Bridging Ral GTPase to Rho Pathways

doi:10.1074/jbc.270.38.22473

Bridging Ral GTPase to Rho Pathways

RLIP76, A Ral EFFECTOR WITH CDC42/Rac GTPase-ACTIVATING PROTEIN ACTIVITY (*)

From the (1) From U248, INSERM, Faculté de Médecine Lariboisière, 10 avenue de Verdun, 75010 Paris, U257 and
(2) U363, INSERM, Institut Cochin de Génétique Moléculaire, 75014 Paris, and
(3) U301, INSERM and SD 401 301, CNRS, Institut de Génétique Moléculaire, 75010 Paris, France

^§§ To whom correspondence should be addressed:
U248 INSERM, Faculté de Médecine Lariboisière, 10 avenue de Verdun, 75010 Paris, France
. Tel.: 33-1-44-89-77-58; Fax: 33-1-44-89-78-12; camonis{at}citi2.fr.

Abstract

RalA and RalB are GTPases of unknown function and are activated by proteins, RalGDS, that interact with the active form of another GTPase, Ras. To elucidate Ral function, we have searched for proteins interacting with an activated form of RalA using the two-hybrid method and a Jurkat cell library. We have identified a partial cDNA encoding a protein, RLIP1, which binds to activated RalA and this binding requires an intact effector domain of RalA. Biochemical data with purified RalA confirm the genetic results. This protein also bears a region of homology with GTPase-activating protein (GAP) domains that are involved in the regulation of GTPases of the Rho family and, indeed, RLIP1 displays a GAP activity acting upon Rac1 and CDC42, but not RhoA. This GAP region is not required for RLIP1 binding to Ral.

The whole cDNA was cloned, and it encodes a 76-kDa polypeptide, RLIP76, which also binds RalA. The Rho pathway is involved in membrane and cytoskeleton modifications after mitogenic stimulation and acts in parallel to and synergistically with the Ras pathway. We propose that these pathways are linked through a cascade composed of Ras RalGDS Ral RLIP76 CDC42/Rac1/Rho, allowing modulation of the Rho pathway by the Ras pathway.

Footnotes

↵^§ Recipient of a fellowship from Ministère de l'Education et de la Recherche Scientifique.
↵^¶ Recipient of a fellowship from ARC.
↵** An INSERM Visiting Scientist.
↵* This work was supported in part by grants from Association pour la Recherche contre le Cancer (ARC), Ligue Nationale contre le Cancer, Ligue contre le Cancer (Comitede Paris), and Groupement de Recherche et d'Etudes sur les Génomes. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) L42542[GenBank].
↵¹ The abbreviations used are:

GDS

guanine nucleotide dissociation stimulator

aa

amino acid(s)

GAP

GTPase-activating protein

MBP

maltose-binding protein

ORF

open reading frame

PCR

polymerase chain reaction

RACE

rapid amplification of cDNA ends

GST

glutathione S-transferase

PAGE

polyacrylamide gel electrophoresis

FISH

fluorescence in situ hybridization.
- Received June 28, 1995.
- Revision received July 31, 1995.