Suppression of Raf-1 kinase activity and MAP kinase signalling by RKIP.
Raf-1 phosphorylates and activates MEK-1, a kinase that activates the extracellular signal regulated kinases (ERK). This kinase cascade controls the proliferation and differentiation of different cell types. Here we describe a Raf-1-interacting protein, isolated using a yeast two-hybrid screen. This protein inhibits the phosphorylation and activation of MEK by Raf-1 and is designated RKIP (Raf kinase inhibitor protein). In vitro, RKIP binds to Raf-1, MEK and ERK, but not to Ras. RKIP co-immunoprecipitates with Raf-1 and MEK from cell lysates and colocalizes with Raf-1 when examined by confocal microscopy. RKIP is not a substrate for Raf-1 or MEK, but competitively disrupts the interaction between these kinases. RKIP overexpression interferes with the activation of MEK and ERK, induction of AP-1-dependent reporter genes and transformation elicited by an oncogenically activated Raf-1 kinase. Downregulation of endogenous RKIP by expression of antisense RNA or antibody microinjection induces the activation of MEK-, ERK- and AP-1-dependent transcription. RKIP represents a new class of protein-kinase-inhibitor protein that regulates the activity of the Raf/MEK/ERK module.
Yeung
K
K
Brown University, Department of Molecular Biology, Cell Biology and Biochemistry, Richmond 02912, USA.
Seitz
T
T
Li
S
S
Janosch
P
P
McFerran
B
B
Kaiser
C
C
Fee
F
F
Katsanakis
K D
KD
Rose
D W
DW
Mischak
H
H
Sedivy
J M
JM
Kolch
W
W
D016475:3T3 Cells; D000727:Androgen-Binding Protein; D000818:Animals; D019556:COS Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D003001:Cloning, Molecular; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics; D048728:MAP Kinase Kinase Kinase 1; D051379:Mice; D049488:Phosphatidylethanolamine Binding Protein; D049294:Phospholipid Transfer Proteins; D060789:Prostatein; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D060765:Secretoglobins; D015398:Signal Transduction / Q000187:drug effects*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014598:Uteroglobin; D060788:Mammaglobin B
D000727:Androgen-Binding Protein; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D048728:MAP Kinase Kinase Kinase 1; D049488:Phosphatidylethanolamine Binding Protein; D049294:Phospholipid Transfer Proteins; D060789:Prostatein; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D011994:Recombinant Proteins; D060765:Secretoglobins; D018808:Transcription Factor AP-1; D014598:Uteroglobin; C511482:PEBP1 protein, human; C511484:Scgb1d2 protein, rat; C511483:Scgb1d4 protein, rat; C482576:MAP3K1 protein, human; C482578:Map3k1 protein, mouse; C556468:Scgb2a1 protein, rat; D060788:Mammaglobin B