Membrane-initiated Ca(2+) signals are reshaped during propagation to subcellular regions.
An important aspect of Ca(2+) signaling is the ability of cells to generate intracellular Ca(2+) waves. In this study we have analyzed the cellular and subcellular kinetics of Ca(2+) waves in a neuroendocrine transducer cell, the melanotrope of Xenopus laevis, using the ratiometric Ca(2+) probe indo-1 and video-rate UV confocal laser-scanning microscopy. The purpose of the present study was to investigate how local Ca(2+) changes contribute to a global Ca(2+) signal; subsequently we quantified how a Ca(2+) wave is kinetically reshaped as it is propagated through the cell. The combined kinetics of all subcellular Ca(2+) signals determined the shape of the total cellular Ca(2+) signal, but each subcellular contribution to the cellular signal was not constant in time. Near the plasma membrane, [Ca(2+)](i) increased and decreased rapidly, processes that can be described by a linear and exponential function, respectively. In more central parts of the cell slower kinetics were observed that were best described by a Hill equation. This reshaping of the Ca(2+) wave was modeled with an equation derived from a low-pass RC filter. We propose that the differences in spatial kinetics of the Ca(2+) signal serves as a mechanism by which the same cellular Ca(2+) signal carries different regulatory information to different subcellular regions of the cell, thus evoking differential cellular responses.
Koopman
W J
WJ
Department of Cellular Animal Physiology, University of Nijmegen, Nijmegen, The Netherlands.
Scheenen
W J
WJ
Errington
R J
RJ
Willems
P H
PH
Bindels
R J
RJ
Roubos
E W
EW
Jenks
B G
BG
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002138:Calibration; D004563:Electrochemistry; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism*; D021621:Imaging, Three-Dimensional; D007424:Intracellular Fluid / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D014982:Xenopus laevis
D002118:Calcium