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

Poh, Yeh Chuin

Permalink

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

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

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

Permalink

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

Copyright and License Information

Copyright 2009 Yeh Chuin Poh

Owning Collections