dictyNews Volume 40 Number 15

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dictyNews 
Electronic Edition 
Volume 40, number 15 
June 20, 2014 

Please submit abstracts of your papers as soon as they have been 
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========= 
Abstracts 
========= 

 
The Dictyostelium discoideum RACK1 orthologue has roles in growth  
and development 

Omosigho, N. N., Swaminathan, K., Plomann, M, MŸller-Taubenberger,  
A., Noegel, A. A., Riyahi, T. Y.  

Institute of Biochemistry I, Medical Faculty, Center for Molecular Medicine  
Cologne (CMMC) and Cologne Excellence Cluster on Cellular Stress  
Responses in Aging-Associated Diseases (CECAD), University of Cologne,  
50931 Kšln, Germany 
Institute of Biochemistry II, Medical Faculty, University of Cologne,  
50931 Kšln, Germany 
Institute of Anatomy and Cell Biology, Ludwig-Maximilians-University,  
80336 MŸnchen, Germany 

 
Cell Commun Signal, in press 

Background 
The receptor for activated C-kinase 1 (RACK1) is a conserved protein  
belonging to the WD40 repeat family of proteins. It folds into a beta  
propeller with seven blades which allow interactions with many proteins.  
Thus it can serve as a scaffolding protein and have roles in several  
cellular processes. 
Results 
We identified the product of the Dictyostelium discoideum gpbB gene as  
the Dictyostelium RACK1 homolog. The protein is mainly cytosolic but can  
also associate with cellular membranes. DdRACK1 binds to  
phosphoinositides (PIPs) in protein-lipid overlay and liposome-binding  
assays. The basis of this activity resides in a basic region located in the  
extended loop between blades 6 and 7 as revealed by mutational analysis.  
Similar to RACK1 proteins from other organisms DdRACK1 interacts with  
G protein subunits alpha, beta and gamma as shown by yeast two-hybrid,  
pulldown, and immunoprecipitation assays. Unlike the Saccharomyces  
cerevisiae and Cryptococcus neoformans RACK1 proteins it does not appear  
to take over G-beta function in D. discoideum as developmental and other  
defects were not rescued in G-beta null mutants overexpressing  
GFP-DdRACK1. Overexpression of GFP-tagged DdRACK1 and a mutant  
version (DdRACK1mut) which carried a charge-reversal mutation in the  
basic region in wild type cells led to changes during growth and development. 
Conclusion 
DdRACK1 interacts with heterotrimeric G proteins and can through these  
interactions impact on processes specifically regulated by these proteins. 

 
Submitted by Angelika Noegel [noegel@uni-koeln.de] 
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[End dictyNews, volume 40, number 15]