Chemical and Chemo-Enzymatic Syntheses of Glycans Containing Ribitol Phosphate Scaffolding of Matriglycan

Abstract

Ribitol phosphate modifications to the core M3 O-mannosyl glycan are important for the functional maturation of α-dystroglycan. Three sequentially extended partial structures of the core M3 O-mannosyl glycan including a tandem ribitol phosphate were regio- and stereo-selectively synthesized: Rbo5P-3GalNAcβ, Rbo5P-1Rbo5P-3GalNAcβ, and Xylβ1-4Rbo5P-1Rbo5P-3GalNAcβ (Rbo5P, d-ribitol-5-phosphate; GalNAc, N-acetyl-d-galactosamine; Xyl, d-xylose). Rbo5P-3GalNAcβ with p-nitrophenyl at the aglycon part served as a substrate for ribitol phosphate transferase (FKRP, fukutin-related protein), and its product was glycosylated by the actions of a series of glycosyltransferases, namely, ribitol xylosyltransferase 1 (RXYLT1), β1,4-glucuronyltransferase 1 (B4GAT1), and like-acetyl-glucosaminyltransferase (LARGE). Rbo5P-3GalNAcβ equipped with an alkyne-type aglycon was also active for FKRP. The molecular information obtained on FKRP suggests that Rbo5P-3GalNAcβ derivatives are the minimal units required as the acceptor glycan for Rbo5P transfer and may serve as a precursor for the elongation of the core M3 O-mannosyl glycan.

Synthesis of Core M3 Matriglycan Constituents via an Additive-Controlled 1,2-cis-Xylopyranosylation with O-Xylosyl Imidates as Donors

“…14,15 Toward a better under-standing of the biological and correlated pathological events, which may lead to precise identification and potential interrogation of the disease process, 16 the construction of structure-defined matriglycan derivatives gained much research interest. 17,18 Recently, we developed a chemoenzymatic approach to assemble core M1, core M2, and core M3 O-mannosyl glycopeptides. 19 Hence, various efforts were devoted to the development of α-selective xylosidation methods in the past decades (Figure 2).…”

“…The xyloglucosyl trisaccharide, α- d -Xyl p (1→3)-α- d -Xyl p (1→3)-β- d -Glc p -(1→)- l -Ser, is an important PTM in various proteins with regard to cell signaling, such as epidermal growth factor (EGF) domains of bovine blood-clotting factors, , protein Z, and notch receptors . Recently, matriglycan (Figure ), composed of a repetitive disaccharide unit with the alternative linkage of α-xylopyranoside and β-glucuronic acid [α- d -Xyl p- (1→3)-β- d -GlcA p -(1→3)-] n , is found as an extension of the core M3 O -mannosyl glycans on α-dystroglycan (α-DG), − through the linkage of tandem repeating units of ribitol phosphates. , As matriglycan serves as a scaffold for the binding of various extracellular matrix (ECM) proteins, such as laminin, agrin, and perlecan, it is actively engaged in various cellular events such as muscle and brain development, , tumor mutagenesis, and pathogen infection. , Toward a better understanding of the biological and correlated pathological events, which may lead to precise identification and potential interrogation of the disease process, the construction of structure-defined matriglycan derivatives gained much research interest. , …”