Sequential signals toward podosome formation in NIH-src cells.
Podosomes (also termed invadopodia in cancer cells) are actin-rich adhesion structures with matrix degradation activity that develop in various cell types. Despite their significant physiological importance, the molecular mechanism of podosome formation is largely unknown. In this study, we investigated the molecular mechanisms of podosome formation. The expression of various phosphoinositide-binding domains revealed that the podosomes in Src-transformed NIH3T3 (NIH-src) cells are enriched with PtdIns(3,4)P2, suggesting an important role of this phosphoinositide in podosome formation. Live-cell imaging analysis revealed that Src-expression stimulated podosome formation at focal adhesions of NIH3T3 cells after PtdIns(3,4)P2 accumulation. The adaptor protein Tks5/FISH, which is essential for podosome formation, was found to form a complex with Grb2 at adhesion sites in an Src-dependent manner. Further, it was found that N-WASP bound all SH3 domains of Tks5/FISH, which facilitated circular podosome formation. These results indicate that augmentation of the N-WASP-Arp2/3 signal was accomplished on the platform of Tks5/FISH-Grb2 complex at focal adhesions, which is stabilized by PtdIns(3,4)P2.
Oikawa
Tsukasa
T
Division of Lipid Biochemistry, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan.
Itoh
Toshiki
T
Takenawa
Tadaomi
T
D000199:Actins / Q000378:metabolism; D000818:Animals; D002461:Cell Line, Transformed; D022081:Cell Surface Extensions / Q000378:metabolism*; D002470:Cell Survival; D004789:Enzyme Activation; D022001:Focal Adhesions / Q000201:enzymology; D051380:GRB2 Adaptor Protein / Q000378:metabolism; D051379:Mice; D009154:Mutation / Q000235:genetics; D041681:NIH 3T3 Cells; D028044:Phosphate-Binding Proteins; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D021381:Protein Transport; D017385:Sequence Homology; D015398:Signal Transduction; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000737:chemistry; D019061:src-Family Kinases / Q000378:metabolism*
D000199:Actins; C114235:Fish protein, mouse; D051380:GRB2 Adaptor Protein; D028044:Phosphate-Binding Proteins; D018129:Phosphatidylinositol Phosphates; D010750:Phosphoproteins; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; C060980:phosphatidylinositol 3,4-diphosphate; D019061:src-Family Kinases