ISSN:
1432-1912
Keywords:
Key words Calmodulin antagonistsr
;
Phosphoinositide turnover
;
Phospholipase C
;
C6-glioma cells
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract To investigate the role of calmodulin (CaM)-dependent pathways in agonist-induced phosphoinositide (PI) turnover, the influence of several CaM antagonists on PI-phospholipase C (PLC) activation in intact and permeabilized C6 glioma cells was examined. The extent of PI turnover was assessed by measuring the accumulation of inositol phosphates (IPs) in the presence of LiCl in C6 glioma cells prelabelled with myo-[3H]inositol. Trifluoperazine, N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W-7), fendiline and calmidazolium themselves had no effect on basal IP formation, but concentration-dependently (1–30 μM) potentiated ATP-, NaF- and A23187-stimulated IP formation. The maximal response to ATP (1 mM) was increased by up to 50%, while the concentration for half-maximal effect (EC50, 60 μM) was unaffected by trifluoperazine. In digitonin-permeabilized C6 glioma cells, the concentration-dependent increase of PI-PLC activation elicited by free Ca2+ was potentiated by the GTP analogue, guanosine 5′-[γ-thio]triphosphate (GTPγS), with an EC50 of 6 μM. Trifluoperazine (1–30 μM) enhanced the Ca2+-stimulated IP formation concentration dependently and this potentiation was counteracted by the addition of CaM. In the combined presence of each CaM antagonist studied and GTPγS, an additive increase in IP formation was observed. The results indicate that CaM antagonists enhance stimulus-induced IP formation in C6 glioma cells primarily by increasing the Ca2+-dependent activation of PI-PLC.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00171328
Permalink
