Desulfation of Heparan Sulfate by Sulf1 and Sulf2 Is Required for Corticospinal Tract Formation.

Heparan sulfate (HS) has been implicated in a wide range of cell signaling. Here we report a novel mechanism in which extracellular removal of 6-O-sulfate groups from HS by the endosulfatases, Sulf1 and Sulf2, is essential for axon guidance during development. In Sulf1/2 double knockout (DKO) mice, the corticospinal tract (CST) was dorsally displaced on the midbrain surface. In utero electroporation of Sulf1/2 into radial glial cells along the third ventricle, where Sulf1/2 mRNAs are normally expressed, rescued the CST defects in the DKO mice. Proteomic analysis and functional testing identified Slit2 as the key molecule associated with the DKO phenotype. In the DKO brain, 6-O-sulfated HS was increased, leading to abnormal accumulation of Slit2 protein on the pial surface of the cerebral peduncle and hypothalamus, which caused dorsal repulsion of CST axons. Our findings indicate that postbiosynthetic desulfation of HS by Sulfs controls CST axon guidance through fine-tuning of Slit2 presentation.

Association of ubiquitin carboxy-terminal hydrolase-L1 in cerebrospinal fluid with clinical severity in a cohort of patients with Guillain-Barré syndrome.

Guillain-Barré syndrome (GBS) is an acute immune-mediated polyneuropathy. Although its pathogenic mechanism has been revealed and various therapeutic trials have been performed, a proportion of patients experience the severe sequelae associated with GBS. In this paper, we investigated whether the amount of the neuron-specific protein, ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1), in the cerebrospinal fluid of patients with GBS was correlated with the clinical course of the disease. UCH-L1 protein levels were greater in patients with GBS than in controls. The patients with GBS whose UCH-L1 protein levels were higher than those of the controls presented with more severe symptoms at peak. UCH-L1 protein levels tended to become elevated as the total protein levels were increased; however, elevated UCH-L1 without an increase in total protein might be correlated with severe disease course (bedridden or ventilator supported). These results suggest that UCH-L1 could be a biomarker associated with the severity of the disease at the acute phase of GBS.

Organ-specific sulfation patterns of heparan sulfate generated by extracellular sulfatases Sulf1 and Sulf2 in mice.

Heparan sulfate endosulfatases Sulf1 and Sulf2 hydrolyze 6-O-sulfate in heparan sulfate, thereby regulating cellular signaling. Previous studies have revealed that Sulfs act predominantly on UA2S-GlcNS6S disaccharides and weakly on UA-GlcNS6S disaccharides. However, the specificity of Sulfs and their role in sulfation patterning of heparan sulfate in vivo remained unknown. Here, we performed disaccharide analysis of heparan sulfate in Sulf1 and Sulf2 knock-out mice. Significant increases in ΔUA2S-GlcNS6S were observed in the brain, small intestine, lung, spleen, testis, and skeletal muscle of adult Sulf1(-/-) mice and in the brain, liver, kidney, spleen, and testis of adult Sulf2(-/-) mice. In addition, increases in ΔUA-GlcNS6S were seen in the Sulf1(-/-) lung and small intestine. In contrast, the disaccharide compositions of chondroitin sulfate were not primarily altered, indicating specificity of Sulfs for heparan sulfate. For Sulf1, but not for Sulf2, mRNA expression levels in eight organs of wild-type mice were highly correlated with increases in ΔUA2S-GlcNS6S in the corresponding organs of knock-out mice. Moreover, overall changes in heparan sulfate compositions were greater in Sulf1(-/-) mice than in Sulf2(-/-) mice despite lower levels of Sulf1 mRNA expression, suggesting predominant roles of Sulf1 in heparan sulfate desulfation and distinct regulation of Sulf activities in vivo. Sulf1 and Sulf2 mRNAs were differentially expressed in restricted types of cells in organs, and consequently, the sulfation patterns of heparan sulfate were locally and distinctly altered in Sulf1 and Sulf2 knock-out mice. These findings indicate that Sulf1 and Sulf2 differentially contribute to the generation of organ-specific sulfation patterns of heparan sulfate.

Deficiency of ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1) leads to vulnerability to lipid peroxidation.

