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

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Abstracts
=========


The Dictyostelium discoideum RACK1 orthologue has roles in growth 
and development

Omosigho, N. N., Swaminathan, K., Plomann, M, Müller-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 Köln, Germany
Institute of Biochemistry II, Medical Faculty, University of Cologne, 
50931 Köln, Germany
Institute of Anatomy and Cell Biology, Ludwig-Maximilians-University, 
80336 München, 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 [[log in to unmask]]
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[End dictyNews, volume 40, number 15]