Apoptosis induced in Burkitt's lymphoma cells via Gb3/CD77, a glycolipid antigen

Gb3/CD77 is a glycolipid antigen, specifically expressed on two different B-cell populations, Burkitt's lymphoma and a subset of tonsillar B-lymphocytes located in germinal centers, which could be the normal counterpart of Burkitt cells. Both Gb3/CD77(+) populations have recently been shown to enter programmed cell death (apoptosis) readily. Here we show that verotoxin, also called Shiga-like toxin, which is known to bind to the carbohydrate moiety of Gb3/CD77, induces cell death in Gb3/CD77(+) Burkitt's lymphoma cells, not only by inhibiting protein synthesis as classically described but also through an additional mechanism, namely apoptosis. Furthermore a recombinant B-subunit of verotoxin, which carries only the binding property of the holotoxin, also induces apoptosis in Gb3/CD77(+) cells. Gb3/CD77 could thus represent the first example of a glycolipid antigen able to transduce a signal leading to apoptosis.