Structural basis of PSGL-1 binding to ERM proteins

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• P-selectin glycoprotein ligand-1 (PSGL-1) is crucial for leukocyte inflammatory responses.
• Ezrin-radixin-moesin (ERM) proteins regulate PSGL-1 localization on cell surfaces during activation.
• ERM proteins typically bind adhesion molecules via a conserved Motif-1, which PSGL-1 lacks.

Purpose of the Study:

• To elucidate the structural basis of the interaction between PSGL-1 and the radixin FERM domain.
• To understand how PSGL-1 binds ERM proteins in the absence of the canonical Motif-1.

Main Methods:

• Crystal structure determination of the complex between the radixin FERM domain and a PSGL-1 juxtamembrane peptide.
• Analysis of protein-protein interactions and binding interfaces.

Main Results:

• The PSGL-1 peptide binds the radixin FERM domain's subdomain C groove, forming a beta-strand and a solvent-exposed loop.
• PSGL-1 lacks the Motif-1 3(10) helix due to the absence of a critical alanine residue.
• Non-conserved residues Met9 and His8 in PSGL-1 stabilize the peptide conformation and enhance binding to the FERM domain groove.

Conclusions:

• Non-conserved residues play a significant role in compensating for the lack of conserved binding residues in PSGL-1.
• This structural insight clarifies the binding mechanism of PSGL-1 to ERM proteins, important for inflammatory cell adhesion.