title: Calcium oscillations trigger focal adhesion disassembly in human U87 astrocytoma cells.
abstract: Integrin-associated intracellular Ca(2+) oscillations modulate cell migration, probably by controlling integrin-mediated release of the cell rear during migration. Focal adhesion kinase (FAK), via its tyrosine phosphorylation activity, plays a key role in integrin signaling. In human U87 astrocytoma cells, expression of the dominant negative FAK-related non-kinase domain (FRNK) inhibits the Ca(2+)-sensitive component of serum-dependent migration. We investigated how integrin-associated Ca(2+) signaling might be coupled to focal adhesion (FA) dynamics by visualizing the effects of Ca(2+) spikes on FAs using green fluorescent protein (GFP)-tagged FAK and FRNK. We report that Ca(2+) spikes are temporally correlated with movement and disassembly of FAs, but not their formation. FRNK transfection did not affect generation of Ca(2+) spikes, although cell morphology was altered, with fewer FAs of larger size and having a more peripheral localization being observed. Larger sized FAs in FRNK-transfected cells were not disassembled by Ca(2+) spikes, providing a possible explanation for impaired Ca(2+)-dependent migration in these cells. Stress fiber end movements initiated by Ca(2+) spikes were visualized using GFP-tagged myosin light chain kinase (MLCK). Ca(2+)-associated movements of stress fiber ends and FAs had similar kinetics, suggesting that stress fibers and FAs move in a coordinated fashion. This indicates that increases in Ca(2+) likely trigger disassembly of adhesive structures that involves disruption of integrin-extracellular matrix interactions, supporting a key role for Ca(2+)-sensitive inside-out signaling in cell migration. A rapid increase in tyrosine phosphorylation of FAK was found in response to an elevation in Ca(2+) induced by thapsigargin, and we propose that this represents the initial triggering event linking Ca(2+) signaling and FA dynamics to cell motility.
authors: Laboratoire de Pharmacologie et Physicochimie des Interactions Cellulaires et Moléculaires, UMR CNRS 7034, Université Louis Pasteur de Strasbourg, 67401 Illkirch, France.
authors: Gregory
authors: G
authors: Giannone
authors: Philippe
authors: P
authors: Rondé
authors: Mireille
authors: M
authors: Gaire
authors: Jacques
authors: J
authors: Haiech
authors: Kenneth
authors: K
authors: Takeda
mesh_terms: D001254:Astrocytoma / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002465:Cell Movement / Q000187:drug effects; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism
chemical_list: D014443:Tyrosine; D019284:Thapsigargin; C113183:FAK-related nonkinase; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D009219:Myosin-Light-Chain Kinase; D002118:Calcium