VAMP7, A POSSIBLE SNARE INVOLVED IN EXOSOMES RELEASE IN K562 CELLS

SANCHEZ D, FADER CM, AND COLOMBO MI

Rosario, Santa Fe, Argentina

Congreso; XLII Annual Meeting SAIB 2006; 2006

Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB)

Multivesicular bodies (MVBs) are membranous structures, which accumulate small vesicles in the lumen of the vacuole. These structures are an intermediate state between the early endosome/lysosome compartments. Fusion of MVBs with the plasma membrane results in the release of the internal vesicles called exosomes. The aim of this work is the identification of the SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) involved in the fusion of MVBs with the plasma membrane. We show that TI-VAMP (tetanus neurotoxin-insensitive vesicle-associated membrane protein)/VAMP7 colocalize with the MVBs marker N-Rh-PE (N-lisamina rhodamine B sulfonyl-phosphatidylethanolamine). VAMP7 also colocalized with Rab11, a small monomeric GTPasa that participates in homotypic fusion of MVBs. Overexpression of the dominant negative amino-terminal domain of VAMP7 (NT-VAMP7) markedly reduced exosomes release. Furthermore we used N-ethylmaleimide (NEM), an inhibitior of NSF (N-ethylmaleimide-sensitive factor), and we observed an accumulation of Rab11 positive vesicles labeled with N-Rh-PE at the plasma membrane. Our data suggest that Rab11 likely participates in the transport of MVBs to the plasma membrane and VAMP7 is involved in this docking/fusion event.