Electron microscopic imaging of Ras signaling domains.

Ras isoform-specific signaling from the plasma membrane appears to be regulated by interactions with distinct functional microdomains. We have developed protocols allowing the generation of 2-D spatial maps describing cell surface microdomain distributions. The combined electron microscopic (EM)-statistics approach provides nanometer scale resolution allowing both inner and outer leaflet domains to be visualized and cross-correlated with each other or with a protein of interest. In particular, the technique has allowed the interaction of Ras isoforms with signaling microdomains and proteins regulating these compartments to be screened. By allowing detailed monitoring of cell surface organization and compartmentalization, the approach has widespread potential for studies of plasma membrane-dependent cell biology, including regulated signaling and membrane trafficking.