Orientation-dependent CD45 inhibition with viral and engineered ligands

Area of Science:

• Immunology
• Structural Biology
• Virology

Background:

• CD45 (Cluster of Differentiation 45) is a crucial cell surface phosphatase regulating T cell receptor signaling thresholds.
• Despite its importance, CD45 lacks a known endogenous ligand, making its regulation complex.
• Adenovirus E3/49K protein evades host immunity by targeting the extracellular domain of CD45.

Purpose of the Study:

• To elucidate the structural mechanism by which adenovirus E3/49K interacts with CD45.
• To explore the potential for engineering novel CD45 ligands to modulate T cell responses.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine the structure of the CD45-E3/49K complex.
• Protein engineering to design and create CD45 surrogate ligands.

Main Results:

• The E3/49K protein forms a 'beads on a string' structure, inducing CD45 dimerization via its D3 domain.
• This dimerization leads to steric inhibition of CD45's intracellular phosphatase activity.
• Engineered CD45 ligands demonstrated the ability to fine-tune T cell activation by controlling CD45 dimer orientation and proximity.

Conclusions:

• Adenovirus E3/49K provides a structural basis for understanding CD45 ligand-mediated regulation.
• Extracellular ligands can modulate CD45 activity and T cell responses by inducing specific dimerization patterns.
• Engineered CD45 ligands offer a novel strategy for therapeutic intervention in T cell-mediated immunity.