Organization of plasma membrane functional rafts upon T cell activation

Raft microdomains have been shown to play a key role in T cell activation. We found that in human T lymphocytes the formation of functional rafts at t he plasma membrane was induced by T cell priming. In resting T cells from p eripheral blood Lck and the raft glycosphingolipid GM1 resided in intracell ular membranes. T cell activation induced synthesis of GM1 and effector cel ls showed very high levels of this lipid, which became predominantly plasma membrane associated. TCR triggering also induced targeting of the cytosoli c Lck to the plasma membrane. Thus, effector cells acquire an improved sign aling machinery by increasing the amount of rafts at the plasma membrane. T he fact that, when compared with naive T cells, memory T cells showed highe r GM1 levels suggests that raft lipid synthesis may be developmentally regu lated and tune T cell responsiveness.