Microglial Keratan Sulfate Epitope Elicits in Central Nervous Tissues of Transgenic Model Mice and Patients with Amyotrophic Lateral Sclerosis

Abstract

The functional role of 5D4 antibody-reactive keratan sulfate (KS) in the pathogenesis of neurodegenerative diseases is unknown. We therefore studied the expression of 5D4-reactive KS in amyotrophic lateral sclerosis (ALS), a motor neuron-degenerative disease, with the use of SOD1(G93A) ALS model mice and patients with ALS. Histochemical and immunoelectron microscopic characterizations showed that the 5D4-reactive KS is expressed in Mac2/galectin-3-positive activated or proliferating microglia of SOD1(G93A) ALS model mice at disease end stage and that the KS is an O-linked glycan modified with sialic acid and fucose, which was thus far shown to exist in cartilage. Intriguingly, microglial KS was detected in the spinal cord and brainstem but not in the cerebral cortex of SOD1(G93A) mice. We found that KSGal6ST, a galactose-6-sulfotransferase, is required for biosynthesis of the microglial 5D4-reactive KS by generating SOD1(G93A)/KSGal6ST(-/-) mice. The requirement of GlcNAc6ST1 for this synthesis was corroborated by analyzing SOD1(G93A)/GlcNAc6ST1(-/-) mice. These results indicate that both galactose-6- and N acteylglucosamine-6-sulfated KS elicited in the spinal cord and brainstem are associated with the degeneration of spinal and bulbar lower motor neurons in ALS pathology and may play a role in disease progression via microglial activation and proliferation.

Microglial subtypes: diversity within the microglial community

“…The expression of 5D4‐KSPG in microglia differs significantly between strains of inbred rats (Jander & Stoll, ). In mammals, a subpopulation of 5D4‐KSPG‐expressing microglia was also reported in the spinal cord and retina (Bertolotto et al , , ; Jander & Stoll, ; Jones & Tuszynski, ; Zhang et al , ; Foyez et al , ). The 5D4‐KSPG‐microglia exhibit a preferential regional distribution in the CNS.…”

“…The 5D4‐KSPG‐microglial population described above is influenced by pathology. In particular, 5D4‐KSPG expression is increased selectively in a subset of IBA1/CD11b‐positive microglia in the SOD1 G93A mouse model and human cases of amyotrophic lateral sclerosis (ALS; Hirano et al , ; Foyez et al , ), and in a Wallerian degeneration mouse model of spinal cord injury (Shinjo et al , ), while it decreases in a Guillain–Barré syndrome rat model of experimental autoimmune neuritis (Matsui et al , ). Mice deficient in N‐acetylglucosamine 6‐O‐sulfotransferase‐1 (GlcNAc6ST‐1), an enzyme involved in 5D4‐KSPG biosynthesis, also show reduced 5D4‐KSPG expression in the CNS (Zhang et al , ).…”

“…Mice deficient in N‐acetylglucosamine 6‐O‐sulfotransferase‐1 (GlcNAc6ST‐1), an enzyme involved in 5D4‐KSPG biosynthesis, also show reduced 5D4‐KSPG expression in the CNS (Zhang et al , ). Remarkably, SOD1 G93A GlcNAc6ST‐1 −/− mice exhibit a significantly reduced lifespan and accelerated clinical symptoms as compared to SOD1 G93A mice (Hirano et al , ; Foyez et al , ), suggesting that 5D4‐KSPG‐microglia which expand in SOD1 G93A mice may play a beneficial suppressive role in the early pathogenic phases of ALS (Hirano et al , ).…”

Keratan sulfate (KS)‐proteoglycans and neuronal regulation in health and disease: the importance ofKS‐glycodynamics and interactive capability with neuroregulatory ligands

“…) showing that KS restricts spinal cord repair (Foyez et al . ). GlcNAc6ST‐1 is required for KS biosynthesis in the CNS (Zhang et al .…”

Analysis of circulating protein aggregates reveals pathological hallmarks of amyotrophic lateral sclerosis

“…Four biochemical pathways seemed to represent the most consistent changes at a proteomic level: metabolism of carbohydrates (p= 0.0099), glycosaminoglycans (GAGs) metabolism, lysosome (p= 0.0015), synthesis of phosphatidic acid (p= 0.0184) and wnt signalling pathway (p= 0.0337). It has been shown that GAGs are involved in protein aggregation and prion diffusion ( [36][37][38][39][40][41][42][43][44] ). Lysosome activity changes were described in ALS caused by the C9orf72 gene repeat expansions ( [45][46][47][48][49] ), while synthesis of PA is linked to all types of phospholipids, including phosphatidylcholine and phosphatidylethanolamine that have been linked to ALS and prion disease pathogenesis ( 50,51 ).…”