Obstructions Inhibit Long-range Motor Motility in Microtubule Bundles

Efficient cellular transport along the cytoskeletal network is essential for cell growth and maintenance. Everything from microtubules to plasma membrane components are transported along the cytoskeletal network. Long-range transport is accomplished by molecular motors carrying cargo along a microtubule network. Recently, the role of the microtubule bundle geometry has begun to be explored. Microtubules bundle together in order to efficiently direct transport. Consequently, bundled microtubules introduce a new set of parameters which affect cellular transport, such as bundle spacing or microtubule polarity. Even previously tested parameters need to be re-considered, such as the role of obstructions. In this talk I will focus on the relationship between obstructions and microtubule polarity, and their affects on long-range transport. Microtubule polarity varies from completely uniform, with all plus-ends pointing in the same direction, to completely random. I will quantitatively show how obstructions inhibit long-range motor motility in any bundle, regardless of the distribution of microtubule polarity within the bundle. However, inhibition of long-range transport is greater in mixed polarity bundles. This result has implications for how cells use microtubule polarity to accommodate obstructions in order to efficiently direct transport.