Lipid peroxidation has many deleterious effects on cells, and in the nervous system is considered to be involved in the pathogenesis of neurodegenerative diseases. To suppress lipid peroxidation, cells have various defense systems such as glutathione and thioredoxin, and defects in these defense systems will result in disturbance of normal cellular functions. Here we report that deficiency of ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1) leads to vulnerability to lipid peroxidation both in vivo and in vitro, through analyses of the UCH-L1-deficient mutant mouse gracile axonal dystrophy (gad). In the gracile fasciculus of gad mice, punctate deposits were observed to be immunoreactive for 4-hydroxy-2-nonenal, a by-product of lipid peroxidation. The motor deficits of gad mice were worsened by a diet deficient in vitamin E. When neurons from dorsal root ganglions (DRG) were cultured in the vitamin E-free medium, cell death was increased in the neurons of gad mice. These data suggest that UCH-L1 has a function in protecting DRG neurons from lipid peroxidation. Further, we describe newly identified properties: that UCH-L1 is localized on the inside of the plasma membrane of DRG neurons, and that UCH-L1 binds to phosphatidic acid according to the redox status and presence of mono-ubiquitin protein. These findings will provide clues for elucidating the physiological function of UCH-L1.

Proteolytic cleavage of the rat heparan sulfate 6-O-endosulfatase SulfFP2 by furin-type proprotein convertases.

Heparan sulfate 6-O-endosufatases Sulf1 and Sulf2 hydrolyze the 6-O-sulfate of the glucosamine residues in heparin and heparan sulfate, thereby regulating multiple signaling pathways. A previous study reported that human Sulf1 and Sulf2 were proteolytically processed in a manner sensitive to a furin inhibitor. However, the exact sites of cleavage, the sequence motifs for proteolysis, and the effect of the cleavage on enzyme activity remain unknown. Here we show that the cleavage of rat Sulf2 (also called SulfFP2) occurs at two arginine residues, 543 and 570, in the hydrophilic domain. Both sites reside in the consensus sequence for the cleavage by furin-type proprotein convertases, and the consensus motifs are essential for cleavages. The cleavage at arginine 570 is sensitive to a furin inhibitor. Furthermore, the uncleavable form of SulfFP2 shows sulfatase activity comparable to the cleavable SulfFP2, indicating that the cleavage is not indispensable for activation of SulfFP2.

Reduction in memory in passive avoidance learning, exploratory behaviour and synaptic plasticity in mice with a spontaneous deletion in the ubiquitin C-terminal hydrolase L1 gene.

Overexpression of ubiquitin C-terminal hydrolase L1 (UCH-L1) in mice rescues amyloid beta-protein-induced decreases in synaptic plasticity and memory. However, the physiological role of UCH-L1 in the brain is not fully understood. In the present study, we investigated the role of UCH-L1 in the brain by utilizing gracile axonal dystrophy (gad) mice with a spontaneous deletion in the gene Uch-l1 as a loss-of-function model. Although gad mice exhibit motor paresis beginning at approximately 12 weeks of age, it is possible to analyse their brain phenotypes at a younger age when no motor paresis is evident. Maintenance of memory in a passive avoidance test and exploratory behaviour in an open field test were reduced in 6-week-old gad mice. The maintenance of theta-burst stimulation-induced long-term potentiation (LTP) of field synaptic responses from Schaffer collaterals to CA1 pyramidal cells in hippocampal slices was also impaired in gad mice. The LTP in gad mice was insensitive to actinomycin D, suggesting that a transcription-dependent component of the LTP is impaired. Phosphorylation of cyclic AMP response element binding protein (CREB) in the CA1 region of hippocampal slices from gad mice occurred earlier than in the slices from wild-type mice and was transient, suggesting that CREB phosphorylation is altered in gad mice. These results suggest that memory in passive avoidance learning, exploratory behaviour and hippocampal CA1 LTP are reduced in gad mice. We propose that UCH-L1-mediated maintenance of the temporal integrity and persistence of CREB phosphorylation underlies these impairments.

Expression of a heparan sulfate remodeling enzyme, heparan sulfate 6-O-endosulfatase sulfatase FP2, in the rat nervous system.

A new class of sulfatases, SulfFP1/sulf-1 and SulfFP2/sulf-2, has been implicated in the modulation of extracellular signaling by remodeling heparan sulfate through 6-O-endosulfatase activity. Here, we isolated rat SulfFP2 cDNA and examined its expression by in situ hybridization. SulfFP2 expression is abundant and dynamically regulated in the nervous system during development, whereas it is confined to the cerebral cortex, hippocampal CA3 region, and medial habenular nucleus in the adult brain.