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Dynamics of integrin clustering at focal contacts of endothelial cells studied by multimode imaging microscopy

K Kawakami1, H Tatsumi, M Sokabe

  • 1Department of Physiology, Nagoya University Graduate School of Medicine, 65 Tsurumai Showa-ku, Nagoya Aichi 4668550, Japan.

Journal of Cell Science
|October 9, 2001
PubMed

Insights

Integrin clustering in endothelial cells drives focal contact formation. Actin fibers guide integrin movement to focal contact tips, revealing a novel mechanism for cell adhesion and migration.

Area of Science:

  • Cell Biology
  • Biophysics
  • Integrin Signaling

Background:

  • Focal contacts are crucial for cell adhesion and migration.
  • Integrin clustering is a key event in focal contact formation, but its precise mechanism remains unclear.

Purpose of the Study:

  • To elucidate the mechanism of integrin clustering during focal contact formation in human umbilical vein endothelial cells.
  • To investigate the role of intracellular components and cellular structures in integrin dynamics at focal contacts.

Main Methods:

  • Time-lapse total-internal-reflection fluorescence microscopy to visualize labeled integrins in living cells.
  • Photobleaching and recovery experiments to track integrin dynamics.
  • Simultaneous imaging of exocytosis and focal contact elongation.
  • Double staining for F-actin and integrins.

Main Results:

  • Integrin clustering began 1 hour after plating and clusters grew for approximately 6 hours.
  • 80% of integrin clusters elongated towards the cell center or margin.
  • Integrins at cluster tips were supplied from intracellular spaces via exocytosis.
  • Stress fibers were located near integrin clusters, and intracellular integrins associated with these fibers.

Conclusions:

  • Integrin clustering is mediated by actin-fiber-dependent translocation of integrins to the extending tip of focal contacts.
  • Exocytosis of integrin-containing vesicles fuels focal contact elongation.
  • This study reveals a dynamic mechanism for focal contact assembly involving directed integrin transport.

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