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Originally published In Press as doi:10.1074/jbc.M105779200 on July 23, 2001
J. Biol. Chem., Vol. 276, Issue 38, 35909-35916, September 21, 2001
The Rac GTPase-activating Protein RotundRacGAP Interferes with
Drac1 and Dcdc42 Signalling in Drosophila melanogaster*
Karine
Raymond ,
Evelyne
Bergeret ,
Marie-Claire
Dagher ,
Rock
Breton§¶,
Ruth
Griffin-Shea , and
Marie-Odile
Fauvarque
From the Département de Biologie
Moléculaire et Structurale, CEA-CNRS-UJF, UMR 5092, 17 rue des
Martyrs, Grenoble 38054, and the § Institut de Biologie
Structurale CEA-CNRS-UJF, UMR 5075, 41 rue J. Horowitz,
Grenoble 38054, France
RhoGTPases are negatively regulated by
GTPase-activating proteins (GAPs). Here we demonstrate that
Drosophila RotundRacGAP is active in vitro on
Drac1 and Dcdc42 but not Drho1. Similarly, in yeast, RotundRacGAP
interacts specifically with Drac1 and Dcdc42, as well as with their
activated V12 forms, showing a particularly strong interaction with
Dcdc42V12. In the fly, lowering RotundRacGAP dosage specifically
modifies eye defects induced by expressing Drac1 or Dcdc42 but not
Drho1, confirming that Drac1 and Dcdc42 are indeed in vivo
targets of RotundRacGAP. Furthermore, embryonic-directed expression of
either RotundRacGAP, or dominant negative Drac1N17, transgenes induces
similar defects in dorsal closure and inhibits Drac1-dependent cytoskeleton assembly at the leading edge.
Expression of truncated forms of RotundRacGAP shows that the GAP domain
of RotundRacGAP is essential for its function. Unexpectedly, transgenes encoding Drac1N17, Dcdc42N17, or RotundRacGAP do not affect the c-Jun N-terminal kinase-dependent gene expression of
decapentaplegic and puckered, indicating that
another Drac1-independent signal redundantly activates this pathway.
Finally, in a situation where Drac1 is constitutively activated,
RotundRacGAP greatly reduces the ectopic expression of
decapentaplegic, possibly by negatively regulating Dcdc42.
*
This work was supported by the "Association pour la
Recherche contre le Cancer" (grant ARC 9392) and by the
Ministère de la Recherche et de l'Enseignement (grant ACCSV-4
and fellowship to K. R.).The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
¶
Present address: Dépt. d'Anatomie-Université
Laval, 2705 Laurier Blvd., Québec G1K 7P4, Canada.
To whom correspondence should be addressed: Tel.:
33-4-38-78-30-90; Fax: 33-4-38-78-44-99; E-mail:
mofauvarque@cea.fr.
Copyright © 2001 by The American Society for Biochemistry and Molecular Biology, Inc.

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