Myosins play countless critical roles in the cell, each requiring it to be activated at a specific location and time. To control myosin VI with this specificity, we created an optogenetic tool for activating myosin VI by fusing the light-sensitive Avena sativa phototropin1 LOV2 domain to a peptide from Dab2 (LOVDab), a myosin VI cargo protein. Our approach harnesses the native targeting and activation mechanism of myosin VI, allowing direct inferences on myosin VI function. LOVDab robustly recruits human full-length myosin VI to various organelles in vivo and hinders peroxisome motion in a lightcontrollable manner. LOVDab also activates myosin VI in an in vitro gliding filament assay. Our data suggest that protein and lipid cargoes cooperate to activate myosin VI, allowing myosin VI to integrate Ca
2+, lipid, and protein cargo signals in the cell to deploy in a site-specific manner.otor proteins play countless roles in biology, each requiring the motor to be recruited and activated at a particular time and place inside the cell. To dissect these multiple roles, we must develop tools that allow us to control the recruitment and activation process. One promising technique for achieving this goal is through optogenetics (1). Optogenetics involves the engineering and application of optically controlled, genetically encoded proteins and is transforming the fields of neuro-and cell biology (2, 3). A major benefit of optogenetics is that proteins are activated using light, which allows for high temporal and spatial control over a protein of interest.Myosin VI is a motor protein whose study could particularly benefit from optogenetic control. It is the only myosin known to walk toward the pointed end of actin filaments (4, 5). This property enables it to perform a diverse array of cellular functions, including cell division, endosome trafficking, autophagy, and Golgi and plasma membrane anchoring (6-9). Myosin VI is also autoinhibited, a property that is commonly found in other myosins (10). When myosin VI binds to cargo through specialized adaptor proteins, this autoinhibition is relieved through a poorly understood mechanism likely involving the disruption of an interaction between its cargo binding domain (CBD) and the myosin head (11,12). Dissociation of the CBD from the head both frees the head to bind tightly to actin and exposes dimerization sites throughout the tail domain of myosin VI, allowing it to become a processive dimer (13-15). In some cases, myosin VI could conceivably function as a monomer, for example when fulfilling its role as a membrane tether during spermatid individualization (16). If this is the case, more work is needed to elucidate the cellular signals that determine its oligomeric state at each site of action.Myosin VI has two classes of cargo proteins that bind to distinct, conserved motifs on the myosin VI C terminus (17). Disabled2, or Dab2, belongs to the class of cargo proteins that bind to a conserved WWY site on myosin (18). Optineurin (OPTN) is a member of the second class that binds ...