The dynein cortical anchor Num1 activates dynein motility by relieving Pac1/LIS1-mediated inhibition.
Cortically anchored dynein orients the spindle through interactions with astral microtubules. In budding yeast, dynein is offloaded to Num1 receptors from microtubule plus ends. Rather than walking toward minus ends, dynein remains associated with plus ends due in part to its association with Pac1/LIS1, an inhibitor of dynein motility. The mechanism by which dynein is switched from "off" at the plus ends to "on" at the cell cortex remains unknown. Here, we show that overexpression of the coiled-coil domain of Num1 specifically depletes dynein-dynactin-Pac1/LIS1 complexes from microtubule plus ends and reduces dynein-Pac1/LIS1 colocalization. Depletion of dynein from plus ends requires its microtubule-binding domain, suggesting that motility is required. An enhanced Pac1/LIS1 affinity mutant of dynein or overexpression of Pac1/LIS1 rescues dynein plus end depletion. Live-cell imaging reveals minus end-directed dynein-dynactin motility along microtubules upon overexpression of the coiled-coil domain of Num1, an event that is not observed in wild-type cells. Our findings indicate that dynein activity is directly switched "on" by Num1, which induces Pac1/LIS1 removal.
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523.
Lindsay G
LG
Lammers
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523 steven.markus@colostate.edu.
Steven M
SM
Markus
D002352:Carrier Proteins / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004398:Dyneins / Q000378:metabolism*; D004722:Endoribonucleases / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism
D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; C071961:NUM1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D004722:Endoribonucleases; C499539:PAC1 protein, S cerevisiae; D004398:Dyneins