Human Gb3/CD77 synthase: a glycosyltransferase at the crossroads of immunohematology, toxicology, and cancer research.

Human Gb3/CD77 synthase (α1,4-galactosyltransferase, P1/P^k synthase, UDP-galactose: β-D-galactosyl-β1-R 4-α-D-galactosyltransferase, EC 2.4.1.228) forms Galα1 → 4Gal structures on glycosphingolipids and glycoproteins. These glycans are recognized by bacterial adhesins and toxins. Globotriaosylceramide (Gb3), the major product of Gb3/CD77 synthase, is a glycosphingolipid located predominantly in plasma membrane lipid rafts, where it serves as a main receptor for Shiga toxins released by enterohemorrhagic Escherichia coli and Shigella dysenteriae of serotype 1. On the other hand, accumulation of glycans formed by Gb3/CD77 synthase contributes to the symptoms of Anderson-Fabry disease caused by α-galactosidase A deficiency. Moreover, variation in Gb3/CD77 synthase expression and activity underlies the P1PK histo-blood group system. Glycosphingolipids synthesized by the enzyme are overproduced in colorectal, gastric, pancreatic, and ovarian cancer, and elevated Gb3 biosynthesis is associated with cancer cell chemo- and radioresistance. Furthermore, Gb3/CD77 synthase acts as a key glycosyltransferase modulating ovarian cancer cell plasticity. Here, we describe the role of human Gb3/CD77 synthase and its products in the P1PK histo-blood group system, Anderson-Fabry disease, and bacterial infections. Additionally, we provide an overview of emerging evidence that Gb3/CD77 synthase and its glycosphingolipid products are involved in cancer metastasis and chemoresistance.