The myosin family: unconventional roles of actin-dependent molecular motors in immune cells

Myosins comprise a family of ATP-dependent motor proteins that are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. Recent phylogenetic analysis places myosins into 35 highly diverse classes. Although these actin-based molecular motors have been characterized extensively, and much is known about their function in different cellular compartments, there is little information available about these molecules in hematopoietic cells. The available data establish that myosins expressed by immune cells are able to support general tasks, such as maintaining plasma membrane tension, moving and secreting vesicles, aiding in endo-and exocytotic processes, and promoting the adhesion and motility of cells. Additionally, however, myosins are involved in highly specialized functions, such as regulating cell activation, IS-induced signaling, and the severing of microfilaments via the control of GTPases. In this review, we summarize the current understanding of myosins in leukocytes, with emphasis on the emerging roles of these molecular motors in immune functions. J. Leukoc. Biol. 91: 35-46; 2012.