UC Berkeley

Cytoskeletal motors play essential roles in controlling both the internal organization and divisionof eukaryotic cells. Much of this organization is maintained through the precise trafficking and delivery of intracellular components to specific destinations within the cell. Intracellular transport is driven by motor proteins that move unidirectionally along cytoskeletal filaments. Although the mechanisms of motor stepping and motility have been well studied, it remains unclear how motors are correctly coupled to their cargoes and how this information is transmitted to direct the cargo to its proper destination.

In my doctoral work, I studied how the activity of dynein and kinesin are regulated by specificadaptor proteins that link these motors to intracellular cargoes. I showed that different cargo adaptor proteins can tune dynein force generation and velocity by recruiting multiple motors to the same complex. Furthermore, I discovered that cargo adaptors adjust dynein’s force generation and velocity through separate mechanisms. While cargo adaptors control force generation by modulating motor stoichiometry, velocity is altered through allosteric interactions that increase the enzymatic activity of dynein’s motor domain.

In addition, I studied how both kinesin and dynein regulate the transport and directionality ofmitochondria. I used an in vitro reconstitution approach to determine how mitochondrialassociated proteins interact with both dynein and kinesin. Interestingly, I discovered that two proteins, TRAK1 and TRAK2, are activating cargo adaptors that are sufficient to induce dynein’s processive motility. Furthermore, I found that TRAK1 and TRAK2 can also bind to kinesin, suggesting that they may act as scaffolds to bridge both motors together. In summary, this study provides mechanistic detail into the motor transport complex that drives bidirectional mitochondrial transport.