dictyNews Volume 22 Number 13

Published in

· 10 months ago

Dicty News 
Electronic Edition 
Volume 22, number 13 
May 28, 2004 

Please submit abstracts of your papers as soon as they have been 
accepted for publication by sending them to dicty@northwestern.edu 
or by using the form at 
http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. 

Back issues of Dicty-News, the Dicty Reference database and other  
useful information is available at dictyBase - http://dictybase.org. 

 

 
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  Abstracts 
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A link of Ca2+ to cAMP oscillations in Dictyostelium: the calmodulin 
antagonist W-7 potentiates cAMP relay and transiently inhibits the acidic 
Ca2+-store 

Dieter Malchow, Daniel F. Lusche and Christina Schlatterer  
Department of Biology, University of Konstanz, D-78457 Konstanz, Germany 

BMC Developmental Biology, in press 

 
Background: During early differentiation of Dictyostelium the attractant 
cAMP is released periodically to induce aggregation of the cells. Here we 
pursue the question whether pulsatile cAMP signaling is coupled to a basic 
Ca2+-oscillation.  
Results: We found that the calmodulin antagonist W-7 transiently enhanced 
cAMP spikes. We show that W-7 acts on an acidic Ca2+-store: it abolished 
ATP-dependent vesicular acidification, inhibited V-type H+ATPase activity 
more potently than the weaker antagonist W-5 and caused vesicular 
Ca2+-leakage. Concanamycin A, an inhibitor of the V-type H+-pump, blocked 
the Ca2+-leakage elicited by W-7 as well as cAMP-oscillations in the 
presence of W-7. Concanamycin A caused an increase of the cytosolic 
Ca2+-concentration whereas W-7 did not. In case of the latter, Ca2+ was 
secreted by the cells. In accord with our hypothesis that the link from  
Ca2+ to cAMP synthesis is mediated by a Ca2+-dependent phospholipase C we 
found that W-7 was not active in the phospholipase C knockout mutant.  
Conclusion: We conclude that the potentiation of cAMP relay by W-7 is due 
to a transient inhibition of the acidic Ca2+-store. The inhibition of the 
proton pump by W-7 causes a leakage of Ca2+ that indirectly stimulates 
adenylyl cyclase activity via phospholipase C.  

 
Submitted by: Christina Schlatterer [Christina.Schlatterer@uni-konstanz.de] 

 
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[End Dicty News, volume 22, number 13]