<i>Saccharomyces cerevisiae</i> CDC25 [1028–1589] is a guanine nucleotide exchange factor for mammalian ras proteins and is ongenic in HIH3T3 cells

Chevallier-Multon, M C; Schweighoffer, Fabien; Barlat, Isabelle; Baudouy, Nicole; Fath, I; Duchesne, Marc; Tocqué, Bruno

doi:10.1016/0248-4900(92)90288-c

Cited by 7 publications

(11 citation statements)

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“…The last 23 aa of Ras have been shown to be dispensable for binding, in agreement with the results reported here for the Rab3a-Mss4 interaction (24,25). However, a mutational analysis of Ras has shown that the switch II domain (which consists of L4/␣2), but not the switch I domain, is important for binding to its GEFs (26 -28).…”

Section: Discussionsupporting

confidence: 78%

An Evolutionarily Conserved Domain in a Subfamily of Rabs Is Crucial for the Interaction with the Guanyl Nucleotide Exchange Factor Mss4

Burton

Slepnev

Camilli

1997

Journal of Biological Chemistry

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(1994) EMBO J. 13, 5547-5558). In order to identify the domain(s) of the GTPase that is important for this interaction, protein chimeras were constructed between Rab3a, which binds Mss4, and Rab5a, which does not bind Mss4. We have identified the amino-terminal portion of Rab3a as the Mss4-binding region, with the effector domain being critically required for binding and the flanking regions further enhancing the interaction. Sequence comparisons have revealed that Mss4-binding Rabs share more homology with each other than with Rabs that do not bind Mss4. The region of highest homology between these Rabs, which defines them as members of the same evolutionary branch within the Rab subfamily, coincides with the domain shown here to be critical for Mss4 binding. A mutation in the zincbinding domain of Mss4 (Mss4 D96H), a region that is highly conserved between Mss4 and its yeast homologue Dss4, completely abolished its property to bind to, and promote GDP-GTP exchange on, Rab3a. Thus, the preservation of the Mss4/Dss4-GTPase interaction appears to have been a critical factor in the evolution of this subset of Rab proteins.

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Section: Discussionsupporting

confidence: 78%

An Evolutionarily Conserved Domain in a Subfamily of Rabs Is Crucial for the Interaction with the Guanyl Nucleotide Exchange Factor Mss4

Burton

Slepnev

Camilli

1997

Journal of Biological Chemistry

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“…3). To further characterize the consequences of membrane targeting for Ras GEF function, 'we evaluated the (24) and others (28) have shown that Ras GEFs can stimulate the activity of normal Ras to activate transcription from RREs. While transfection of 1 ug of pZIP-cCDC25 DNA caused limited stimulation of transcription activation from pB4X-CAT (Fig.…”

Section: Resultsmentioning

confidence: 99%

Membrane-targeting potentiates guanine nucleotide exchange factor CDC25 and SOS1 activation of Ras transforming activity.

Quilliam

Huff

Rabun

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

124

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Growth factor-triggered activation of Ras proteins is believed to be mediated by guanine nucleotide exchange factors (CDC25/GRF and SOS1/2) that promote formation of the active Ras GTP-bound state. Although the mechaism(s) of guanine nucleotide exchange factor regulation is unclear, recent studies suggest that translocation of SOS1 to the plasma membrane, where Ras is located, might be responsible for Ras activation. To evaluate this model, we generated constructs that encode the catalytic domains of human CDC25 or mouse SOS1, either alone (designated cCDC25 and cSOS1, respectively) or terminating in the carboxyl-terminal CAAX membrane-targeting sequence from K-Ras4B (designated cCDC25-CAAX and cSOS1-CAAX, respectively; in CAAX, C is Cys, A is an aliphatic amino acid, and X is Ser or Met). We then compared the transforming potential of cCDC25 and cSOS1 with their membrane-targeted counterparts. We observed that addition of the Ras plasma membrane-targeting sequence to the catalytic domains of CDC25 and SOS1 greatly enhanced their focus-forming activity (10-to 50-fold) in NIH 3T3 transfection assays. Similarly, we observed that the membrane-targeted versions showed a 5-to 10-fold enhanced ability to induce transcriptional activation from the Ets/AP-1 Rasresponsive element. Furthermore, whereas cells that stably expressed cCDC25 or cSOSl exhibited the same morphologies as untransformed NIH 3T3 cells, cells expressing cCDC25-CAAX or cSOSl-CAAX displayed transformed morphologies that were indis hable from the elongated and refractile morphology of oncogenic Ras-transformed cells. Thus, these results suggest that membrane translocation alone is sufficient to potentiate guanine nucleotide exchange factor activation of Ras.Ras proteins are GDP/GTP-binding proteins that function as molecular switches to mediate downstream signaling from a diverse variety of extracellular stimuli that influence cell growth and differentiation (1). Ras activity is controlled by a GDP/GTP cycle that is negatively regulated by GTPase-activating proteins (GAPs; p120 and NF1 GAP) that stimulate the intrinsic GTPase activity of Ras to promote formation of the inactive GDP-bound state of Ras and positively regulated by guanine nucleotide exchange factors (GEFs; CDC25/GRF and SOS1/2) that promote exchange of GDP for GTP to attain the active conformation (2). While mitogen-stimulated elevations in Ras-GTP are believed to occur primarily as a consequence of the activation of Ras GEFs, the precise mechanism for this activation remains unresolved (9). Recent studies identifying the role of SOS1 in mediating epidermal growth factor (EGF)-triggered activation of Ras have suggested a mechanism whereby recruitment to the plasma membrane may be sufficient to cause Ras activation (10-17). In quiescent Rat-i fibroblasts, SOS1 was found almost exclusively in the cytosolic fraction. However, upon EGF stimulation, Buday and Downward (12) observed that the majority of SOS1 was translocated to the particulate fraction and was found to be associated with...

