Precise package delivery in cells?

Cells transport materials efficiently through intracellular vesicles called endosomes^[2]. Materials are transported to their destination by motor proteins that move along a complex network of microtubules. Observing the movement and rotation of endosomes appearing in the transport process provides important information for understanding how intracellular transport is efficiently regulated, which in turn helps elucidate cell functions and diseases.

To visualize this transport process, the research team developed FT-pdf microscopy that performs analysis with the Fourier transform^[3] technique using nanoparticles that have "polar angle dependence"^[4]. Images of the scattering signals observed by rotating polarized light are continuously captured over a long period of time, and when combined with existing single-particle tracking technology, the movement and rotation of particles can be observed in real time.

Using a plasmonic dark-field microscope, the research team discovered temporal patterns (high time-series characteristics) in the rotational movements of endosomes in cells, which they interpreted as similar to the reinforcement learning strategy of navigation robots or internet search engines. The real-time strategy of endosome transport can be analyzed and applied to disease cell models to explain and diagnose the cause of diseases.

"As shown in this study, ordinary cells that make up the human body seem to be equipped with the data learning technology of robots that humans are actively developing," said Prof. Seo of the Department of Chemical Physics at DGIST. "This molecular-level strategy holds the key to precise material transport and is another research topic. Our research result is expected to contribute to the understanding and diagnosis of diseases in the future through its application to diseased cells," Prof. Seo added.

The research was supported by the Ministry of Science and ICT and the National Research Foundation of Korea's Basic Research Program and Engineering Research Center (ERC) Program, DGIST's Grand Challenge Research Innovation Project (D-GRIP), and HRHR+ Program. The research results were published in the international journal Advanced Science.

Notes:

^[1] Motor proteins: molecular motors that move along the microtubules in cells. They include myosin and kinesin.

^[2] Endosome: vesicles formed in the cytoplasm by endocytosis, etc. in a cell.

^[3] Fourier transform: a mathematical tool that decomposes a function of time or space into its various frequency components and allows analysis of the magnitude and phase for each frequency.

^[4] Polar angle dependence: refers to the phenomenon where the nature of the interaction of a polarized state of light with matter changes with the polar angle of the light.