"Tunneling nanotubes (TNTs), recently discovered thin membrane channels connecting distant cells, represent the underlying structure of a previously unrecognized type of cell-to-cell communication. To date, a growing number of cell types have been found to use TNTs for the intercellular exchange of diverse cargoes ranging from cytoplasmic signalling molecules such as calcium ions to small vesicles of endocytic origin. During the past year, pathogens such as the human immunodeficiency virus and prions were also found to spread TNT-dependently between cells. Given the emerging wide range of implications of TNTs in the field of biomedical research, it is important to first learn the basic principles and mechanisms of TNT-dependent cell-to-cell interactions. I therefore propose to focus on three major questions: First, I will characterize the type of endocytic vesicles transiting through TNTs using flow cytometry and quantitative live cell imaging to monitor the transfer of endosomal markers (Rab GTPases) through TNTs. Secondly, using the same methodological approach, I will analyze which myosin motor(s) is (are) involved in the active transport of vesicles through TNTs. Third, by employing a proteomic screen assay, I aim at characterizing the entire set of proteins/signalling molecules transferred through TNTs."