Dynamic cortical actin remodeling by ERM proteins controls BCR microcluster organization and integrity

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Signaling microclusters are key to lymphocyte activation, but their formation mechanisms remain unclear.
• Ezrin-Radixin-Moesin (ERM) proteins connect membrane proteins to the actin cytoskeleton and influence B cell receptor (BCR) diffusion.
• ERM proteins are transiently dephosphorylated upon antigen receptor stimulation.

Purpose of the Study:

• To investigate the role of ERM proteins in the organization and integrity of BCR microclusters.
• To understand how ERM protein function affects BCR diffusion dynamics and microcluster formation.
• To elucidate the contribution of the actin cytoskeleton to B cell spreading and microcluster function.

Main Methods:

• Utilized dominant-negative and constitutively active ezrin constructs.
• Performed knockdown of ezrin and moesin expression.
• Applied chemical inhibition of actin polymerization.
• Quantitatively and qualitatively analyzed BCR microcluster formation and antigen aggregation.

Main Results:

• ERM protein inactivation led to altered BCR diffusion dynamics (transient increase followed by immobilization).
• Disruption of ERM protein function significantly changed BCR microcluster formation, antigen aggregation, and downstream signaling.
• Inhibition of actin polymerization also affected BCR microcluster structure and integrity.

Conclusions:

• ERM proteins, specifically ezrin and moesin, are critical regulators of BCR microcluster organization and integrity.
• ERM protein function and the actin cytoskeleton play essential roles in B cell spreading and microcluster dynamics.
• These findings provide new insights into the molecular mechanisms governing lymphocyte activation via BCR signaling.