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

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Abstracts
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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 [[log in to unmask]]
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[End dictyNews, volume 39, number 1]