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“…We and others have shown that Ras GEFs can stimulate the activity of wild-type Ras to activate transcription from Ras-responsive promoter elements (8,43,44). To determine if FGD1 regulates transcriptional activation via direct stimulation of CDC42, we measured FGD1 activation of the Elk-1, Jun, and SRF reporters in the presence of wild-type CDC42.…”

Section: Fgd1mentioning

confidence: 99%

CDC42 and FGD1 Cause Distinct Signaling and Transforming Activities

Whitehead

Abe

Gorski

et al. 1998

Molecular and Cellular Biology

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Activated forms of different Rho family members (CDC42, Rac1, RhoA, RhoB, and RhoG) have been shown to transform NIH 3T3 cells as well as contribute to Ras transformation. Rho family guanine nucleotide exchange factors (GEFs) (also known as Dbl family proteins) that activate CDC42, Rac1, and RhoA also demonstrate oncogenic potential. The faciogenital dysplasia gene product, FGD1, is a Dbl family member that has recently been shown to function as a CDC42-specific GEF. Mutations within the FGD1 locus cosegregate with faciogenital dysplasia, a multisystemic disorder resulting in extensive growth impairments throughout the skeletal and urogenital systems. Here we demonstrate that FGD1 expression is sufficient to cause tumorigenic transformation of NIH 3T3 fibroblasts. Although both FGD1 and constitutively activated CDC42 cooperated with Raf and showed synergistic focus-forming activity, both quantitative and qualitative differences in their functions were seen. FGD1 and CDC42 also activated common nuclear signaling pathways. However, whereas both showed comparable activation of c-Jun, CDC42 showed stronger activation of serum response factor and FGD1 was consistently a better activator of Elk-1. Although coexpression of FGD1 with specific inhibitors of CDC42 function demonstrated the dependence of FGD1 signaling activity on CDC42 function, FGD1 signaling activities were not always consistent with the direct or exclusive stimulation of CDC42 function. In summary, FGD1 and CDC42 signaling and transformation are distinct, thus suggesting that FGD1 may be mediating some of its biological activities through non-CDC42 targets.The Rho subfamily of Ras-related GTPases (14 mammalian members) controls multiple aspects of cell behavior, including cytoskeletal rearrangement, nuclear signaling, and cell growth (reviewed in reference 67). For example, CDC42 mediates the induction of actin microspikes and filopodia by bradykinin (26, 33), whereas Rac1 is required for growth factor-induced membrane ruffling and lamellipodia formation (47). In contrast, RhoA regulates the formation of actin stress fibers (46). In Swiss 3T3 cells, the assembly of these structures involves a cascade in which CDC42 activates Rac1, which in turn activates RhoA (33). Rho family proteins also have demonstrated roles in the regulation of gene expression as measured by (i) the transcriptional activation of the serum response factor (SRF) (19), (ii) activation of c-Jun NH 2 -terminal kinase (JNK) and its downstream target c-Jun (10, 32, 35), (iii) activation of the ternary complex factor protein Elk-1 (62), (iv) activation of p38/Mpk2 (63), and (v) regulation of expression from the cyclin D1 promoter (55). Finally, there is growing evidence that the deregulated expression of Rho family members has profound effects on the proliferative potential of cells. Activated derivatives of RhoA, RhoB, Rac1, and CDC42 cause oncogenic transformation when expressed in rodent fibroblast cell lines and may contribute to Ras-mediated malignant transformation (23,39,41,42,53,...

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Saccharomyces cerevisiae CDC25 [1028–1589] is a guanine nucleotide exchange factor for mammalian ras proteins and is ongenic in HIH3T3 cells

Cited by 7 publications

References 0 publications

An Evolutionarily Conserved Domain in a Subfamily of Rabs Is Crucial for the Interaction with the Guanyl Nucleotide Exchange Factor Mss4

An Evolutionarily Conserved Domain in a Subfamily of Rabs Is Crucial for the Interaction with the Guanyl Nucleotide Exchange Factor Mss4

Membrane-targeting potentiates guanine nucleotide exchange factor CDC25 and SOS1 activation of Ras transforming activity.

CDC42 and FGD1 Cause Distinct Signaling and Transforming Activities

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