Buffer kinetics shape the spatiotemporal patterns of IP3-evoked Ca2+ signals

J Physiol. 2003 Dec 15;553(Pt 3):775-88. doi: 10.1113/jphysiol.2003.054247. Epub 2003 Oct 10.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Buffers
  • Calcium / physiology*
  • Calcium Channels / physiology*
  • Calcium Signaling / drug effects
  • Calcium Signaling / physiology*
  • Cytosol / physiology
  • Egtazic Acid / analogs & derivatives*
  • Egtazic Acid / pharmacology
  • Inositol 1,4,5-Trisphosphate / pharmacology*
  • Inositol 1,4,5-Trisphosphate Receptors
  • Kinetics
  • Microscopy, Confocal
  • Oocytes / cytology
  • Oocytes / drug effects
  • Oocytes / physiology*
  • Receptors, Cytoplasmic and Nuclear / physiology*
  • Xenopus Proteins / physiology
  • Xenopus laevis


  • Buffers
  • Calcium Channels
  • Inositol 1,4,5-Trisphosphate Receptors
  • Receptors, Cytoplasmic and Nuclear
  • Xenopus Proteins
  • Egtazic Acid
  • Inositol 1,4,5-Trisphosphate
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Calcium