Rapid Rerouting of Myosin Traffic at the T Cell Immunological Synapse

Cytoskeletal motors travel in patterns set by the architecture of their tracks. Nevertheless, we have a limited understanding of how cells dynamically reorganize their traffic patterns in response to signaling events. To investigate cytoskeletal motor rerouting, we used T cells as a model system. Upon an encounter between a T cell and an antigen presenting cell, the T cell builds a specialized interface with spatially organized immunoreceptors and adhesion molecules called the immunological synapse (IS). The IS also constructs new actin networks within minutes that define the synaptic structure. Here we track the movements of single myosin motors along presynaptic and synaptic actin networks of the T cell. We find that both myosin-5 and myosin-6 reroute after IS construction. For example, most myosin-5 traffic moves inward at the IS, although most of the IS actin filaments have a barbed end out orientation. This anomalous myosin-5 traffic pattern indicates that the IS makes two types of actin networks: a structural network that controls IS shape, and a distinct trafficking network that supports myosin motility. We disrupt these trafficking networks with chemical probes against actin, which inhibits the appearance of cell surface markers of T cell activation. Our results highlight the importance of the sparse actin networks at the center of the IS in T cell function.