Src kinase activation is mandatory for MDA-9/syntenin-mediated activation of nuclear factor-kappaB.
The scaffolding postsynaptic density-95/disks large/zonula occludens-1 (PDZ) domain-containing protein melanoma differentiation associated gene-9 (MDA-9)/syntenin is a tandem PDZ protein overexpressed in human melanoma, and breast and gastric cancer cells. MDA-9/syntenin affects cancer cell motility and invasion through distinct biochemical and signaling pathways, including focal adhesion kinase and p38 mitogen-activated protein kinase (MAPK), resulting in activation of the nuclear factor (NF)-kappaB pathway. MDA-9/syntenin also promotes melanoma metastasis by activating c-Src, but how c-Src regulates NF-kappaB activation is unclear. Using a human melanoma model, we document that MDA-9/syntenin-c-Src interactions are positive regulators of NF-kappaB activation. Inhibition of c-Src by PP2 treatment, by blocking c-Src or mda-9/syntenin expression with small interfering RNA, or in c-Src (-/-) knockout cell lines, reduces NF-kappaB activation following overexpression of mda-9/syntenin or c-Src. Deletion or point mutations of the PDZ binding motif preventing MDA-9/syntenin association with c-Src reveals that both PDZ domains, with PDZ2 being the dominant module, are required for activating downstream signaling pathways, including p38 MAPK and NF-kappaB. We also document that MDA-9/syntenin-c-Src complexes functionally cooperate with NF-kappaB to promote anchorage-independent growth, motility and invasion of melanoma cells. These findings underscore PDZ domains of MDA-9/syntenin as promising potential therapeutic targets for intervening in a decisive component of cancer progression, namely, metastatic tumor spread.
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Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA, USA. habib.boukerche@sante.univ-lyon1.fr
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D055786:Gene Knockout Techniques; D020868:Gene Silencing; D016391:Genes, src / Q000235:genetics; D006801:Humans; D008545:Melanoma / Q000235:genetics / Q000517:prevention & control; D016328:NF-kappa B / Q000378:metabolism*; D054731:PDZ Domains / Q000235:genetics; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D034741:RNA, Small Interfering / Q000235:genetics; D017384:Sequence Deletion; D053676:Syntenins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation / Q000235:genetics
D016328:NF-kappa B; D010750:Phosphoproteins; D034741:RNA, Small Interfering; C109621:SDCBP protein, human; C108336:SKAP1 protein, human; D053676:Syntenins