Exploring The Transport Mechanism Of Membrane Nanotubes And The Associated Infection Behavior Of Virus By Quantum Dots-based Single-Particle Tracking

Membrane nanotubes, as recently discovered long-range connections between cells, have been identified between various cell types. These tubular structures arouse strong interest due to their ability to provide a channel for intercellular communication, signaling and the spread of pathogens. Exploring the transport mechanism of membrane nanotubes may contribute to a better understanding of cell-to-cell communication. Avian influenza viruses are a potential and enormous threat to public health for causing recurrent epidemics and occasional pandemics. A systematic study of infection mechanism of avian influenza virus and transfer of virus along membrane nanotubes not only help to enrich the knowledge on cross-species transmission, but also can facilitate possible prophylactic and treatment of viral diseases.Single-particle tracking (SPT) technique is a powerful tool to study in-situ dynamics of single particle or single molecular in real time, which is widely used in the biomedical field. Quantum dots (QDs) possess unique fluorescent properties such as high brightness and excellent photostability, which is very suitable for long-time SPT. In this work, we study the transportation of membrane nanotubes and infection of avian influenza virus by QDs-based SPT.The main research works in this dissertation are as follows:(1) The transport mechanism of membrane nanotubes was revealed by QDs-based SPT. We monitored the transport process of quantum dots-labeled wheat germ agglutinin (QDs-WGA) and dissected the transport behaviors of QDs-WGA in nanotubes between cancer cells. We found that membrane nanotubes allow effective transport of QDs-WGA. The transport of QDs-WGA in membrane nanotubes is driven by myosin motors in an active and unidirectional manner. These results provide a better understanding of cell-to-cell communication for cancer research.(2) We investigated the membrane nanotube-related infection behavior of the avian influenza H9N2virus by QDs-based SPT. We studied the influence of H9N2virus infection on the forms and constructions of membrane nanotube of Vero cells and found that the virus infection process can induce the formation of the membrane nanotubes. Then, we monitored the transport behavior of QDs-labeled influenza virus along the membrane nanotubes by SPT, and found that the transport is a slow and undirected process. This work revealed the membrane nanotube-related intercellular infection process of influenza virus, which provides the theoretical basis for further exploring the infection mechanisms of avian infection virus between human cells.(3) We studied the infection mechanism of avian influenza H9N2virus in human bronchial epithelial (HBE) cells and transport behavior of the virus between the cells by QDs-based SPT. We examined the viral infection process in individual living HBE cells and investigated the infection behavior of individual viruses. By analyzing the transport process of sialic acid receptors, we found the transport process of sialic acid receptors is quite similar to that of virus, indicating that the infection behavior of H9N2virus complied with the transport behavior of sialic acid receptors in living cells. By tracking the transport behavior of the virus along the membrane nanotube of HBE cells, we found that the transport process is slow in a directed manner, similar to that along the membrane nanotube of Vero cells. This provided dynamic evidence of sialic acid receptors-related infection behavior of avian influenza virus in live cells by real-time SPT. The results may contribute to a new insight of the cross-species transmission of avian influenza virus.