Synergy between Membrane Topography and Domains to Control Signaling Protein Localization in Mast Cells Facilitates...

Area of Science:

• Immunology
• Cell Biology
• Biophysics

Background:

• Mast cell surfaces feature microvilli, similar to T and B cells.
• Signaling proteins crucial for mast cell activation are known to localize to these microvilli.
• The relationship between ordered lipid nanodomains and membrane topography in mast cells remained unclear.

Purpose of the Study:

• To investigate the topographical organization of signaling proteins and lipid nanodomains on mast cell surfaces.
• To determine how membrane structure influences mast cell activation upon antigen stimulation.
• To elucidate the role of ordered lipid nanodomains and actin-binding proteins in mast cell signaling.

Main Methods:

• Microvillar cartography (MC) for nanoscale imaging of mast cell surfaces.
• Scanning Electron Microscopy (SEM) and co-localization probability (CP) analysis.
• Selective lipid probes and flow cytometry to study lipid environments and protein distribution.

Main Results:

• Resting mast cells show FcεRI and Lyn kinase localized to separate nano-assemblies on microvilli.
• Antigen activation leads to the merging of these proteins with LAT on elongated microvilli and ruffles.
• Ordered lipid nanodomains are preferentially found on microvilli, while disordered lipids are on flatter regions.
• Disruption of ordered lipid regions impairs signaling protein localization, highlighting the role of lipid-protein interactions.

Conclusions:

• Mast cell microvilli serve as platforms for organizing signaling proteins and ordered lipid nanodomains, enhancing antigen sensitivity.
• The interplay between ordered lipid nanodomains and actin-associated proteins (ERM, cofilin) drives the selective localization of signaling components.
• This topographical organization primes mast cells for rapid and efficient immune responses upon stimulation.