A conformational change within the WAVE2 complex regulates its degradation following cellular activation

Area of Science:

• Cell Biology
• Molecular Biology
• Immunology

Background:

• Wiskott-Aldrich syndrome protein family Verprolin-homologous protein-2 (WAVE2) is crucial for actin cytoskeleton regulation.
• WAVE2 functions within the pentameric WAVE regulatory complex (WRC) to promote actin polymerization via the Arp2/3 complex.
• Mechanisms of WAVE2's negative regulation, particularly during cellular activation, remain largely uncharacterized.

Purpose of the Study:

• To investigate the post-translational modification and degradation of WAVE2 in response to T-cell activation.
• To identify the specific site of WAVE2 ubiquitylation and its functional consequences.
• To elucidate the role of WRC conformation in regulating WAVE2 stability and degradation.

Main Methods:

• T-cell activation assays
• Ubiquitylation analysis
• Proteasomal degradation assays
• Site-directed mutagenesis to map ubiquitylation sites
• Förster resonance energy transfer (FRET) to study protein complex conformation

Main Results:

• WAVE2 undergoes ubiquitylation and subsequent proteasomal degradation in a T-cell activation-dependent manner.
• Lysine 45 (K45) at the N-terminus of WAVE2 was identified as the primary ubiquitylation site.
• The autoinhibitory conformation of the WRC stabilizes WAVE2 in resting cells; T-cell activation releases this inhibition, exposing WAVE2 to ubiquitylation and degradation.
• Conformational changes in WAVE2 during cellular activation directly influence its degradation pathway.

Conclusions:

• T-cell activation triggers a regulatory cascade involving WAVE2 ubiquitylation and degradation, impacting actin dynamics.
• The conformational state of the WRC is critical for controlling WAVE2 stability and its availability for signaling.
• Understanding WAVE2 regulation provides insights into immune cell activation and actin cytoskeleton control.