The Ca2+ stores of Dictyostelium discoideum amoebae take part in control of homoeostasis of the cytosolic free Ca2+ concentration ([Ca2+]i) and the cyclic-AMP-induced [Ca2+]i-signalling cascade. In order to characterize regulatory mechanisms of these stores, we incubated cells with the calmodulin antagonist calmidazolium. Measurement of permeabilized and intact cells in suspension with a Ca2+-sensitive electrode revealed that calmidazolium induced Ca2+ release from intracellular stores, influx of Ca2+ across the plasma membrane and subsequent efflux. In single fura-2-loaded cells calmidazolium evoked rapid and global transient elevations of [Ca2+]i. Other calmodulin antagonists (trifluoperazine, chlorpromazine, fendiline and W7) also induced transient elevations of [Ca2+]i, which were, however, slower and observed in fewer cells. The calmidazolium-induced influx of extracellular Ca2+ was inhibited by preincubation with 2,5-di-(t-butyl)-1,4-hydroquinone (BHQ) and 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl), both known to interact with pumps of the inositol 1,4,5-trisphosphate (IP3)-sensitive store, and by the V-type H+-ATPase inhibitor bafilomycin A1, which affects the acidosomal Ca2+ store. Incubation with pump inhibitors did not itself induce changes in [Ca2+]i. We conclude that the effects of calmidazolium are, at least in part, mediated by its calmodulin-antagonizing properties, that it acts by inducing Ca2+ release from filled storage compartments, and that its target of action is both the IP3-sensitive store and the acidosome; emptying of these stores leads to influx of extracellular Ca2+.
Skip Nav Destination
Follow us on Twitter @Biochem_Journal
Article navigation
January 1996
-
Cover Image
Cover Image
- PDF Icon PDF LinkTable of Contents
Research Article|
January 15 1996
Calmidazolium leads to an increase in the cytosolic Ca2+ concentration in Dictyostelium discoideum by induction of Ca2+ release from intracellular stores and influx of extracellular Ca2+ Available to Purchase
Christina SCHLATTERER;
Christina SCHLATTERER
*
*To whom correspondence should be addressed.
Search for other works by this author on:
Ralph SCHALOSKE
Ralph SCHALOSKE
1Fakultät für Biologie, PF 5560, Universität Konstanz, D-78434 Konstanz, Federal Republic of Germany
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
August 11 1995
Revision Received:
September 18 1995
Accepted:
September 19 1995
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1996
1996
Biochem J (1996) 313 (2): 661–667.
Article history
Received:
August 11 1995
Revision Received:
September 18 1995
Accepted:
September 19 1995
Citation
Christina SCHLATTERER, Ralph SCHALOSKE; Calmidazolium leads to an increase in the cytosolic Ca2+ concentration in Dictyostelium discoideum by induction of Ca2+ release from intracellular stores and influx of extracellular Ca2+. Biochem J 15 January 1996; 313 (2): 661–667. doi: https://doi.org/10.1042/bj3130661
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Biochemical Society Member Sign in
Sign InSign in via your Institution
Sign in via your InstitutionGet Access To This Article
Follow us on Twitter @Biochem_Journal
Open Access for all
We offer compliant routes for all authors from 2025. With library support, there will be no author nor reader charges in 5 journals. Check here |
![]() View past webinars > |