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Published on: November 28, 2025
Glia maturation factor (GMF) interacts with Arp2/3 complex in a nucleotide state-dependent manner
Malgorzata Boczkowska1, Grzegorz Rebowski1, Roberto Dominguez1
1From the Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
The Journal of Biological Chemistry
|July 31, 2013
Summary
Glia maturation factor (GMF) preferentially binds to ADP-bound Arp2/3 complex, similar to other actin-depolymerizing factors. This interaction, regulated by phosphorylation, suggests GMF
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Glia maturation factor (GMF) belongs to the actin-depolymerizing factor (ADF)/cofilin family, known for regulating actin dynamics.
- While ADF/cofilin disassembles actin filaments, GMF specifically interacts with the Arp2/3 complex to promote debranching.
- ADF/cofilin exhibits higher affinity for ADP-bound actin, and its activity is modulated by phosphorylation at Ser-3.
Purpose of the Study:
- To investigate whether GMF's interaction with the Arp2/3 complex is influenced by nucleotide binding state (ATP vs. ADP) and phosphorylation.
- To determine if GMF exhibits specificity for the Arp2/3 complex over monomeric actin.
- To elucidate the role of GMF in Arp2/3 complex-mediated nucleation.
Main Methods:
- Isothermal titration calorimetry (ITC) was employed to quantify the binding affinity of GMF to ATP- and ADP-bound Arp2/3 complex.
- Site-directed mutagenesis was used to create a phosphomimetic mutant (S2E) of GMF to assess the effect of phosphorylation.
- Actin binding assays were performed to confirm GMF's specificity.
- Arp2/3 complex nucleation assays were conducted using N-WASP and WAVE2 as activators in the presence of GMF.
Main Results:
- GMF demonstrated very low affinity for ATP-bound Arp2/3 complex but bound ADP-bound Arp2/3 complex with a high affinity (0.7 μM).
- The phosphomimetic mutation S2E in GMF significantly inhibited its interaction with ADP-bound Arp2/3 complex.
- GMF did not bind monomeric actin, confirming its specificity for the Arp2/3 complex.
- GMF did not affect N-WASP-activated Arp2/3 complex nucleation but slightly inhibited WAVE2-activated nucleation at high concentrations.
Conclusions:
- GMF functions similarly to other ADF/cofilin family members, preferring ADP-bound Arp2/3 complex and being inhibited by N-terminal serine phosphorylation.
- The preference for ADP-Arp2/3 complex suggests a physiological role for GMF in debranching aged actin networks.
- GMF's mechanism likely involves debranching without significantly interfering with Arp2/3 complex nucleation, which occurs in the ATP state.
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