Exosomes and unconventional secretion

Team Manager:  Michel VIDAL, DR CNRS




Assistant Professor UM2

pbobillo arobase univ-montp2.fr


Technical assistant UM2

anne.bonhoure arobase univ-montp2.fr

VIDAL Michel


michel.vidal arobase univ-montp2.fr


While most extracellularly secreted proteins go through classical ER-Golgi pathway due to the presence of signal peptide, some cytosolic proteins employ various mechanisms for their unconventional secretion. Exosome secretion is one of these mechanisms. Exosomes are cell-secreted nanovesicles (60-100 nm) formed by inward budding of the endosomal membrane and thus trapping cytosol inside. The so-formed multivesicular bodies then fuse with the plasma membrane releasing intraluminal vesicles, at this point called exosomes, in the extracellular medium. Other mechanisms of unconventional secretion involve either direct transport of cytosolic proteins across membranes or fusion of autophagosome with the plasma membrane.


Research objectives

Aim 1:  Unconventional secretion of proteins
One of our objectives is to elucidate the mechanisms involved in TCTP homeostasis in cells. TCTP (translationally controlled tumor protein) is a cytosolic multifunctional protein, which has been demonstrated to be a key factor in tumor reversion and whose intracellular level is correlated with clinical and pathological parameters of cancer aggressiveness. We have demonstrated that TCTP can be secreted associated with exosomes and also lysosome-degraded through chaperone-mediated autophagy. However, TCTP is also secreted as a free protein (HRF: histamine-releasing factor) inducing histamine release from basophils and mast cells. TCTP is secreted by an alternative pathway since it does not contain a signal peptide required for a classical secretion. The mechanism of TCTP unconventional secretion and its connection with other removal pathways will be investigated. Moreover, we have also evidenced the presence of proteasome (20S) in our purified exosomal fractions and we are currently studying the mechanism of this proteasome release.

Aim 2: Exosome biogenesis and function
The team’s projects aim to decipher the molecular bases of exosome biogenesis, for a better understanding of their potential (patho)-physiological functions. We have demonstrated that the exosomal pathway is crucial during the last stage of erythropoiesis, regulating (through membrane disposal) the expression of specific membrane proteins on the surface of mature red blood cells and likely allowing the reticulocyte to adapt to environmental changes (bone marrow vs blood circulation) during its maturation.
We are also interested by the functions of exosomes in pathology (e.g. melanoma-derived exosomes) and will study various processes in conjunction with specific exosomal protein activities.

Publications on the topic

A. Bonhoure, A. Vallentin, M. Martin, A. Senff-Ribeiro, R. Amson, A. Telerman   and M. Vidal (2017) Acetylation of Translationally Controlled Tumor Protein promotes its degradation through Chaperone-Mediated Autophagy. Eur. J. Cell Biol 96:83-98.

L. Blanc and M. Vidal (2017) New Insights into the function of Rab GTPases in the context of exosomal secretion. Small GTPases (in press) DOI: 10.1080/21541248.2016.1264352.

D.J. Klionsky et al. (2015) Guidelines for the Use and Interpretation of Assays for Monitoring Autophagy (2nd edition) Autophagy 12(1):1-222.

L. Blanc, J. Papoin, G. Debnath, M. Vidal, R. Amson, A. Telerman, X. An, and N. Mohandas. (2015) Defective erythropoiesis leads to microcytic anemia in the TSAP6/Steap3 null mouse model. Am. J. Hematol. 90(3): 235-41.

H. Kalra, …, M. Vidal,… and S. Mathivanan (2012) Vesiclepedia : a compendium for extracellular vesicles with continuous community annotation. PLoS Biology 10(12), e1001450.

K. Kiss, A. Brozik, N. Kucsma, A. Toth, M. Gera, L. Berry, A. Vallentin, H. Vial, M. Vidal and G. Szakacs (2012) Shifting the paradigm: the putative mitochondrial protein ABCB6 resides in the lysosomes of cells and in the plasma membrane of erythrocytes. PLoS ONE 7(5): e37378.

GA. Rabinovich and M. Vidal (2011) Galectins and microenvironmental niches during hematopoiesis. Curr. Opin. Hematol. 18, 443-451.

L. Blanc and M. Vidal (2010) Reticulocyte membrane remodeling : contribution of the exosome pathway. Curr. Opin. Hematol. 17, 177-183.

