Decoding the words of calcium signals

LUCÍA FERNANDA LOPEZ; SILVINA PONCE DAWSON

Washington DC

Conferencia; iPoLS Annual Meeting; 2015

iPoLS

he role of cytosolic \ca\ on the kinetics of Inositol 1,4,5-triphosphate receptors (IP$_3$Rs) and on the dynamics of IP$_3$R-mediated \ca\ signals has been studied at large both experimentally and by modeling. The role of luminal calcium has not been investigated with that much detail although it has been found that it is relevant for signal termination in the case of \ca\ release through ryanodine receptors. In this work we present the results of observing the dynamics of luminal and cytosolic \ca\ simultaneously in {\it Xenopus Laevis} oocytes. Combining observations and modeling we conclude that there is a rapid mechanism that guarantees the availability of free \ca\ in the lumen even when a relatively large \ca\ release is evoked. Comparing the dynamics of depletion and re-uptake we estimate that they are consistent with a 80\% of luminal \ca being buffered. The rapid availability of free luminal \ca\ correlates with the observation that the lumen occupies a considerable volume in several regions across the images.