Merging complexes: properties of membrane raft assembly during lymphocyte signaling

In the lipid raft model, cell membranes contain detergent-resistant membrane domains, or rafts, that function in cell signaling. Recent findings have shown rafts are assembled to form macrodomains that are micrometers in diameter, one example of which is the immune synapse in stimulated lymphocytes. Because immune synapses are necessary for lymphocyte activation, deciphering the mechanism of their assembly has been an active topic of research. A current model, in which macrodomains are formed and maintained through association of rafts with the actin cytoskeleton, is discussed here. Recent evidence that either supports or challenges this model is presented, as well as data suggesting that macrodomain assembly might act as a gatekeeper to lymphocyte signaling and functioning.