Shiga toxin stimulates clathrin-independent endocytosis of VAMP2/3/8 SNARE proteins

Endocytosis is an essential cellular process that is often hijacked by pathogens and pathogenic products. Endocytic processes can be classified into two broad categories, dependent or not on clathrin. The SNARE proteins VAMP2, 3 and 8 are internalized in a clathrin-dependent manner. Yet, the full scope of their endocytic behavior has not yet been elucidated. Here, we found that VAMP2, 3, and 8 are localized on plasma membrane invaginations and very early uptake structures that are induced by the bacterial Shiga toxin, which enters cells by clathrin-independent endocytosis. We show that toxin trafficking into cells and cell intoxication rely on these SNARE proteins. Of note, the cellular uptake of VAMP2, 3, and 8 is increased in the presence of Shiga toxin, even when their clathrin-dependent endocytosis is blocked. We therefore conclude that VAMP2, 3, and 8 are removed from the plasma membrane via non-clathrin pathways, in addition to their clathrin-dependent uptake. Moreover, our study identifies these SNARE proteins as the first transmembrane trafficking factors that functionally associate at the plasma membrane with the toxin-driven clathrin-independent uptake process.