Membranous structures transfer cell surface proteins across NK cell immune synapses

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Intercellular transfer of cell surface proteins is a key mechanism for immune cell communication.
• Natural killer (NK) cell receptor KIR2DL1 and its ligand HLA-C are prototypical examples of proteins exchanged between cells.

Purpose of the Study:

• To investigate the molecular mechanisms underlying the intercellular exchange of KIR2DL1 and HLA-C.
• To elucidate the role of cell contact, receptor-ligand interactions, and signaling in protein transfer.

Main Methods:

• Utilized fluorescence microscopy to track protein localization on recipient cells.
• Employed scanning and transmission electron microscopy to visualize protein location and membrane structures at the immune synapse.
• Investigated transfer dependence on KIR2DL1 signaling and cognate interactions.

Main Results:

• Protein transfer was contact-dependent and enhanced by cognate receptor-ligand pairs (KIR2DL1/HLA-C), but independent of KIR2DL1 signaling.
• Transferred proteins localized to discrete membrane structures within the immunological synapse.
• Membrane protrusions were identified interacting between cells at the synapse, suggesting a transfer mechanism.

Conclusions:

• Intercellular protein transfer is mediated by membrane protrusions within and surrounding the immunological synapse.
• This mechanism facilitates immune cell communication through the exchange of surface proteins like KIR2DL1 and HLA-C.