University of Illinois Urbana-Champaign

Rapid Rac GTP-ASE activation in live cells by mechanical stress is independent of Src

Poh, Yeh Chuin

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1_Poh_Yeh Chuin.pdf

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https://hdl.handle.net/2142/14725

Description

Title
Rapid Rac GTP-ASE activation in live cells by mechanical stress is independent of Src
Author(s)
Poh, Yeh Chuin
Issue Date
2010-01-06T16:41:58Z
Director of Research (if dissertation) or Advisor (if thesis)
Wang, Ning
Doctoral Committee Chair(s)
Wang, Ning
Department of Study
Mechanical Sci & Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Date of Ingest
2010-01-06T16:41:58Z
Keyword(s)
  • growth factor
  • mechanotransduction
  • signal transduction
  • deformation
  • mechanical stress
Abstract
It is well-known that mechanical forces are crucial in regulating functions of every tissue and organ in a human body. However, it remains unclear how mechanical forces are transduced into biochemical activities and biological responses at the cellular and molecular level. Using the magnetic twisting cytometry technique, we applied local mechanical stresses to living human airway smooth muscle cells with a magnetic bead bound to the cell surface via transmembrane adhesion molecule integrins. The temporal and spatial activation of Rac, a small guanosine triphosphatase, was quantified using a fluorescent resonance energy transfer (FRET) method that measures changes in Rac activity in response to mechanical stresses by quantifying intensity ratios of ECFP (enhanced cyan fluorescent protein as a donor) and YPet (a variant yellow fluorescent protein as an acceptor) of the Rac biosensor. The applied stress induced rapid activation (less than 300 ms) of Rac at the cell periphery. In contrast, platelet derived growth factor (PDGF) induced Rac activation at a much later time (>30 sec). It is known that PDGF-induced Rac activation depends on Src activity. There was no stress-induced Rac activation when a mutant form of the Rac biosensor (RacN17) was transfected or when the magnetic bead was coated with transferrin or with poly-L-lysine. Surprisingly, pre-treatment of the cells with specific Src inhibitor PP1 or knocking-out Src gene had no effects on stress-induced Rac activation. In addition, eliminating lipid rafts through extraction of cholesterol from the plasma membrane did not prevent stress-induced Rac activation, suggesting a raft-independent mechanism in governing the Rac activation upon mechanical stimulation. Further evidence indicates that Rac activation by stress depends on the magnitudes of the applied stress and cytoskeletal integrity. Our results suggest that Rac activation by mechanical forces is rapid, direct and does not depend on Src activation. These findings suggest that signaling pathways of mechanical forces might be fundamentally different from those of growth factors.
Graduation Semester
2009-12
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http://hdl.handle.net/2142/14725
Copyright and License Information
Copyright 2009 Yeh Chuin Poh

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