How is Motor-Driven Transport Regulated?

Organelle transport in vivo requires that motors move specific cargoes at precise times to the correct destinations. The underlying mechanisms remain largely mysterious, but likely act at many different levels. The cartoon below conceptualizes several possiblities: adapters that dock particular motors to specific cargoes, switches that turn motors on or off, coordinators that prevent interference between opposing motors, and trans-acting signaling molecules that integrate motor activity with other cellular events.



Many important questions remain unresolved, such as:

• How does motor activity respond to extracellular signals and developmental cues?
• If a single cargo carries several copies of the same type of motor, do these motors act independently of each other or is their activity coordinated?
• If a single cargo carries different kinds of motors, for different directions of motion (e.g. dynein and kinesin) or different tracks (e.g. kinesin and myosin), why do they not simply interfere with each other, causing motion to cease?
• The cell contains many different kinds of motors and cargoes. How do the correct ones link up?
• Sometimes, the same type of motor is involved in moving various cargoes, yet transport characteristics differ between these cargoes.  How can transport be cargo-specific?