Juris Galvanovskis and Bo Söderberg The Probability of Exocytosis: The Dependence on
Ca^{2+} Sensing Latency Times, Ca^{2+}
Channel Kinetic Parameters and
ClusteringAbstract:The release of secrete from secretory vesicles and granules requires a transient increase of intracellular Ca ^{2+} concentration in the vicinity of the fusion
site. Usually there is a short delay to the onset of the
actual fusion of membranes, that is described as a latency
time of the Ca^{2+} sensing system of the secreting
machinery. The delay time affects in an essential way the
probability for a certain granule to fuse with the
plasmalemma and to release its contents into the
extra-cellular space. We have investigated here,
theoretically and numerically, the extent of this influence
and its dependence on the parameters of Ca^{2+}
channels, channel clustering, the Ca^{2+} sensing
system, and the length of depolarizing pulses. We used a
linear probabilistic model for a random opening and closing
of channels, that yields an explicit expression for the
Laplace transforms of the waiting time distributions for at
least one channel to be open during the latency time. This
allows one in principle to calculate the probability that a
vesicle will fuse with plasmalemma during the action
potential. We used the theoretical results to test our
numerical simulations.LU TP 01-18 |