dictyNews Volume 27 Number 03

eZine lover (@eZine)

Published in 

Dicty News

 · 11 months ago

dictyNews 
Electronic Edition 
Volume 27, number 3 
August 4, 2006 

Please submit abstracts of your papers as soon as they have been 
accepted for publication by sending them to dicty@northwestern.edu 
or by using the form at 
http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. 

Back issues of dictyNews, the Dicty Reference database and other  
useful information is available at dictyBase - http://dictybase.org. 

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

 

Delineation of the roles played by RasG and RasC in cAMP-dependent signal  
transduction during the early development of Dictyostelium discoideum 

Parvin Bolourani, George B. Spiegelman and Gerald Weeks 

Department of Microbiology and Immunology, University of British Columbia 
Vancouver, BC, V6T 1Z3, Canada 

Corresponding author:  Gerald Weeks 
email: gerwee@interchange.ubc.ca 
Tel:  604-822-6649 
Fax:  604-822-6041 

Mailing address:   
Life Sciences Centre, 2350 Health Sciences Mall, University of British  
Columbia 
Vancouver, BC, V6T 1Z3, Canada 

 
Molecular Biology of the Cell, in press 

Upon starvation, the cellular slime mold Dictyostelium discoideum initiates  
a program of development leading to formation of multicellular structures.   
The initial cell aggregation requires chemotaxis to cyclic AMP (cAMP) and  
relay of the cAMP signal by the activation of adenylyl cyclase (ACA), and it  
has been shown previously that the Ras protein RasC is involved in both  
processes.  Insertional inactivation of the rasG gene resulted in delayed  
aggregation and a partial inhibition of early gene expression, suggesting  
that RasG also has a role in early development.  Both chemotaxis and ACA  
activation were reduced in the rasG- cells, but the effect on chemotaxis was  
more pronounced.  When the responses of rasG- cells to cAMP were compared  
with the responses of rasC- and rasC- rasG- strains, generated in otherwise  
isogenic backgrounds, these studies revealed that signal transduction through  
RasG is more important in chemotaxis and early gene expression, but that  
signal transduction through RasC is more important in ACA activation.  Since  
the loss of either of the two Ras proteins alone did not result in a total  
loss of signal output down either of the branches of the cAMP signal-response  
pathway, there appears to be some overlap of function.  

 
Submitted by: Gerry Weeks [gerwee@interchange.ubc.ca] 
----------------------------------------------------------------------------- 

 
WASP-Interacting Protein (WIPa) is Important for Actin Filament Elongation  
and Prompt Pseudopod Formation in Response to a Dynamic Chemoattractant  
Gradient 

Scott A. Myers, Laura R. Leper, and Chang Y. Chung 

Department of Pharmacology, Vanderbilt University Medical Center, Nashville,  
TN 37069 

 
Molecular Biology of the Cell, In Press 

The role of WASP-interacting protein (WIP) in the process of F-actin assembly  
during chemotaxis of Dictyostelium was examined.  Mutations of the WH1 domain  
of WASP led to a reduction in binding to WIPa, a newly identified homolog of  
mammalian WIP, a reduction of F-actin polymerization at the leading edge, and  
a reduction in chemotactic efficiency.  WIPa localizes to sites of new  
pseudopod protrusion and colocalizes with WASP at the leading edge.  WIPa  
increases actin elongation in vivo and in vitro in a WASP-dependent manner.  
WIPa overexpressing cells exhibit multiple microspike formation and defects  
in chemotactic efficiency due to frequent changes of direction.  WIPa  
translocates to the cortical membrane upon uniform cAMP stimulation.  This  
translocation appears to be dependent upon cortical F-actin assembly.   
Reduced expression of WIPa by expressing a hairpin WIPa (hp WIPa) construct  
resulted in more polarized cells that exhibit a delayed response to a new  
chemoattractant source due to delayed extension of pseudopod toward the new  
gradient.  These results suggest that WIPa is important for actin filament  
elongation required for new pseudopod protrusion and prompt reorientation of  
cells toward a new gradient by initiating localized bursts of actin  
polymerization and/or elongation. 

 
Submitted by: Chang Chung [chang.chung@vanderbilt.edu] 
============================================================================== 
[End dictyNews, volume 27, number 3]