QSulf1 remodels the 6-O sulfation states of cell surface heparan sulfate proteoglycans to promote Wnt signaling

Abstract

The 6-O sulfation states of cell surface heparan sulfate proteoglycans (HSPGs) are dynamically regulated to control the growth and specification of embryonic progenitor lineages. However, mechanisms for regulation of HSPG sulfation have been unknown. Here, we report on the biochemical and Wnt signaling activities of QSulf1, a novel cell surface sulfatase. Biochemical studies establish that QSulf1 is a heparan sulfate (HS) 6-O endosulfatase with preference, in particular, toward trisulfated IdoA2S-GlcNS6S disaccharide units within HS chains. In cells, QSulf1 can function cell autonomously to remodel the sulfation of cell surface HS and promote Wnt signaling when localized either on the cell surface or in the Golgi apparatus. QSulf1 6-O desulfation reduces XWnt binding to heparin and HS chains of Glypican1, whereas heparin binds with high affinity to XWnt8 and inhibits Wnt signaling. CHO cells mutant for HS biosynthesis are defective in Wnt-dependent Frizzled receptor activation, establishing that HS is required for Frizzled receptor function. Together, these findings suggest a two-state “catch or present” model for QSulf1 regulation of Wnt signaling in which QSulf1 removes 6-O sulfates from HS chains to promote the formation of low affinity HS–Wnt complexes that can functionally interact with Frizzled receptors to initiate Wnt signal transduction.

Insulin modulates the secretion of proteins from mature 3T3-L1 adipocytes: a role for transcriptional regulation of processing

“…Our results suggest that besides glucose, insulin might independently induce a pattern change in HSPG in cultured adipocytes. Immunocytochemical analysis with the antibody 10E4 (Seikagaku, Tokyo, Japan) has been used to assay the 6-O de-sulfation by transfected Qsulf1 in 3T3-L1 fibroblasts [40]. Using this antibody, we failed to detect a significant decrease of HSPG sulfation in 3T3-L1 mature adipocytes after treatment with insulin (data not shown).…”

Heparan sulfate Ndst1 gene function variably regulates multiple signaling pathways during mouse development

“…A second Copp et al, 2003). HS is known to bind to Wnt/Wg (Ai et al, 2003), and notably, reduced Wnt signaling was observed in the presumptive midbrain, hindbrain, and spinal cord of 30% of the Ndst1 Ϫ/Ϫ embryos. This finding indicates that NTDs in Ndst1-deficient embryos may (partially) be based on impaired Wnt signaling.…”

Dynamic expression patterns of 6‐O endosulfatases during zebrafish development suggest a subfunctionalisation event for sulf2

“…Sulfs are regarded as the final edihighly sulfated domains of HS (Ai et al, 2003). However, Sulfs are capable of modifying the transition and low-sulfated domains (Lamanna et al, 2006;Ai et al, 2007).…”

“…Dynamic changes in HS sulfation by the Sulfs have been shown to modulate a number of signalling molecules including Shh, Wnt, Bone Morphogenic Protein-4 (BMP4), Glial Derived Neurotrophic Factor (GDNF), Fibroblast Growth Factor (FGF), and Vascular Endothelial Growth Factor (VEGF). Sulfs control Wnt-dependent myogenesis by allowing Wnt to freely associate with its receptor (Dhoot et al, 2001), regulate oligodendroglial specification by enhancing the diffusion gradient of Shh (Danesin et al, 2006), mediate mesoderm induction and angiogenesis through an FGF/HS/ FGF receptor (FGFR) complex (Ai et al, 2003), regulate GDNF-mediated muscle innervation and regeneration (Ai et al, 2007), and also regulate BMP4 signalling by inhibiting the interaction with its cognate receptor (Freeman et al, 2008). Thus, Sulf enzymes can regulate HS-dependent signalling in both a positive and negative manner, depending on the interaction of 6-O sulfation with the HS-binding protein.…”