Fig. 4

Models of mitochondrial transfer. Mitochondrial transfer can be mediated by TNTs, extracellular vesicle transport, gap junctions, and cell fusion. TNTs are normally formed from F-actin filaments. During intercellular mitochondria transfer, microtubules are also involved in TNTs and are thus able to transfer bulkier structures propelled by dynein and kinesin motor complexes consisting of several adaptor proteins, such as Miro1 or Miro2. The transfer of mitochondria via extracellular vesicles involves small double-membrane structures formed by blebbing of the plasma membrane. These vesicles can be grouped by size and mitochondrial cargo; gap junctions contain connexin structures, which form pores connecting two neighboring cells, allowing for bidirectional transport of whole mitochondria; and cell fusion allows cells to share mitochondria from the two original cell lines. During this process, several signaling pathways are triggered, resulting in increased tumorigenesis and increased metastasis of cancer cells