dictyNews Volume 35 Number 06

Published in

· 11 months ago

dictyNews 
Electronic Edition 
Volume 35, number 6 
September 3, 2010 

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

 
Differential regulation by phosphoinositides of bacterial uptake and Nramp1  
(Slc11a1)-induced resistance to Legionella infection in Dictyostelium  

Barbara Peracino, Alessandra Balest and Salvatore Bozzaro 
Department of Clinical and Biological Sciences, University of Turin,  
AOU S. Luigi, 10043 Orbassano (Torino), Italy 

 
J Cell Science, in press 

Membrane phosphatidylinositides recruit cytosolic proteins, regulating  
phagocytosis, macropinocytosis and endo-lysosomal vesicle maturation.  
Here we describe effects of PI3K, PTEN or PLC inactivation on Escherichia  
coli and Legionella pneumophila uptake by the professional phagocyte  
Dictyostelium discoideum. We show that L. pneumophila is engulfed by  
macropinocytosis, a process that is partially sensitive, unlike E. coli  
phagocytosis, to PI3K inactivation. Both processes are blocked by PLC i 
nhibition.  While E. coli is rapidly digested, Legionella proliferates  
intracellularly. Proliferation is blocked by constitutively expressing Nramp1,  
an endo-lysosomal iron transporter that confers resistance against invasive  
bacteria. Inactivating PI3K, but not PTEN or PLC, enhances Legionella 
infection and suppresses the protective effect of Nramp1 overexpression.  
PI3K activity is restricted to early infection and is not mediated by effects  
on the actin cytoskeleton, rather L. pneumophila, in contrast to E. coli,  
subverts phosphoinositide-sensitive fusion of Legionella-containing  
macropinosomes with acidic vesicles, without affecting Nramp1 recruitment.  
A model is presented to explain how Legionella escapes fusion with acidic  
vesicles and Nramp1-induced resistance to pathogens. 

 
Submitted by  Salvo Bozzaro [salvatore.bozzaro@unito.it] 
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[End dictyNews, volume 35, number 6]