XB-ART-4571J Physiol December 15, 2003; 553 (Pt 3): 775-88.
Buffer kinetics shape the spatiotemporal patterns of IP3-evoked Ca2+ signals.
Ca2+ liberation through inositol 1,4,5-trisphosphate receptors (IP3Rs) plays a universal role in cell regulation, and specificity of cell signalling is achieved through the spatiotemporal patterning of Ca2+ signals. IP3Rs display Ca2+-induced Ca2+ release (CICR), but are grouped in clusters so that regenerative Ca2+ signals may remain localized to individual clusters, or propagate globally between clusters by successive cycles of Ca2+ diffusion and CICR. We used confocal microscopy and photoreleased IP3 in Xenopus oocytes to study how these properties are modulated by mobile cytosolic Ca2+ buffers. EGTA (a buffer with slow ''on-rate'') speeded Ca2+ signals and ''balkanized'' Ca2+ waves by dissociating them into local signals. In contrast, BAPTA (a fast buffer with similar affinity) slowed Ca2+ responses and promoted ''globalization'' of spatially uniform Ca2+ signals. These actions are likely to arise through differential effects on Ca2+ feedback within and between IP3R clusters, because Ca2+ signals evoked by influx through voltage-gated channels were little affected. We propose that cell-specific expression of Ca2+-binding proteins with distinct kinetics may shape the time course and spatial distribution of IP3-evoked Ca2+ signals for specific physiological roles.
PubMed ID: 14555715
PMC ID: PMC2343635
Article link: J Physiol
Genes referenced: itpr1
References [+] :
Allbritton, Range of messenger action of calcium ion and inositol 1,4,5-trisphosphate. 1993, Pubmed, Xenbase