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.
Department of Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
George K
GK
Wang
Limei
L
Hu
Gregory N
GN
Fuller
Wei
W
Zhang
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