Filamin associates with stress signalling kinases MKK7 and MKK4 and regulates JNK activation.
SAPK/JNK (stress-activated protein kinase/c-Jun N-terminal kinase) belongs to the MAPK (mitogen-activated protein kinase) family and is important in many biological contexts. JNK activation is regulated by phosphorylation of specific tyrosine and threonine residues sequentially catalysed by MKK4 and MKK7, which are both dual-specificity MAPKKs (MAPK kinases). Previously, we reported that tyrosine-phosphorylation of JNK by MKK4 precedes threonine-phosphorylation by MKK7, and that both are required for synergistic JNK activation. In the present study, we identify the actin-binding protein-280 (Filamin A) as a presumed 'binder' protein that can bind to MKK7, as well as to MKK4, connecting them in close proximity. We show that Filamin family members A, B and C interact with MKK4 and MKK7, but not with JNK. Filamin A binds to an N-terminal region (residues 31-60) present in the MKK7gamma and MKK7beta splice isoforms, but cannot bind to MKK7alpha which lacks these amino acids. This same N-terminal region is crucial for the intracellular co-localization of MKK7gamma with actin stress fibres and Filamin A. Experiments using Filamin-A-deletion mutants revealed that the MKK7-binding region of Filamin A differs from its MKK4-binding region, and that MKK7gamma (but not MKK7alpha) can form a complex with Filamin A and MKK4. Finally, we used Filamin-A-deficient cells to show that Filamin A enhances MKK7 activation and is important for synergistic stress-induced JNK activation in vivo. Thus Filamin A is a novel member of the group of scaffold proteins whose function is to link two MAPKKs together and promote JNK activation.
Nakagawa
Kentaro
K
Department of Developmental and Regenerative Biology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan.
Sugahara
Misato
M
Yamasaki
Tokiwa
T
Kajiho
Hiroaki
H
Takahashi
Shinya
S
Hirayama
Jun
J
Minami
Yasuhiro
Y
Ohta
Yasutaka
Y
Watanabe
Toshio
T
Hata
Yutaka
Y
Katada
Toshiaki
T
Nishina
Hiroshi
H
D001665:Binding Sites; D045744:Cell Line, Tumor; D003285:Contractile Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D064448:Filamins; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D048688:MAP Kinase Kinase 7 / Q000378:metabolism*; D008840:Microfilament Proteins / Q000378:metabolism*; D048055:Mitogen-Activated Protein Kinase 8 / Q000378:metabolism*; D011485:Protein Binding; D015398:Signal Transduction; D013312:Stress, Physiological
D003285:Contractile Proteins; C578661:FLNC protein, human; D064448:Filamins; D008840:Microfilament Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D048055:Mitogen-Activated Protein Kinase 8; D048670:MAP Kinase Kinase 4; D048688:MAP Kinase Kinase 7; C482559:MAP2K4 protein, human; C482569:MAP2K7 protein, human