Live-cell monitoring of tyrosine phosphorylation in focal adhesions following microtubule disruption.
Tyrosine phosphorylation of focal adhesion components is involved in the regulation of focal adhesion formation and turnover, yet the underlying molecular mechanisms are still poorly defined. In the present study, we have used quantitative fluorescence microscopy to investigate the dynamic relationships between the incorporation of new components into growing focal adhesions and tyrosine phosphorylation of these sites. For this purpose, a new approach for monitoring phosphotyrosine levels in live cells was developed, based on a 'phosphotyrosine reporter' consisting of yellow fluorescent protein fused to two consecutive phosphotyrosine-binding Src-homology 2 (SH2)-domains derived from pp60(c-Src). This YFP-dSH2 localized to cell-matrix adhesions and its intensity was linearly correlated with that of an anti-phosphotyrosine antibody labeling. The differential increase in vinculin and phosphotyrosine levels was examined in live cells by two-color time-lapse movies of CFP-vinculin and YFP-dSH2. In this study, focal adhesion growth was triggered by microtubule disruption, which was previously shown to stimulate focal adhesion development by inducing cellular contraction. We show here that, 2 minutes after addition of the microtubule-disrupting drug nocodazole, the local densities of the focal adhesion-associated proteins vinculin, paxillin and focal adhesion kinase (FAK) are significantly elevated and the focal adhesion area is increased, whereas elevation in tyrosine phosphorylation inside the growing adhesions occurs only a few minutes later. Phosphotyrosine and FAK density reach their maximum levels after 10 minutes of treatment, whereas vinculin and paxillin levels as well as focal adhesion size continue to grow, reaching a plateau at about 30 minutes. Our findings suggest that protein recruitment and growth of focal adhesions are an immediate and direct result of increased contractility induced by microtubule disruption, whereas tyrosine phosphorylation is activated later.
Kirchner
Jochen
J
Department of Molecular Cell Biology, The Weizmann Institute of Science, 76100 Rehovot, Israel.
Kam
Zvi
Z
Tzur
Gila
G
Bershadsky
Alexander D
AD
Geiger
Benjamin
B
D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000494:pharmacology; D002460:Cell Line; D003584:Cytological Techniques; D003598:Cytoskeletal Proteins / Q000378:metabolism; D051416:Focal Adhesion Protein-Tyrosine Kinases; D022001:Focal Adhesions / Q000187:drug effects / Q000378:metabolism*; D017930:Genes, Reporter; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D015739:Nocodazole / Q000494:pharmacology; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D016596:Vinculin / Q000378:metabolism; D018909:src Homology Domains / Q000235:genetics
D000970:Antineoplastic Agents; D003598:Cytoskeletal Proteins; D051419:Paxillin; D010750:Phosphoproteins; D016596:Vinculin; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051416:Focal Adhesion Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); D015739:Nocodazole