TRAK adaptors regulate the recruitment and activation of dynein and kinesin in mitochondrial transport
John T. Canty, Andrew Hensley, Merve Aslan, Amanda Jack, Ahmet Yıldız
Abstract
Abstract Mitochondrial transport along microtubules is mediated by Miro1 and TRAK adaptors that recruit kinesin-1 and dynein-dynactin. To understand how these opposing motors are regulated during mitochondrial transport, we reconstitute the bidirectional transport of Miro1/TRAK along microtubules in vitro. We show that the coiled-coil domain of TRAK activates dynein-dynactin and enhances the motility of kinesin-1 activated by its cofactor MAP7. We find that TRAK adaptors that recruit both motors move towards kinesin-1’s direction, whereas kinesin-1 is excluded from binding TRAK transported by dynein-dynactin, avoiding motor tug-of-war. We also test the predictions of the models that explain how mitochondrial transport stalls in regions with elevated Ca 2+ . Transport of Miro1/TRAK by kinesin-1 is not affected by Ca 2+ . Instead, we demonstrate that the microtubule docking protein syntaphilin induces resistive forces that stall kinesin-1 and dynein-driven motility. Our results suggest that mitochondrial transport stalls by Ca 2+ -mediated recruitment of syntaphilin to the mitochondrial membrane, not by disruption of the transport machinery.