Release currents of IP(3) receptor channel clusters and concentration profiles

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Item Type:	Article
Title:	Release currents of IP(3) receptor channel clusters and concentration profiles
Creators Name:	Thul, R. and Falcke, M.
Abstract:	We simulate currents and concentration profiles generated by Ca(2+) release from the endoplasmic reticulum (ER) to the cytosol through IP(3) receptor channel clusters. Clusters are described as conducting pores in the lumenal membrane with a diameter from 6 nm to 36 nm. The endoplasmic reticulum is modeled as a disc with a radius of 1-12 microm and an inner height of 28 nm. We adapt the dependence of the currents on the trans Ca(2+) concentration (intralumenal) measured in lipid bilayer experiments to the cellular geometry. Simulated currents are compared with signal mass measurements in Xenopus oocytes. We find that release currents depend linearly on the concentration of free Ca(2+) in the lumen. The release current is approximately proportional to the square root of the number of open channels in a cluster. Cytosolic concentrations at the location of the cluster range from 25 microM to 170 microM. Concentration increase due to puffs in a distance of a few micrometers from the puff site is found to be in the nanomolar range. Release currents decay biexponentially with timescales of <1 s and a few seconds. Concentration profiles decay with timescales of 0.125-0.250 s upon termination of release.
Keywords:	Biophysics, Calcium, Calcium Channels, Cytosol, Drug Dose-Response Relationship, Endoplasmic Reticulum, Inositol 1,4,5-Trisphosphate Receptors, Intracellular Membranes, Lipid Bilayers, Theoretical Models, Cytoplasmic and Nuclear Receptors, Time Factors, Animals
Source:	Biophysical Journal
ISSN:	0006-3495
Publisher:	Biophysical Society
Volume:	86
Number:	5
Page Range:	2660-2673
Date:	May 2004
Official Publication:	https://doi.org/10.1016/S0006-3495(04)74322-2
PubMed:	View item in PubMed

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