T cell synapse assembly: proteins, motors and the underlying cell biology.

A tantalizing feature of the 'immunological synapse' is the segregation of transmembrane proteins into activating clusters and their underlying signalosomes. The mechanisms by which transmembrane proteins are initially recruited to and then stably segregated at the synapse remains an outstanding question in the field; and one likely to reveal key modes of signaling regulation. Ongoing real-time imaging approaches and a refocusing of efforts upon understanding the basic cell biology of T cells have all contributed to a developing model of T cell behavior; elementary TCR-derived signaling quickly feeds back into the basic cellular programs controlling cell shape, adhesiveness, motility, as well as some poorly understood aspects of membrane fluidity and segregation. It is increasingly clear that the mechanisms for control at this level are shared between T cells and other cell types and may not be revealed in differential genomic screening. To this end, imaging-based genetic screens are now coming online to aid in identifying the ubiquitous proteins that function at polarized signaling surfaces.