Nanodomains in early and later phases of FcεRI signalling

Our long-term efforts to elucidate receptor-mediated signalling in immune cells, particularly transmembrane signalling initiated by FcεRI, the receptor for IgE in mast cells, led us unavoidably to contemplate the role of the heterogeneous plasma membrane. Our early investigations with fluorescence microscopy revealed co-redistribution of certain lipids and signalling components with anti-gen-cross-linked IgE–FcεRI and pointed to participation of ordered membrane domains in the signalling process. With a focus on this function, we have worked along with others to develop diverse and increasingly sophisticated tools to ana-lyse the complexity of membrane structure that facilitates regulation and targeting of signalling events. The present chapter describes how initial membrane interac-tions of clustered IgE–FcεRI lead to downstream cellular responses and how bio-chemical information integrated with nanoscale resolution spectroscopy and imaging is providing mechanistic insights at the level of molecular complexes. Keywords: electrostatic association, exocytosis, IgE receptor (FcεRI), mast cell, phosphoinositide-dependent signalling, receptor immobilization and clustering, store-operated Ca2+ entry, syntaxin