Molecular Mechanisms of Regulation of Contraction

Project Details


DESCRIPTION: (provided by applicant): Regulation of the actin cytoskeleton by
cell signaling pathways is important for cellular movement and function. The
activation of one Rho GTPase, Cdc42, leads to the rapid and transient
polymerization of a highly-branched actin network nucleated by Arp2/3 complex.
The event creates a myosin-independent force that pushes forward the membrane
at the leading edge of motile cells. While much is known about the activation
and deactivation of this process, important questions remain. How is formation
of branched networks localized to the leading edge of the cell and not from
actin filaments deeper in the cortex and in stress fibers? What protects
selected populations of actin filaments from severing and pointed-end
depolymerization by ADF/cofilin? Is there a hierarchy of filament stability?
The goal of the research is to understand the cascade of events leading to the
formation and maintenance of stable actin filaments in the cell. The research
will explore the roles of ADF/cofilin, Arp2/3 complex, tropomyosin and
tropomodulin, together with the actin nucleotide, in defining the pathway from
nascent, branched actin filaments to stable filaments. There are four specific
aims. 1) How are branched filaments converted to stable unbranched filaments
and how do long, unbranched filaments remain unbranched?2) How are the pointed
ends of stable actin filaments protected from depolymerization?3) How are long
actin filaments in the deep cell cortex and stress fibers protected from
severing and pointed end depolymerization by ADF/cofilin while those in the
branched actin network are not?4) To determine the localization of tropomyosin
isoforms in relation to Arp2/3 complex, cofilin, and regions of dynamic
remodeling of the actin cytoskeleton.

The methods for Aims 1-3 include measurement of actin polymerization and
depolymerization using actin labeled with a fluorescent probe as well as
microscopic analysis of fluorescently-labeled actin filaments. Aim 4 will
localize the proteins as well as free filament ends in cells using indirect
immunofluorescence. The results will help understand how the cytoskeleton is
remodeled during complex functions such as leucocyte chemotaxis and growth
factor-stimulated cellular outgrowth, processes important in both normal and
pathological states.
Effective start/end date3/1/022/28/07


  • National Institute of General Medical Sciences: $329,510.00
  • National Institute of General Medical Sciences: $304,090.00
  • National Institute of General Medical Sciences: $304,090.00
  • National Institute of General Medical Sciences: $304,090.00


  • Medicine(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Molecular Biology
  • Cell Biology


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