Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand.
Published: April 2016
AI Article Synopsis
Article Abstract
The majority of lysosomal enzymes are targeted to the lysosome by post-translational tagging with N-glycans terminating in mannose-6-phosphate (M6P) residues. Some current enzyme replacement therapies (ERTs) for lysosomal storage disorders are limited in their efficacy by the extent to which the recombinant enzymes bear the M6P-terminated glycans required for effective trafficking. Chemical synthesis was combined with endo-β-N-acetylglucosaminidase (ENGase) catalysis to allow the convergent synthesis of glycosyl amino acids bearing M6P residues. This approach can be extended to the remodeling of proteins, as exemplified by RNase. The powerful synergy of chemical synthesis and ENGase-mediated biocatalysis enabled the first synthesis of a glycoprotein bearing M6P-terminated N-glycans in which the glycans are attached to the peptide backbone by entirely natural linkages.
The cation-independent mannose 6-phosphate receptor (CI-MPR) is clinically significant in the treatment of patients with lysosomal storage diseases because it functions in the biogenesis of lysosomes by transporting mannose 6-phosphate (M6P)-containing lysosomal enzymes to endosomal compartments. CI-MPR is multifunctional and modulates embryonic growth and fetal size by downregulating circulating levels of the peptide hormone insulin-like growth factor 2 (IGF2). The extracellular region of CI-MPR comprises 15 homologous domains with binding sites for M6P-containing ligands located in domains 3, 5, 9, and 15, whereas IGF2 interacts with residues in domain 11.
Department of Medicinal Biotechnology, Institute for Medicinal Biotechnology, Graduate School of Pharmaceutical Sciences, Tokushima University, Tokushima, Japan.
Neuraminidase 1 (NEU1) is a lysosomal sialidase that cleaves terminal α-linked sialic acid residues from sialylglycans. NEU1 is biosynthesized in the rough endoplasmic reticulum (RER) lumen as an N-glycosylated protein to associate with its protective protein/cathepsin A (CTSA) and then form a lysosomal multienzyme complex (LMC) also containing β-galactosidase 1 (GLB1). Unlike other mammalian sialidases, including NEU2 to NEU4, NEU1 transport to lysosomes requires association of NEU1 with CTSA, binding of the CTSA carrying terminal mannose 6-phosphate (M6P)-type N-glycan with M6P receptor (M6PR), and intralysosomal NEU1 activation at acidic pH.
Department of Medicinal Biotechnology, Institute for Medicinal Research, Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78-1, Shoumachi, Tokushima-shi, Tokushima 770-8505, Japan.
Many lysosomal enzymes contain N-glycans carrying mannose 6-phosphate (M6P) residues. Modifying lysosomal enzymes by M6P residues requires a two-step process in the Golgi apparatus. Then the lysosomal enzymes with M6P residues are transported from the trans-Golgi network to endosomes and lysosomes by M6P receptors.
β-Cyclodextrin (β-CD) and derivatives are approved therapeutics in >30 clinical settings. β-CDs have also shown promise as therapeutics for treatment of some lysosomal storage disorders, such as Niemann-Pick disease type C, and other disease states which involve metabolite accumulation in the lysosome. In these cases, β-CD activity relies on transport to the lysosome, wherein it can bind hydrophobic substrate and effect extraction.
The spike (S) protein plays a key role in COVID-19 (SARS-CoV-2) infection and host-cell entry. Previous studies have systematically analyzed site-specific glycan compositions as well as many important structural motifs of the S protein. Here, we further provide structural-clear glycosylation of the S protein at a site-specific level by using our recently developed structural- and site-specific glycoproteomics sequencing algorithm, StrucGP.
