M-Sec promotes membrane nanotube formation by interacting with Ral and the exocyst complex


Cell–cell communication is essential for the development and homeostasis of multicellular organisms. Recently, a new type of cell–cell communication was discovered that is based on the formation of thin membranous nanotubes between remote cells1,2. These long membrane tethers, termed tunneling nanotubes (TNTs), form an intercellular conduit and have been shown to enable the transport of various cellular components and signals. However, the molecular basis for TNT formation remains to be elucidated. Here we report that a mammalian protein, M-Sec, induces de novo formation of numerous membrane protrusions extending from the plasma membrane, some of which tether onto adjacent cells and subsequently form TNT-like structures. Depletion of M-Sec by RNA interference (RNAi) greatly reduced endogenous TNT formation as well as intercellular propagation of a calcium flux in a macrophage cell line. Furthermore, blockage of the interaction of M-Sec with Ral and the exocyst complex, which serves as a downstream effector of Ral, attenuated the formation of membrane nanotubes. Our results reveal that M-Sec functions as a key regulator of membrane nanotube formation through interaction with the Ral–exocyst pathway.

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Figure 1: M-Sec is important for endogenous TNT formation by Raw264.7 macrophages.
Figure 2: M-Sec induces F-actin-containing membrane protrusions.
Figure 3: Intercellular calcium signalling between remote cells is observed only in physically connected cell pairs.
Figure 4: Involvement of small GTPases in M-Sec-stimulated TNT formation.
Figure 5: Involvement of the exocyst complex in M-Sec-induced TNT formation.


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We would like to thank I. Yamashita and Y. Fujimura for technical assistance, and. P. Burrows and C. Blaumueller for critically reviewing the manuscript. This study was supported in part by Grants-in-Aid for Young Scientists (B) (K.H.), Scientific Research (B) (H.O.), Scientific Research in Priority Areas (H.O. and K.H.) and Scientific Research on Innovative Areas (H.O.) from the Ministry of Education, Culture, Sports, Science and Technology of Japan, and grants from the National Institutes of Health (GM067002; C.Y.) and the Takeda Science Foundation (K.H.).

Author information

K.H. designed and performed experiments, and wrote the paper. S.Ki. performed experiments and helped with data analysis. H.T., M.O., S.Ka., H.K., M.I. and H.W. helped with the experiments. C.Y. and C.C.H. prepared antibodies and performed experiments. H.O. supervised the project and wrote the paper with K.H.

Correspondence to Hiroshi Ohno.

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Hase, K., Kimura, S., Takatsu, H. et al. M-Sec promotes membrane nanotube formation by interacting with Ral and the exocyst complex. Nat Cell Biol 11, 1427–1432 (2009). https://doi.org/10.1038/ncb1990

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