The SULFs, Extracellular Sulfatases for Heparan Sulfate, Promote the Migration of Corneal Epithelial Cells during Wound Repair

Abstract

Corneal epithelial wound repair involves the migration of epithelial cells to cover the defect followed by the proliferation of the cells to restore thickness. Heparan sulfate proteoglycans (HSPGs) are ubiquitous extracellular molecules that bind to a plethora of growth factors, cytokines, and morphogens and thereby regulate their signaling functions. Ligand binding by HS chains depends on the pattern of four sulfation modifications, one of which is 6-O-sulfation of glucosamine (6OS). SULF1 and SULF2 are highly homologous, extracellular endosulfatases, which post-synthetically edit the sulfation status of HS by removing 6OS from intact chains. The SULFs thereby modulate multiple signaling pathways including the augmentation of Wnt/ß-catenin signaling. We found that wounding of mouse corneal epithelium stimulated SULF1 expression in superficial epithelial cells proximal to the wound edge. Sulf1−/−, but not Sulf2−/−, mice, exhibited a marked delay in healing. Furthermore, corneal epithelial cells derived from Sulf1−/− mice exhibited a reduced rate of migration in repair of a scratched monolayer compared to wild-type cells. In contrast, human primary corneal epithelial cells expressed SULF2, as did a human corneal epithelial cell line (THCE). Knockdown of SULF2 in THCE cells also slowed migration, which was restored by overexpression of either mouse SULF2 or human SULF1. The interchangeability of the two SULFs establishes their capacity for functional redundancy. Knockdown of SULF2 decreased Wnt/ß-catenin signaling in THCE cells. Extracellular antagonists of Wnt signaling reduced migration of THCE cells. However in SULF2- knockdown cells, these antagonists exerted no further effects on migration, consistent with the SULF functioning as an upstream regulator of Wnt signaling. Further understanding of the mechanistic action of the SULFs in promoting corneal repair may lead to new therapeutic approaches for the treatment of corneal injuries.

SULF2, a heparan sulfate endosulfatase, is present in the blood of healthy individuals and increases in cirrhosis

“…The SULF1 goat anti-peptide antibody (G1.6) was previously described [10]. The specificity of the novel mAbs was evaluated by ELISA aqs follows.…”

Comparative and Evolutionary Studies of Vertebrate Extracellular Sulfatase Genes and Proteins: SULF1 and SULF2

“…Structures for vertebrate SULF1 and SULF2 genes and cDNA sequences have been reported, including human (Homo sapiens) [3]; mouse (Mus musculus) [5,22,23]; rat (Rattus norvegicus) [24,25]; frog (Xenopus laevis) [13][14]; and zebra fish (Danio rerio) [16] SULF genes. Human SULF1, which spans 194.3 kilobases and comprises 22 exons, is localized on chromosome 8; whereas human SULF2 spans 128.7 kilobases and comprises 21 exons on chromosome 20 [26,27].…”

“…Human SULF1, which spans 194.3 kilobases and comprises 22 exons, is localized on chromosome 8; whereas human SULF2 spans 128.7 kilobases and comprises 21 exons on chromosome 20 [26,27]. Both of these genes are widely expressed in the body, consistent with their overlapping and essential roles in cell signaling pathways, skeletal muscle regeneration, neonatal development and survival, metastasis and wound repair [9,18,19,23]. This paper reports the predicted gene structures and amino acid sequences for several vertebrate SULF1 and SULF2 genes and proteins, the predicted secondary and tertiary structures for human SULF1 and SULF2 protein subunits, and the structural, phylogenetic and evolutionary relationships for these genes and enzymes.…”

Sulfatase 2 facilitates lymphangiogenesis in breast cancer by regulating VEGF-D

“…Extracellular sulfatases, especially heparan endosulfatases (Sulfs), play important roles in cancer progression by modifying the sulfate patterns of heparan sulfate proteoglycans (HSPGs) located on the surface of most animal cells (1–3). HSPGs can be released into the extracellular matrix and can also be detected in serum.…”