Controversy and consensus regarding myosin II function at the immunological synapse

• F-actin and myosin II form arcs at the immunological synapse.
• IS domains correspond to the lamellipodium and lamellum of other cells.
• Researchers disagree about the magnitude of myosin II's role in IS formation and T cell signaling.
• The magnitude of myosin II's contribution may be context dependent.

Regulated actin dynamics play a central role in modulating signaling events at the immunological synapse (IS). Polymerization of actin filaments at the periphery of the IS, coupled to depolymerization near the center, generates a centripetal flow of the actin network and associated movement of signaling molecules. A recent flurry of papers addresses the role of myosin II in facilitating these events. Investigators agree that myosin II is present at the IS, where it forms actomyosin arcs within the peripheral supramolecular activation cluster, a region corresponding to the lamellum of migrating cells. However, there is substantial disagreement about the extent to which myosin II drives IS formation and signaling events leading to T cell activation.