Guanine nucleotide exchange factors regulate specificity of downstream signaling from Rac and Cdc42.
The Rac and Cdc42 GTPases regulate diverse cellular behaviors involving the actin cytoskeleton, gene transcription, and the activity of multiple protein and lipid kinases. All of these pathways can potentially become activated when GTP-Rac or GTP-Cdc42 is formed in response to external cell signals, yet it is evident that each activity must also be able to be controlled individually. The mechanisms by which such specificity of GTPase signaling in response to upstream stimuli is achieved remains unclear. We investigated the action of several well characterized guanine nucleotide exchange factors (GEFRho) to activate Rac- and/or Cdc42-dependent kinase pathways. Coexpression studies in COS-7 cells revealed that the ability of individual guanine nucleotide exchange factors (GEFs) to activate the p21-activated kinase PAK1 could be dissociated from activation of c-Jun amino-terminal kinase, even though activation of both pathways requires the action of the GEFs on Rac and/or Cdc42. In contrast, expression of constitutively active forms of Rac or Cdc42 effectively stimulated both downstream kinases. We conclude that GEFs can be important determinants of downstream signaling specificity for members of the Rho GTPase family.
Zhou
K
K
Departments of Immunology and Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Wang
Y
Y
Gorski
J L
JL
Nomura
N
N
Collard
J
J
Bokoch
G M
GM
D000818:Animals; D019556:COS Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins
D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D011506:Proteins; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins