Reporting Rotational Dynamics of Intracellular Cargos with Janus Particles

Intracellular cargo transport is an essential process underlying a multitude of cellular functions. Dysfunctional cargo transport is associated with various human diseases such as amyotrophic lateral sclerosis (ALS) and Alzheimer's disease. This highlights the critical need for understanding the regulatory mechanism of cargo transport. Extensive efforts have been focused on interpreting the cargo transport and function of motor proteins based on the translational movement of cargos. In contrast, the rotation of cargos has been rarely studied and poorly understood, even though the tug-of-war between motor proteins is predicted theoretically to cause rotation of cargos. Our limited knowledge about the cargo rotation is due to the lack of method to directly measure cargo rotation in vivo. I will show, in this presentation, our recent progress towards addressing this critical need. By designing a novel type of optically anisotropic particles as the rotational probe, we are now able to visualize the transport and rotation of cargos in living cells with high spatial and temporal resolutions. Our results demonstrate that the cargo rotation is not only a simple act from the tug-of-war of motor proteins, but is also influenced by the intracellular environment.