Principal Investigator: Kenji Uchimura
Grant Title: Regulation of amyloid clearance by heparan sulfate remodeling
Abstract:
Protein aggregation diseases represent one of the most compelling research subjects both inprotein chemistry and molecular medicine. Amyloid known as tissue deposits of protein
aggregates causes protein aggregation diseases. Amyloid in tissues is cleared by innate immune
phagocytes such as microglia in the brain and macrophages in the peripheral tissues.
Conversely, impairment of the cellular clearance leads to excess of deposits and diseaseprogression. Alzheimer’s disease (AD) is a brain-type protein aggregation disease. A multitudeof studies have shown that heparan sulfate (HS) interacts with aggregation-prone peptides,including Amyloid ß (Aß) and tau in AD, and coexists as a non-protein component in deposits
of protein aggregates in AD brains (1). HS in amyloid deposits is involved in inhibition ofcellular clearance of amyloid by forming a protective shield around them. We previously
showed that S-domains, highly sulfated domains of HS composed of IdoA2S-GlcNS6S units,
are accumulated in tissue amyloid of model mice and patients with AD. We also showed thatremoval of the sulfate group at position 6 of S-domains by Sulf2, an extracellular sulfatase,facilitated microglial clearance of amyloid ex vivo. The aim of this study is to evaluate
mitigation effects of Sulf2 on AD brain pathogenesis in vivo.
Sulf2 conditional transgenic mouse models that allow cell type-specific expression of thehuman Sulf2 gene were generated. These mice were bred with an activated microglia-specificCre-driver and then crossbred with J20 AD model mice (2). We currently analyze the degreeof amyloid deposits and AD pathogenesis in the brain of these mice with age. Microglial
clearance of Aß amyloid may be facilitated by the Sulf2 action in AD brain. On the other hand,
we utilized chemically synthesized 6-O-phosphorylated HS oligosaccharide derivatives toanalyze possible roles of C-6 sulfate groups of the S-domains in Aβ aggregation (3). We tested
them for assays of Aβ fibril formation. Compounds 30 and 38 showed inhibitory effects on Aβfibril formation in the presence of heparin, a structural analogue of HS S-domains, as measured
by the ThT fluorescence intensities and studied by atomic force microscopy (3). Upon
aggregation the transition of an unstructured state to a β-sheet structure can create sulfated
GAG-binding sites. Compounds 30 and 38 may bind to these conformers and interfere with thesubsequent elongation process. These small sulfated and phosphorylated HS glycans may beutilized in vivo with AD models in future challenge. The transgenic model mice would also
aide to investigate potential roles of post-translational modifications of Sulf2 (4) in its
biological functions in vivo. The Sulf2 project will be extended to study prion-like behavior of
p53 aggregates (5).
1) Nishitsuji K & Uchimura K. Sulfated glycosaminoglycans in protein aggregation diseases. Glycoconj J(34):453-466, 2017.
2) Zhang Z, Takeda-Uchimura Y, Foyez T, Ohtake-Niimi S, Narentuya, Akatsu H, Nishitsuji K, Michikawa M,Wyss-Coray T, Kadomatsu K & Uchimura. Deficiency of a sulfotransferase for sialic acid-modified glycans
mitigates Alzheimer's pathology. Proc Natl Acad Sci USA (114):E2947-E2954, 2017.
3) Uchimura K, Nishitsuji K, Chiu LT, Ohgita T, Saito H, Allain F, Gannedi V, Wong CH & Hung SC. Designand synthesis of 6-O-phosphorylated heparan sulfate oligosaccharides to inhibit amyloid ß aggregation.
ChemBioChem (23):e202200191, 2022.
4) El Masri R, Seffouh A, Roelants C, Seffouh I, Gout E, Pérard J, Dalonneau F, Nishitsuji K, Noborn F, Nikpour
M, Larson G, Crétinon Y, Friedel-Arboleas M, Uchimura K, Daniel R, Lortat-Jacob H, Filhol O & Vivés RR.
Extracellular endosulfatase Sulf-2 harbors a chondroitin/dermatan sulfate chain that modulates ist enzymatic
activity. Cell Rep (38):110516, 2022.
5) Iwahashi N, Ikezaki M, Nishikawa T, Namba N, Ohgita T, Saito H, Ihara Y, Shimanouchi T, Ino K, Uchimura
K & Nishitsuji K. Sulfated glycosaminoglycans mediate prion-like behavior of p53 aggregates. Proc NatlAcad Sci USA (117):33225-33234, 2020.