An interaction between insulin-like growth factor-binding protein 2 (IGFBP2) and integrin alpha5 is essential for IGFBP2-induced cell mobility.
In the study we report here, we tested the hypothesis that insulin-like growth factor-binding protein 2 (IGFBP2) promotes cell mobility through its interaction with integrin alpha5. Our previous microarray studies showed that IGFBP2 activates the expression of integrin alpha5. In addition, IGFBP2 has an Arg-Gly-Asp (RGD) domain, which is a known integrin binding motif. We first confirmed our microarray results by showing that the expression of integrin alpha5 is indeed up-regulated at the protein level in IGFBP2-overexpressing SNB19 glioma cells. Using co-immunoprecipitation, we confirmed that IGFBP2 does interact with integrin alpha5. To confirm that IGFBP2 interacts directly with integrin alpha5 through the RGD domain, we created an RGD --> RGE mutant (D306E) IGFBP2 and stably overexpressed the mutant IGFBP2 in the same cell line. Co-immunoprecipitation then showed that D306E-IGFBP2 had no detectable binding with integrin alpha5. We further observed that IGFBP2-overexpressing cells have extensive cell surface lamellipodia, whereas D306E-IGFBP2-overexpressing cells show abundant cell surface focal adhesions. Consistent with this, phenotype analysis then showed that IGFBP2-overexpressing cells have elevated migration rates compared with vector control; in contrast, the migration rates of the D306E-IGFBP2-overexpressing cells were not elevated and were comparable with that of vector control. Decreased expression of integrin alpha5 by small interference RNA in IGFBP2-overexpressing cells also reduced cell mobility. Therefore, we have concluded that one mechanism by which IGFBP2 activates IGFBP2-induced cell mobility is through its interaction with integrin alpha5 and this interaction is specifically mediated through the RGD domain on IGFBP2.
Wang
George K
GK
Department of Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Hu
Limei
L
Fuller
Gregory N
GN
Zhang
Wei
W
D001483:Base Sequence; D045744:Cell Line, Tumor; D002465:Cell Movement; D005822:Genetic Vectors; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism*; D039482:Integrin alpha5 / Q000378:metabolism*; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D009842:Oligopeptides / Q000737:chemistry; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000378:metabolism; D015854:Up-Regulation
D018971:Insulin-Like Growth Factor Binding Protein 2; D039482:Integrin alpha5; D009842:Oligopeptides; D034741:RNA, Small Interfering; C047981:arginyl-glycyl-aspartic acid