A novel potential effector of M-Ras and p21 Ras negatively regulates p21 Ras-mediated gene induction and cell growth.
Here, we report the identification and characterization of a new member of the RalGDS-family, which is widely expressed and interacts strongly and selectively with the GTP-bound forms of M-Ras and p21 Ras. This Ras pathway modulator (RPM), also termed RGL3, exhibited Ras-binding and catalytic domains typical of the RalGDS-family of guanine nucleotide exchange factors, and was most similar to Rlf (RalGDS-like factor), but was distinguished by a unique proline-rich region with multiple candidate SH3-domain binding sites. RPM/RGL3 resembled AF-6 and Nore1 in interacting strongly with constitutively active M-Ras and p21 Ras. In contrast to Rlf, transiently expressed RPM/RGL3 did not activate an Elk-1-inducible reporter gene alone or in combination with activated p21 Ras, but strongly inhibited induction of this reporter gene by co-expression of activated H-Ras or MEKK-1. This inhibitory effect was independent of the Ras binding domain and required a second signal provided by p21 Ras or MEKK-1, but not Raf-1 or M-Ras. Expression of RPM/RGL3 also strongly inhibited cell growth of fibroblasts transformed by an activated Src Y527F. Thus, RPM/RGL3 is a novel potential effector of both p21 Ras and M-Ras with the novel function of negatively regulating Elk-1-dependent gene induction downstream of p21 Ras or MEKK-1.
Ehrhardt
G R
GR
The Biomedical Research Centre, 2222 Health Sciences Mall, University of British Columbia, Vancouver BC, V6T 1Z3 Canada.
Korherr
C
C
Wieler
J S
JS
Knaus
M
M
Schrader
J W
JW
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002455:Cell Division / Q000235:genetics; D002478:Cells, Cultured; D004268:DNA-Binding Proteins; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D048051:p38 Mitogen-Activated Protein Kinases; D020726:ral Guanine Nucleotide Exchange Factor / Q000235:genetics* / Q000378:metabolism*; D018631:ras Proteins; D018909:src Homology Domains; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; C494112:ELK1 protein, human; C494113:Elk1 protein, mouse; D011518:Proto-Oncogene Proteins; C413753:Rgl3 protein, mouse; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D020726:ral Guanine Nucleotide Exchange Factor; D019061:src-Family Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; C482578:Map3k1 protein, mouse; C109418:Mras protein, mouse; C501009:HRAS protein, human; D020559:Monomeric GTP-Binding Proteins; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins