Arylsulfatase G inactivation causes loss of heparan sulfate 3-O-sulfatase activity and mucopolysaccharidosis in mice.

Deficiency of glycosaminoglycan (GAG) degradation causes a subclass of lysosomal storage disorders called mucopolysaccharidoses (MPSs), many of which present with severe neuropathology. Critical steps in the degradation of the GAG heparan sulfate remain enigmatic. Here we show that the lysosomal arylsulfatase G (ARSG) is the long-sought glucosamine-3-O-sulfatase required to complete the degradation of heparan sulfate. Arsg-deficient mice accumulate heparan sulfate in visceral organs and the central nervous system and develop neuronal cell death and behavioral deficits. This accumulated heparan sulfate exhibits unique nonreducing end structures with terminal N-sulfoglucosamine-3-O-sulfate residues, allowing diagnosis of the disorder. Recombinant human ARSG is able to cleave 3-O-sulfate groups from these residues as well as from an authentic 3-O-sulfated N-sulfoglucosamine standard. Our results demonstrate the key role of ARSG in heparan sulfate degradation and strongly suggest that ARSG deficiency represents a unique, as yet unknown form of MPS, which we term MPS IIIE.

The heparanome--the enigma of encoding and decoding heparan sulfate sulfation.

Heparan sulfate (HS) is a cell surface carbohydrate polymer modified with sulfate moieties whose highly ordered composition is central to directing specific cell signaling events. The ability of the cell to generate these information rich glycans with such specificity has opened up a new field of "heparanomics" which seeks to understand the systems involved in generating these cell type and developmental stage specific HS sulfation patterns. Unlike other instances where biological information is encrypted as linear sequences in molecules such as DNA, HS sulfation patterns are generated through a non-template driven process. Thus, deciphering the sulfation code and the dynamic nature of its generation has posed a new challenge to system biologists. The recent discovery of two sulfatases, Sulf1 and Sulf2, with the unique ability to edit sulfation patterns at the cell surface, has opened up a new dimension as to how we understand the regulation of HS sulfation patterning and pattern-dependent cell signaling events. This review will focus on the functional relationship between HS sulfation patterning and biological processes. Special attention will be given to Sulf1 and Sulf2 and how these key editing enzymes might act in concert with the HS biosynthetic enzymes to generate and regulate specific HS sulfation patterns in vivo. We will further explore the use of knock out mice as biological models for understanding the dynamic systems involved in generating HS sulfation patterns and their biological relevance. A brief overview of new technologies and innovations summarizes advances in the systems biology field for understanding non-template molecular networks and their influence on the "heparanome".

Heparan sulfate 6-O-endosulfatases: discrete in vivo activities and functional co-operativity.

HS (heparan sulfate) is essential for normal embryonic development. This requirement is due to the obligatory role for HS in the signalling pathways of many growth factors and morphogens that bind to sulfated domains in the HS polymer chain. The sulfation patterning of HS is determined by a complex interplay of Golgi-located N- and O-sulfotransferases which sulfate the heparan precursor and cell surface endosulfatases that selectively remove 6-O-sulfates from mature HS chains. In the present study we generated single or double knock-out mice for the two murine endosulfatases mSulf1 and mSulf2. Detailed structural analysis of HS from mSulf1-/- fibroblasts showed a striking increase in 6-O-sulfation, which was not seen in mSulf2-/- HS. Intriguingly, the level of 6-O-sulfation in the double mSulf1-/-/2-/- HS was significantly higher than that observed in the mSulf1-/- counterpart. These data imply that mSulf1 and mSulf2 are functionally co-operative. Unlike their avian orthologues, mammalian Sulf activities are not restricted to the highly sulfated S-domains of HS. Mitogenesis assays with FGF2 (fibroblast growth factor 2) revealed that Sulf activity decreases the activating potential of newly-synthesized HS, suggesting an important role for these enzymes in cell growth regulation in embryonic and adult tissues.