Calcium oscillations trigger focal adhesion disassembly in human U87 astrocytoma cells

J Biol Chem. 2002 Jul 19;277(29):26364-71. doi: 10.1074/jbc.M203952200. Epub 2002 May 14.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Astrocytoma / metabolism*
  • Calcium / metabolism*
  • Cell Movement / drug effects
  • Focal Adhesion Kinase 1
  • Focal Adhesion Protein-Tyrosine Kinases
  • Humans
  • Myosin-Light-Chain Kinase / metabolism
  • Phosphorylation
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism*
  • Thapsigargin / pharmacology
  • Transfection
  • Tumor Cells, Cultured
  • Tyrosine / metabolism

Substances

  • Tyrosine
  • Thapsigargin
  • FAK-related nonkinase
  • Protein-Tyrosine Kinases
  • Focal Adhesion Kinase 1
  • Focal Adhesion Protein-Tyrosine Kinases
  • PTK2 protein, human
  • Myosin-Light-Chain Kinase
  • Calcium