Biophysical re-equilibration of Ca2+ fluxes as a simple biologically plausible explanation for complex intracellular Ca2+ release patterns.
Physiological regulation of Ca(2+) release from the endoplasmic reticulum (ER) is critical for cell function. Recent direct measurements of free [Ca(2+)] inside the ER ([Ca(2+)](ER)) revealed that [Ca(2+)](ER) itself is a key regulator of ER Ca(2+) handling. However, the role of this new regulatory process in generating various patterns of Ca(2+) release remains to be elucidated in detail. Here, we incorporate the recently quantified experimental correlations between [Ca(2+)](ER) and Ca(2+) movements across the ER membrane into a mathematical model ER Ca(2+) handling. The model reproduces basic experimental dynamics of [Ca(2+)](ER). Although this was not goal in model design, the model also exhibits mechanistically unclear experimental phenomena such as "quantal" Ca(2+) release, and "store charging" by increasing resting cytosolic [Ca(2+)]. While more complex explanations cannot be ruled out, on the basis of our data we propose that "quantal release" and "store charging" could be simple re-equilibration phenomena, predicted by the recently quantified biophysical dynamics of Ca(2+) movements across the ER membrane.
Burdakov
Denis
D
Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK. denis.burdakov@manchester.ac.uk
Verkhratsky
Alexei
A
D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D004563:Electrochemistry; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D008433:Mathematics; D008962:Models, Theoretical
D002118:Calcium