title: Characterization of the cellular uptake and metabolic conversion of acetylated N-acetylmannosamine (ManNAc) analogues to sialic acids.
abstract: "Sialic acid engineering" refers to the strategy where cell surface carbohydrates are modified by the biosynthetic incorporation of metabolic intermediates, such as non-natural N-acetylmannosamine (ManNAc) analogues, into cellular glycoconjugates. While this technology has promising research, biomedical, and biotechnological applications due to its ability to endow the cell surface with novel physical and chemical properties, its adoption on a large scale is hindered by the inefficient metabolic utilization of ManNAc analogues. We address this limitation by proposing the use of acetylated ManNAc analogues for sialic acid engineering applications. In this paper, the metabolic flux of these "second-generation" compounds into a cell, and, subsequently, into the target sialic acid biosynthetic pathway is characterized in detail. We show that acetylated ManNAc analogues are metabolized up to 900-fold more efficiently than their natural counterparts. The acetylated compounds, however, decrease cell viability under certain culture conditions. To determine if these toxic side effects can be avoided, we developed an assay to measure the cellular uptake of acetylated ManNAc from the culture medium and its subsequent flux into sialic acid biosynthetic pathway. This assay shows that the majority ( > 80%) of acetylated ManNAc is stored in a cellular "reservoir" capable of safely sequestering this analogue. These results provide conditions that, from a practical perspective, enable the acetylated analogues to be used safely and efficaciously and therefore offer a general strategy to facilitate metabolic substrate-based carbohydrate engineering efforts. In addition, these results provide fundamental new insights into the metabolic processing of non-natural monosaccharides.
authors.affiliation: Department of Biomedical Engineering and the G.W.C. Whiting School of Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Mark B
authors.initials: MB
authors.lastname: Jones
authors.forename: Howard
authors.initials: H
authors.lastname: Teng
authors.forename: Jun Kyu
authors.initials: JK
authors.lastname: Rhee
authors.forename: Nicholas
authors.initials: N
authors.lastname: Lahar
authors.forename: Gautam
authors.initials: G
authors.lastname: Baskaran
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Yarema
mesh_terms: D000107:Acetylation; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D016466:CHO Cells; D019556:COS Cells; D002455:Cell Division / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology*; D002522:Chlorocebus aethiops; D006224:Cricetinae; D003412:Cricetulus; D003470:Culture Media; D017077:Culture Media, Conditioned / Q000378:metabolism; D006367:HeLa Cells; D006595:Hexosamines / Q000493:pharmacokinetics*; D006801:Humans; D019169:Jurkat Cells; D008657:Metabolic Clearance Rate; D012794:Sialic Acids / Q000096:biosynthesis*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D003470:Culture Media; D017077:Culture Media, Conditioned; D006595:Hexosamines; D012794:Sialic Acids; C002022:N-acetylmannosamine