IRSp53/Eps8 complex is important for positive regulation of Rac and cancer cell motility/invasiveness.
IRSp53 has been characterized as an adaptor protein that links Rho-family small GTPases, such as Rac, to reorganization of the actin cytoskeleton. Here, we search for other binding partners for the IRSp53 SH3 domain and identify Eps8 as the major binding protein in fibroblasts and various cancer cell lines. Eps8 has been shown to form a Rac-specific guanine nucleotide exchange factor complex with Abi-1 and Sos-1, which seems essential for ruffling formation induced by oncogenic Ras. We confirm the IRSp53/Eps8 complex formation in vivo and the direct association between Eps8 NH(2)-terminal proline-rich sequence and IRSp53 SH3 domain. This complex synergistically activates Rac by reinforcing the formation of the Eps8/Abi-1/Sos-1 Rac-guanine nucleotide exchange factor complex, which mediates positive regulation of Rac activity. In addition, IRSp53/Eps8 complex formation as determined by fluorescent resonance energy transfer analysis, occurs at the leading edge of motile cells, and the motility and invasiveness of HT1080 fibrosarcoma cells are suppressed by inhibiting complex formation. These findings implicate the importance of the IRSp53/Eps8 complex in Rac activation and metastatic behavior of the malignant tumor cells.
Division of Cancer Genomics, Biochemistry, and Cancer Cell Research, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
Yosuke
Y
Funato
Takeshi
T
Terabayashi
Naoko
N
Suenaga
Motoharu
M
Seiki
Tadaomi
T
Takenawa
Hiroaki
H
Miki
D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D002465:Cell Movement; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton; D005354:Fibrosarcoma / Q000378:metabolism* / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008546:Melanoma, Experimental / Q000378:metabolism / Q000473:pathology; D051379:Mice; D009361:Neoplasm Invasiveness; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D020837:SOS1 Protein / Q000378:metabolism; D015398:Signal Transduction; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism; D018909:src Homology Domains
C513733:ABI1 protein, human; C513734:Abi1 protein, mouse; D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C119539:BAIAP2 protein, human; D003598:Cytoskeletal Proteins; C489989:EPS8 protein, human; C083430:Eps8 protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; D020837:SOS1 Protein; D020744:rac GTP-Binding Proteins; D018631:ras Proteins