Fig. 4

Illustrations of TNT formation models. On the left side, the formation of a nanotube by the actin-driven growth of membrane protrusions is shown. a) The protrusion from one cell elongates until it reaches the target cell, where physical contact will be established by adhesion followed by a membrane fusion of tunnel and target cell. An open-ended nanotube connection will be generated. b) It might also be possible that two different membrane protrusions meet each other and establish a connection by adhesion and fusion. c) On the right side, the second formation model is illustrated, the TNT formation by cell dislodgement. Here, the cells migrate apart from each other after physical contact and during their migration the nanotunnel will be pulled out of the cells. At the end of the migration, the cells are still connected via the generated TNT