title: The interplay between Eps8 and IRSp53 contributes to Src-mediated transformation.
abstract: As an oncoprotein, Eps8 participates in v-Src-induced cellular transformation. To delineate the underlying mechanism, we conducted a yeast two-hybrid screening and identified IRSp53S, a protein critical in cell mobilization, as one of the Eps8-binding partners from a human brain cDNA library. The association was mediated by the multiple proline-rich regions of Eps8 and the C-terminal SH3-WWB containing domains of IRSp53S. In this study, we observed that Eps8 modulated the expression of IRSp53 in v-Src-transformed cells (IV5), raising the question of whether Eps8/IRSp53 interaction was crucial in carcinogenesis. To address this issue, we generated IV5-expressing irsp53 siRNA cells. Attenuation of IRSp53 reduced cell proliferation of IV5 in culture dish and tumor formation in mice, which could be partly rescued by ectopically expressed human IRSp53S. In addition, IRSp53 knockdown impaired activity of phosphatidylinositol 3-kinase (as reflected by Pi-Ser473 AKT) and Stat3 (as reflected by Pi-Tyr705 Stat3), and reduced cyclin D1 expression that culminated to impede G(1)-phase cell-cycle progression. Ectopically expressed human IRSp53S, but not its Eps8-binding defective mutants (that is, Delta363 and PPPDA), rescued these defects and partly restored cell proliferation. Remarkably, through activation of Src, EGF increased the formation of Eps8/IRSp53 complex and Stat3 activation in HeLa cells. With these results, we show for the first time that IRSp53, through its interaction with Eps8, not only affects cell migration but also dictates cellular growth in cancer cells.
authors.affiliation: Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: P-S
authors.initials: PS
authors.lastname: Liu
authors.forename: T-H
authors.initials: TH
authors.lastname: Jong
authors.forename: M-C
authors.initials: MC
authors.lastname: Maa
authors.forename: T-H
authors.initials: TH
authors.lastname: Leu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002453:Cell Cycle; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D019938:Cyclin D1 / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D050796:STAT3 Transcription Factor / Q000378:metabolism; D017384:Sequence Deletion; D020798:Two-Hybrid System Techniques
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C119539:BAIAP2 protein, human; C489989:EPS8 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; D019938:Cyclin D1; D004815:Epidermal Growth Factor; D015688:Oncogene Protein pp60(v-src); D051057:Proto-Oncogene Proteins c-akt