C. Barrès, L. Blanc, P. Bette-Bobillo, S. André, R. Mamoun, HJ. Gabius and M. Vidal (2010) Galectin-5 is bound onto the surface of rat reticulocyte exosomes and modulates vesicle uptake by macrophages. Blood 115(3), 696-705.

L. Blanc, J. Liu, M. Vidal, JA. Chasis, X. An and N. Mohandas (2009) The water channel aquaporin-1 partitions into exosomes during reticulocyte maturation: implication for the regulation of cell volume. Blood 114(18), 3928-34.

A. De Gassart, B. Trentin, M. Martin, A. Hocquellet, P. Bette-Bobillo, R. Mamoun and M. Vidal (2009) Exosomal sorting of the cytoplasmic domain of bovine leukemia virus TM Env protein. Cell Biol Int. 33, 36-48.

A. Lespagnol, D. Duflaut, C. Beekman, L. Blanc, G. Fiucci, J.C. Marine , M. Vidal, R. Amson, A. Telerman. (2008) Exosome secretion, including the DNA damage-induced p53-dependent secretory pathway, is severely compromised in TSAP6/Steap3-null mice. Cell Death Differ. 15 (11), 1723-1733.

L. Blanc, C. Barres, P. Bette-Bobillo and M. Vidal (2007) Reticulocyte-secreted exosomes bind natural IgM antibodies: Involvement of a ROS-activatable endosomal phospholipase iPLA2. Blood 110, 3407-3416.

A. de Gassart, C. Géminard, D. Hoekstra and M. Vidal (2004) Exosome secretion: the art of reutilizing nonrecycled proteins? Traffic 5, 896-903

B. Février, D. Vilette, F. Archer, D. Loew, W. Faigle, M. Vidal, H. Laude and G. Raposo (2004) Cells release prions in association with exosomes. Proc. Natl. Acad. Sci. USA 101, 9683-9688.

C. Géminard, A. de Gassart, L. Blanc and M. Vidal (2004) Degradation of AP2 during reticulocyte maturation enhances binding of hsc70 and Alix to a common site on TfR for sorting into exosomes. Traffic 5, 181-93.

A. de Gassart, C. Géminard, B. Février, G. Raposo and M. Vidal (2003) Lipid raft-associated proteins are sorted in exosomes. Blood 102, 4336-4344M.

A. Savina, M. Furlán, M. Vidal and M.I. Colombo (2003) Monensin stimulates exosome release by a calcium-dependent mechanism. J. Biol. Chem. 278, 20083-90.

A. Savina, M. Vidal and M.I. Colombo (2002) The exosome pathway in K562 cells is regulated by Rab11. J. Cell Sci. 115, 2505-2515.

C. Géminard, Nault, F., Johnstone, R. M., and M.Vidal (2001) Characteristics of the interaction between Hsc70 and the transferrin receptor in exosomes released during reticulocyte maturation. J. Biol. Chem. 276, 9910-6.

S. Rieu, C. Géminard, H. Rabesandratana, J. Sainte-Marie and M. Vidal (2000) Exosomes released during reticulocyte maturation bind to fibronectin via integrin 41. Eur. J. Biochem. 267, 583-590.

H. Rabesandratana, J.P. Toutant, H. Reggio and M. Vidal (1998) Decay-accelerating factor (CD55) and membrane inhibitor of reactive lysis (CD59) are released within exosomes during in vitro maturation of reticulocyte. Blood 91, 2573-2580

M. Vidal, P. Mangeat and D. Hoekstra (1997) Aggregation reroutes molecules from a recycling to a shedding pathway during reticulocyte maturation. J. Cell Sci. 110, 1867-1877

M. Vidal and P.D. Stahl (1993) The small GTP-binding proteins Rab4 and ARF are associated with released exosomes during reticulocyte maturation. Eur. J. Cell Biol. 60, 261-267.

M. Vidal, J. Sainte-Marie, J.R. Philippot and A. Bienvenüe (1989) Asymmetric distribution of phospholipids in the membrane of vesicles released during in vitro maturation of guinea pig reticulocytes: evidence precluding a role for "aminophospholipid translocase". J. Cell. Physiol. 140, 455-462.



P.E. Stoebner, UMR 5247, Montpellier
A. Telerman & R. Amson, Inst. Gustave Roussy, Villejuif
L. Blanc, Feinstein Institute for Medical Research, Manhasset, NY
N. Mohandas, New York Blood Center, NY