Bridging Ral GTPase to Rho pathways. RLIP76, a Ral effector with CDC42/Rac GTPase-activating protein activity.
Ra1A and Ra1B are GTPases of unknown function and are activated by proteins, Ra1GDS, 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 Ra1A using the two-hybrid method and a Jurkat cell library. We have identified a partial cDNA encoding a protein, RLIP1, which binds to activated Ra1A and this binding requires an intact effector domain of Ra1A. Biochemical data with purified Ra1A 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 Ra1. 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 --> Ra1GDS --> Ra1 --> RLIP76 --> CDC42/Rac1/Rho, allowing modulation of the Rho pathway by the Ras pathway.
Jullien-Flores
V
V
U248, INSERM, Faculté de Médecine Lariboisière, Paris, France.
Dorseuil
O
O
Romero
F
F
Letourneur
F
F
Saragosti
S
S
Berger
R
R
Tavitian
A
A
Gacon
G
G
Camonis
J H
JH
D018528:ATP-Binding Cassette Transporters; D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D016384:Consensus Sequence; D017931:DNA Primers / Q000737:chemistry; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D020725:ral GTP-Binding Proteins; D020703:ras GTPase-Activating Proteins; D020741:rho GTP-Binding Proteins
D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D017931:DNA Primers; D020690:GTPase-Activating Proteins; D011506:Proteins; C095637:RALBP1 protein, human; D020703:ras GTPase-Activating Proteins; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D020725:ral GTP-Binding Proteins; D020741:rho GTP-Binding Proteins