A Conserved Structural Motif Mediates Retrograde Trafficking of Shiga Toxin Types 1 and 2

作者：Selyunin Andrey S; Mukhopadhyay Somshuvra^*

来源：Traffic, 2015, 16(12): 1270-1287.

DOI：10.1111/tra.12338

• bacterial toxin
• endosome
• Golgi
• protein motif
• trafficking

Shiga toxin-producing Escherichia coli (STEC) produce two types of Shiga toxin (STx): STx1 and STx2. The toxin A-subunits block protein synthesis, while the B-subunits mediate retrograde trafficking. STEC infections do not have definitive treatments, and there is growing interest in generating toxin transport inhibitors for therapy. However, a comprehensive understanding of the mechanisms of toxin trafficking is essential for drug development. While STx2 is more toxic in vivo, prior studies focused on STx1 B-subunit (STx1B) trafficking. Here, we show that, compared with STx1B, trafficking of the B-subunit of STx2 (STx2B) to the Golgi occurs with slower kinetics. Despite this difference, similar to STx1B, endosome-to-Golgi transport of STx2B does not involve transit through degradative late endosomes and is dependent on dynamin II, epsinR, retromer and syntaxin5. Importantly, additional experiments show that a surface-exposed loop in STx2B (beta 4-beta 5 loop) is required for its endosome-to-Golgi trafficking. We previously demonstrated that residues in the corresponding beta 4-beta 5 loop of STx1B are required for interaction with GPP130, the STx1B-specific endosomal receptor, and for endosome-to-Golgi transport. Overall, STx1B and STx2B share a common pathway and use a similar structural motif to traffic to the Golgi, suggesting that the underlying mechanisms of endosomal sorting may be evolutionarily conserved.

• 出版日期2015-12