HNK-1 Sulfotransferase

Abstract

The HNK-1 epitope was originally described as a marker of a subfraction of human natural killer cells (Abo and Balch 1981). Despite its name, the HNK-1 carbohydrate epitope is found in many tissues but is predominantly expressed in the mammalian nervous system. The expression pattern of the HNK-1 carbohydrate in both the central and peripheral nervous system is spatially and developmentally regulated. In the nervous system the HNK-1 carbohydrate epitope is carried by many neural recognition glycoproteins and is involved in homophilic and heterophilic binding of these proteins (Schachner and Martini 1995). The epitope is characterized by the structure SO₄-3GlcAβ1-3Galβ(1-4GlcNAc) at the nonreducing end of glycans found on glycoproteins (N- and O-linked) (Voshol et al. 1996; Wakabayashi et al. 1999) and glycolipids (Chou et al. 1986). The key enzymes in the biosynthesis of HNK-1 carbohydrates are a glucuronyltransferase (GlcA-transferase) (Terayama et al. 1997) (see Chapter 51) and a sulfotransferase, as the underlying lactosamine structure is commonly found in glycoconjugates. The sulfotransferase enzyme catalyzing the transfer of sulfate from the donor substrate 3′-phosphoadenosine 5′-phosphosulfate (PAPS) to the glucuronic acid containing glycolipid or glycoprotein acceptor was first characterized by Chou and Jungalwala (1993), and the cDNA was first cloned by Bakker et al. (1997).