dictyNews Volume 39 Number 01

Published in

· 1 year ago

dictyNews 
Electronic Edition 
Volume 39, number 1 
January 11, 2013 

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========= 
Abstracts 
========= 

 
A dual role model for active Rac1 in cell migration 

Jan Faix and Igor Weber 

1 Hannover Medical School, Institute for Biophysical Chemistry,  
Carl-Neuberg-Str. 1, D-30623 Hannover, Germany  
2 Ruder Boskovic Institute, Division of Molecular Biology,  
Bijenicka 54, HR-10000 Zagreb, Croatia 

 
Small GTPases, in press 

Over time we have come to appreciate that the complex regulation  
of Rho GTPases involves additional mechanisms beyond the activating  
role of RhoGEFs, the inactivating function of RhoGAPs, and the  
sequestering activity of RhoGDIs. One class of regulatory mechanisms  
includes direct modifications of Rho proteins such as isoprenylation,  
phosphorylation, and SUMOylation. Rho GTPases can also regulate  
each other by means of crosstalk signaling, which is again mostly  
mediated by GEFs, GAPs, and GDIs. More complex mutual regulation  
ensues when and where two or more Rho proteins activate a common  
molecular target, i.e. share a common effector. We have recently  
unraveled a reciprocal mechanism wherein spatiotemporal dynamics of  
Rac1 activity during migration of Dictyostelium cells is apparently  
regulated by antagonizing interactions of Rac1-GTP with two distinct  
effectors. By monitoring specific fluorescent probes, activated Rac1 is  
simultaneously present at the leading edge, where it participates in  
Scar/WAVE-mediated actin polymerization, and at the trailing edge,  
where it induces formation of a DGAP1/cortexillin actin-bundling complex.  
Strikingly, in addition to their opposed localization, the two populations of  
activated Rac1 also display opposite kinetics of recruitment to the plasma  
membrane upon stimulation by chemoattractants. These findings with  
respect to Rac1 in Dictyostelium suggest a novel principle for regulation  
of Rho GTPase activity that might also play a role in other cell types and  
for other Rho family members. 
  
  
Submitted by Igor Weber [iweber@irb.hr] 
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[End dictyNews, volume 39, number 1]