RhoA binds to the amino terminus of MEKK1 and regulates its kinase activity.
MEKK1 is a mitogen-activated protein kinase kinase kinase (MAP3K) that can regulate the c-Jun amino-terminal kinase (JNK) MAP kinase cascade. MEKK1 is comprised of a kinase domain and a long amino-terminal regulatory domain. This amino-terminal domain has a scaffold function in that it can assemble modules of the JNK and ERK MAP kinase cascades. Recently, we have demonstrated that MEKK1 binds to p115 Rho GTPase-activating protein, which has GTPase-activating protein activity toward RhoA. Thus, we tested whether Rho GTPases interact with the regulatory domain of MEKK1. RhoA, but not Rac or Cdc42, binds to a site in the aminoterminal one-third of MEKK1, which includes its PHD domain. The interaction is prevented by mutation of the essential cysteine in the MEKK1 PHD domain. Rho-GTP stimulates the kinase activity of full-length MEKK1 as much as 10-fold toward MEK4 but does not appear to be ubiquitinated by MEKK1 under conditions that result in modification of ERK2. In summary, we have characterized a novel point at which Rho GTPases impinge upon the regulation and function of MEKK1.
Department of Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9041, USA.
Ewen D
ED
Gallagher
Stephen
S
Gutowski
Paul C
PC
Sternweis
Melanie H
MH
Cobb
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D004285:Dogs; D006801:Humans; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D025801:Ubiquitin / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D025801:Ubiquitin; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases; C482576:MAP3K1 protein, human; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein