X-linked and cellular IAPs modulate the stability of C-RAF kinase and cell motility.
Inhibitor of apoptosis proteins (IAP) are evolutionarily conserved anti-apoptotic regulators. C-RAF protein kinase is a direct RAS effector protein, which initiates the classical mitogen-activated protein kinase (MAPK) cascade. This signalling cascade mediates diverse biological functions, such as cell growth, proliferation, migration, differentiation and survival. Here we demonstrate that XIAP and c-IAPs bind directly to C-RAF kinase and that siRNA-mediated silencing of XIAP and c-IAPs leads to stabilization of C-RAF in human cells. XIAP binds strongly to C-RAF and promotes the ubiquitylation of C-RAF in vivo through the Hsp90-mediated quality control system, independently of its E3 ligase activity. In addition, XIAP or c-IAP-1/2 knockdown cells showed enhanced cell migration in a C-RAF-dependent manner. XIAP promotes binding of CHIP (carboxy terminal Hsc70-interacting protein), a chaperone-associated ubiquitin ligase, to the C-RAF-Hsp90 complex in vivo. Interfering with CHIP expression resulted in stabilization of C-RAF and enhanced cell migration, as observed in XIAP knockdown cells. Our data show an unexpected role of XIAP and c-IAPs in the turnover of C-RAF protein, thereby modulating the MAPK signalling pathway and cell migration.
Dogan
Taner
T
Emmy Noether Group of DFG, Institut für Biochemie II, Goethe University Medical School, Frankfurt, Germany.
Harms
Gregory S
GS
Hekman
Mirko
M
Karreman
Christiaan
C
Oberoi
Tripat Kaur
TK
Alnemri
Emad S
ES
Rapp
Ulf R
UR
Rajalingam
Krishnaraj
K
D002465:Cell Movement; D004795:Enzyme Stability; D020868:Gene Silencing; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D011485:Protein Binding; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D014162:Transfection; D044767:Ubiquitin-Protein Ligases; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism*
D018841:HSP90 Heat-Shock Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; D044767:Ubiquitin-Protein Ligases; D019908:Proto-Oncogene Proteins c-raf