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Related Concept Videos

Small GTPases - Ras and Rho01:24

Small GTPases - Ras and Rho

Ras and Rho are small monomeric GTPases that act downstream of receptor tyrosine kinase (RTK) and regulate various cellular processes. These GTPases switch between active and inactive states by binding to guanine nucleotides.
Three regulatory proteins control their activity:
The Contractile Ring02:15

The Contractile Ring

Contractile rings are composed of microfilaments and are responsible for separating the daughter cells during cytokinesis. Contractile ring assembly proceeds along with other cell cycle events; however, very few mechanistic details are known about the timing and coordination of the contractile rings with the cell cycle.
A small GTPase, RhoA, controls the function and assembly of the contractile ring. RhoA belongs to the Ras superfamily of proteins. The activation of formins by RhoA promotes...
The Contractile Ring02:15

The Contractile Ring

Contractile rings are composed of microfilaments and are responsible for separating the daughter cells during cytokinesis. Contractile ring assembly proceeds along with other cell cycle events; however, very few mechanistic details are known about the timing and coordination of the contractile rings with the cell cycle.
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Rab Cascades01:25

Rab Cascades

Rab GTPases act in a regulated cascade during membrane fusion, helping the lipid bilayers mix. The Rab family of proteins are active when bound to GTP, and inactive when bound to GDP. Hence, they act as guanine nucleotide-dependent molecular switches. Rab-GTP recognizes and binds to long or short-range tethering proteins to capture the target vesicle. These tethers coordinate with SNAREs on the vesicle and the target membrane to assemble the trans SNARE complex that locks the mixing bilayers.
Cell Polarization by Rho Proteins01:21

Cell Polarization by Rho Proteins

Cell polarity is the asymmetric distribution of cellular and membrane components, making one side of the cell different from the other. This polarity is essential to many processes such as embryogenesis, axon migration, glucose transport across epithelial cells, and directional cell migration. A migrating cell responds to intracellular or extracellular signals via molecular cascades that reorganize the actin cytoskeleton to establish this polarity. In these cells, the Rho family proteins Cdc42,...
Activation and Inactivation of G Proteins01:22

Activation and Inactivation of G Proteins

Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...

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Detection of Small GTPase Prenylation and GTP Binding Using Membrane Fractionation and GTPase-linked Immunosorbent Assay
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A Rho GTPase signal treadmill backs a contractile array.

Brian M Burkel1, Helene A Benink, Emily M Vaughan

  • 1Department of Zoology, University of Wisconsin-Madison, 1525 Linden Drive, Madison, WI 53706, USA.

Developmental Cell
|July 24, 2012
PubMed
Summary

Cellular wound repair involves contractile arrays powered by actin filaments and myosin-2. Directional Rho GTPase gradients, not just contraction, drive array movement and closure.

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Detection of Small GTPase Prenylation and GTP Binding Using Membrane Fractionation and GTPase-linked Immunosorbent Assay
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RhoC GTPase Activation Assay
09:58

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Published on: August 22, 2010

Area of Science:

  • Cell biology
  • Cytoskeletal dynamics
  • Wound healing mechanisms

Background:

  • Contractile arrays of actin filaments (F-actin) and myosin-2 are crucial for cellular processes.
  • Rho GTPases, specifically Rho and Cdc42, stimulate contractile array formation.
  • Array movement was traditionally attributed to contraction itself post-assembly.

Purpose of the Study:

  • To investigate the mechanisms of contractile array movement during cellular wound repair.
  • To analyze the relationship between GTPase activity and array dynamics.
  • To determine the role of contraction versus GTPase signaling in array closure and translocation.

Main Methods:

  • Analysis of contractile array movement and Rho/Cdc42 GTPase activity during cellular wound repair.
  • Experimental suppression of contraction to observe its effect on F-actin and myosin-2 translocation.
  • Observation of array and zone closure dynamics under inhibited contraction.

Main Results:

  • Suppression of contraction prevented F-actin and myosin-2 translocation but not array or zone closure.
  • Array and zone closure are driven by a "signal treadmill" of GTPase activation and loss.
  • This treadmill requires myosin-2-powered contraction and F-actin turnover for organization.

Conclusions:

  • Directional gradients in Rho GTPase turnover provide directional information to contractile arrays.
  • Myosin-2-powered contraction and F-actin turnover are essential for the proper functioning of these GTPase gradients.
  • Contractile array movement is regulated by a signaling mechanism distinct from simple mechanical contraction.