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EMBO J. 1996 Feb 15;15(4):810-6.

Ral-GTPases mediate a distinct downstream signaling pathway from Ras that facilitates cellular transformation.

Author information

1
Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.

Abstract

Ral proteins (RalA and RalB) comprise a distinct family of Ras-related GTPases (Feig and Emkey, 1993). Recently, Ral-GDS, the exchange factor that activates Ral proteins, has been shown to bind specifically to the activated forms of RasH, R-Ras and Rap1A, in the yeast two-hybrid system. Here we demonstrate that although all three GTPases have the capacity to bind Ral-GDS in mammalian cells, only RasH activates Ral-GDS. Furthermore, although constitutively activated Ra1A does not induce oncogenic transformation on its own, its expression enhances the transforming activities of both RasH and Raf. Finally, a dominant inhibitory form of RalA suppresses the transforming activities of both RasH and Raf. These results demonstrate that activation of Ral-GDS and thus its target, Ral, constitutes a distinct downstream signaling pathway from RasH that potentiates oncogenic transformation.

PMID:
8631302
PMCID:
PMC450279
[Indexed for MEDLINE]
Free PMC Article

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