Cross talk between CD3 and CD28 is spatially modulated by protein lateral mobility

Area of Science:

• Immunology
• Cell Biology
• Biophysics

Background:

• T-cell activation requires coordinated signaling from the T-cell receptor (TCR) and CD28 costimulatory receptor.
• The spatial organization of these receptors within the immune synapse influences T-cell signaling, but this impact is not fully understood.

Purpose of the Study:

• To investigate how the spatial arrangement of CD3 and CD28 ligands on micropatterned surfaces affects T-cell activation and signaling.
• To elucidate the role of Lck kinase dynamics and the actin cytoskeleton in T-cell costimulation.

Main Methods:

• Utilized micropatterned surfaces presenting controlled arrangements of CD3 and CD28 ligands.
• Studied primary human and mouse CD4(+) T cells.
• Analyzed the localization and diffusion of phosphorylated Lck.
• Investigated the effect of actin cytoskeleton disruption on T-cell signaling.

Main Results:

• Functional convergence of CD3 and CD28 signaling was impaired when ligands were spatially separated by micrometer distances.
• Phosphorylated Lck concentrated at CD3 engagement sites with limited mobility, suggesting a reaction-diffusion mechanism.
• Disrupting the actin cytoskeleton enhanced Lck mobility and restored costimulation with spatially separated ligands in human T cells.
• Reduced membrane mobility in mouse T cells increased sensitivity to CD3-CD28 separation.

Conclusions:

• T-cell activation is sensitive to the microscale spatial organization of extracellular ligands.
• A subcellular reaction-diffusion system involving Lck kinase and the actin cytoskeleton regulates T-cell costimulation based on spatial cues.