Differential regulation of cortactin and N-WASP-mediated actin polymerization by missing in metastasis (MIM) protein.
Missing in metastasis (MIM) gene encodes an actin binding protein that is expressed at low levels in a subset of malignant cell lines. MIM protein tagged by green fluorescent protein (GFP) colocalizes with cortactin, an Arp2/3 complex activator, and interacts directly with the SH3 domain of cortactin. Recombinant full-length MIM promotes markedly cortactin and Arp2/3 complex-mediated actin polymerization in an SH3 dependent manner. In contrast, MIM-CT, a short splicing variant of MIM, binds poorly to cortactin in vitro and is unable to enhance actin polymerization. Full-length MIM binds to G-actin with a similar affinity as N-WASP-VCA, a constitutively active form of N-WASP, and inhibits N-WASP-VCA-mediated actin polymerization as analysed in vitro. The significance of the association of MIM with cortactin and G-actin was evaluated in NIH3T3 cells expressing several MIM constructs. Overexpression of full-length wild-type MIM-GFP inhibited markedly the motility of NIH3T3 cells induced by PDGF and that of human vein umbilical endothelial cells induced by sphingosine 1 phosphate. However, an MIM mutant with deletion of the WH2 domain, which is responsible for G-actin binding, enhanced cell motility. The motility inhibition imposed by MIM was compromised in the cells overexpressing N-WASP. In contrast, deletion of an MIM proline-rich domain, which is required for an optimal binding to cortactin, substantiated the MIM-mediated inhibition of cell motility. These data imply that MIM regulates cell motility by modulating different Arp2/3 activators in a distinguished manner.
Lin
Jinxiu
J
Holland Laboratory, American Red Cross, 15601 Crabbs Branch Way, Rockville, MD 20855, USA.
Liu
Jiali
J
Wang
Ying
Y
Zhu
Jianwei
J
Zhou
Kang
K
Smith
Nicole
N
Zhan
Xi
X
D016475:3T3 Cells; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D051356:Cortactin; D005786:Gene Expression Regulation; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D017384:Sequence Deletion; D014471:Umbilical Veins; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal
D000199:Actins; D051356:Cortactin; C495869:Cttn protein, mouse; D008840:Microfilament Proteins; C473219:Mtss1 protein, mouse; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010982:Platelet-Derived Growth Factor; C495772:Wasl protein, mouse; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal