Kinesin-1 Autoinhibition Tunes Cargo Transport by Motor Ensembles
Abstract
Intracellular vesicular transport by kinesin-1 motors through numerous 3-dimensional (3D) microtubule (MT) intersections must be regulated to support proper vesicle delivery. Knowing kinesin-1 can be regulated via autoinhibition, does kinesin-1 exhibit autoinhibition on cargo, and could this regulate vesicular transport through 3D MT intersectionsin vitro? To answer this question, we compared liposome transport by ∼10 nearly full-length kinesin-1 motors with KLC bound (KinΔC) versus constitutively active control (K543). In 3D MT intersections, KinΔC-liposomes terminate (48%), go straight (43%), but rarely turn (9%), starkly contrasting K543-liposomes which go straight (57%), turn (31%), but rarely terminate (12%). On single MTs, KinΔC-liposomes have reduced run lengths and detachment forces versus K543-liposomes, suggesting autoinhibition reduces MT engagement, as supported by 3-fold lower KinΔC MT landing rates versus K543, and mechanisticin silicomodeling. Furthermore, kinesore, a small molecule that overcomes kinesin-1 autoinhibition, restores KinΔC’s MT engagement. Thus, we propose that partial kinesin-1 autoinhibition while cargo-bound may fine-tune cargo delivery to support physiological demands.
Statement of significance
Kinesin-1 vesicular transport through the cell’s complex microtubule (MT) network must be spatially and temporally regulated to meet the cell’s physiological demands. With kinesin-1 being autoinhibited, does this form of regulation impact the directional outcomes of vesicles encountering 3-dimensional (3D) MT-MT intersections as they do in cells? To address this in vitro, liposomes transported by kinesin-1 motors (team of ∼10), which exhibit autoinhibition, are challenged with 3D MT intersections and interestingly, preferentially terminate or go straight and rarely turn, while liposomes transported by constitutively active motors preferentially go straight or turn but rarely terminate. Therefore, autoinhibition reduces the number of MT-engaged motors within the team and provides the cell a means of fine-tuning cargo transport to its destination.
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