatial directionality of Ca 2+ waves. Although summation of activity from many stochastic puff sites promotes the generation of regularly periodic global Ca 2+ signals, the properties of individual Ca 2+ puffs control the kinetics of Ca 2+ spiking and the (higher) frequency of subcellular spikes in their local microdomain.