Shiga toxin subunit B (StxB) (StxB)

Shiga toxin subunit B (StxB) is the non-toxic, pentameric component of the Shiga toxin produced by Shigella dysenteriae and Shiga toxin-producing Escherichia coli (STEC) (UniProt: P09385). Its primary biological function is to mediate high-affinity binding to the glycosphingolipid globotriaosylceramide (Gb3 or CD77) on the plasma membrane of host cells, particularly in the intestinal mucosa and renal endothelium (Johannes & Römer, 2010). Following binding, StxB facilitates the internalization of the holotoxin via a specialized retrograde transport pathway that bypasses the degradative lysosomal route, moving instead through the Golgi apparatus to the endoplasmic reticulum (Malyukova et al., 2009). This process is essential for the pathogenesis of shigellosis and hemolytic uremic syndrome (HUS), as it allows the catalytic A subunit to reach the cytosol and inhibit protein synthesis. In clinical development, StxB is a major target for neutralizing monoclonal antibodies, such as Urtoxazumab, which aim to prevent toxin-mediated organ damage (Bitzan et al., 2009). Additionally, the specific binding of StxB to Gb3-overexpressing cells has led to its investigation as a targeted delivery vehicle for chemotherapeutic agents and imaging probes in various cancers (Engedal et al., 2011).

Other names

StxBVerotoxin subunit BVT-BShiga-like toxin subunit BSLT-BStx1BStx2B

Neutralization of the B-subunit prevents the toxin from binding to the host cell receptor globotriaosylceramide (Gb3), thereby blocking cellular entry and subsequent inhibition of protein synthesis (Johannes & Römer, 2010).