Related Experiment Video

Updated: Aug 8, 2026

Aip1p Dynamics Are Altered by the R256H Mutation in Actin
08:57

Aip1p Dynamics Are Altered by the R256H Mutation in Actin

Published on: July 30, 2014

RAC regulation of actin polymerization and proliferation by a pathway distinct from Jun kinase

T Joneson1, M McDonough, D Bar-Sagi

  • 1Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook, NY 11794, USA.

Science (New York, N.Y.)
|November 22, 1996
PubMed

Insights

RAC proteins control cell growth and movement through distinct pathways. Mutants revealed that RAC

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • RAC guanine nucleotide binding proteins are key regulators of cellular processes.
  • These processes include actin polymerization, JNK cascade activation, and cell proliferation.

Purpose of the Study:

  • To investigate the distinct effector pathways of RAC proteins.
  • To understand how RAC regulates actin polymerization, JNK activation, and cell proliferation.

Main Methods:

  • Creation and analysis of RAC effector loop mutants.
  • Assessment of mutant binding affinities to downstream effectors like PAK3 and POR1.
  • Evaluation of mutant-induced cellular responses, including JNK activity, membrane ruffling, and transformation.

Main Results:

  • RACV12H40 mutant, defective in PAK3 binding but not POR1 binding, failed to activate PAK/JNK but induced membrane ruffling and transformation.
  • RACV12L37 mutant, binding PAK but not POR1, activated JNK but failed to induce membrane ruffling and transformation.
  • These findings demonstrate differential RAC effector interactions.

Conclusions:

  • RAC's regulation of the JNK cascade and actin polymerization/cell proliferation involves distinct effector pathways.
  • These pathways diverge at the level of RAC protein interaction with its effectors.
  • Understanding these distinct pathways is crucial for deciphering RAC-mediated cellular signaling.

More Related Videos

A Time-Efficient Fluorescence Spectroscopy-Based Assay for Evaluating Actin Polymerization Status in Rodent and Human Brain Tissues06:54

A Time-Efficient Fluorescence Spectroscopy-Based Assay for Evaluating Actin Polymerization Status in Rodent and Human Brain Tissues

Published on: June 3, 2021

Optogenetic Inhibition of Rho1-Mediated Actomyosin Contractility Coupled with Measurement of Epithelial Tension in Drosophila Embryos12:35

Optogenetic Inhibition of Rho1-Mediated Actomyosin Contractility Coupled with Measurement of Epithelial Tension in Drosophila Embryos

Published on: April 14, 2023

Related Concept Videos

Introduction to Actin01:26

Introduction to Actin

Actin is a highly conserved cytoskeletal protein found abundantly in eukaryotic cells. It constitutes 10% weight of the total cellular protein in muscle cells, while in non-muscle cells, it is lower and makes up around 1–5 percent of the total cell protein. Actin found in the unicellular amoebae and complex multicellular animals is around 80% similar, demonstrating their conservation over a billion years of evolution.  Actin coding genes are conserved within species and across different species.
Actin Polymerization01:42

Actin Polymerization

Actin polymerization occurs through the head-to-tail association of binding sites on monomeric actin or G-actin to form filamentous or F-actin. The polymerization can be divided into three phases ̶  nucleation, elongation, and steady-state phase.
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight actin...
Generation of Straight or Branched Actin Filaments01:14

Generation of Straight or Branched Actin Filaments

The straight or branched structure formation of actin filaments is controlled by nucleating proteins such as the formins and Arp2/3 complex. Formin-mediated assembly results in straight filaments, whereas Arp2/3 protein complex-mediated assembly results in branched actin filaments.
Arp2/3 Complex
Arp2/3 complex is a seven-subunit complex consisting of two proteins similar to actin- Arp2 and Arp3, and five other subunits that help keep Arp2 and Arp3 inactive. When required, the complex is...
Actin Filament Depolymerization01:19

Actin Filament Depolymerization

Actin filaments (F-actin) are composed of actin subunits. The dissociation of actin monomers can occur from either end of F-actin. The rate of dissociation is faster from the minus-end or the pointed end, where the actin subunits exist with a bound ADP, together known as ADP-actin. The depolymerization of F-actin is aided by proteins, including the actin-depolymerizing factor (ADF) and cofilin family of proteins, gelsolin, and glia maturation factor (GMF).
In F-actin, the ADF/cofilin proteins...
Actin Polymerization and Cell Motility01:13

Actin Polymerization and Cell Motility

Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. Actin monomers polymerize to form a complex network of polarized filaments, the actin cytoskeleton, that plays a crucial role in many cellular processes, including cell motility, division, endocytosis, and metastasis of cancer cells.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
The JAK-STAT Signaling Pathway01:20

The JAK-STAT Signaling Pathway

Several cytokine receptors have tightly bound Janus kinase or JAK proteins attached at their cytosolic tail. Small signaling molecules such as cytokines, growth hormones, or prolactins bind to the cytokine receptors and initiate their dimerization. The dimerization brings the cytosolic JAKs together that trans-phosphorylate and activates each other. The activated JAKs now phosphorylate cytosolic tails of the cytokine receptors, which serve as binding sites for adaptor proteins such as  SH2...