Evolutionary diversity of social amoebae N-glycomes may support interspecific autonomy

Abstract

Multiple species of cellular slime mold (CSM) amoebae share overlapping subterranean environments near the soil surface. Despite similar life-styles, individual species form independent starvation-induced fruiting bodies whose spores can renew the life cycle. N-glycans associated with the cell surface glycocalyx have been predicted to contribute to interspecific avoidance, resistance to pathogens, and prey preference. N-glycans from five CSM species that diverged 300–600 million years ago and whose genomes have been sequenced were fractionated into neutral and acidic pools and profiled by MALDI-TOF-MS. Glycan structure models were refined using linkage specific antibodies, exoglycosidase digestions, MALDI-MS/MS, and chromatographic studies. Amoebae of the type species Dictyostelium discoideum express modestly trimmed high mannose N-glycans variably modified with core α3-linked Fuc and peripherally decorated with 0–2 residues each of β-GlcNAc, Fuc, methylphosphate and/or sulfate, as reported previously. Comparative analyses of D. purpureum, D. fasciculatum, Polysphondylium pallidum, and Actyostelium subglobosum revealed that each displays a distinctive spectrum of high-mannose species with quantitative variations in the extent of these modifications, and qualitative differences including retention of Glc, mannose methylation, and absence of a peripheral GlcNAc, fucosylation, or sulfation. Starvation-induced development modifies the pattern in all species but, except for universally observed increased mannose-trimming, the N-glycans do not converge to a common profile. Correlations with glycogene repertoires will enable future reverse genetic studies to eliminate N-glycomic differences to test their functions in interspecific relations and pathogen evasion.

Diversity-Generating Machines: Genetics of Bacterial Sugar-Coating

“…The specificity of such recognitions between a bacterivorous amoeba, Acanthamoeba castellanii , and E. coli has been attributed to the interaction between LPS and the predator’s surface mannose-binding protein [92] . Given the genetically characterised diversity of mannose N-glycans between different species of amoebae [93] , it is plausible that such interactions have shaped (at least partly) the diversity of O-antigens in some bacteria, as has been argued previously [64] .…”

Hydrophilic interaction anion exchange for separation of multiply modified neutral and anionic Dictyostelium N‐glycans

“…The cumulative data indicate that phosphate residues, whether unsubstituted or as HexNAc-or methyl-diesters, tend to be on terminal mannose residues, whereas sulphate is generally a subterminal substitution. The methyl residues are only associated with phosphate and not with hexose as is the case in the distantly related social amoeba Polysphondylium pallidum [11].…”

“…Basic features such as the presence of intersecting N‐ acetylglucosamine, methylphosphate, and sulphate on oligomannose‐type N‐glycans of the slime mould were shown by a number of methods such as anion exchange, normal phase, lectin affinity, and gel filtration chromatography of radiolabeled glycans, solvolysis, MS, and/or nuclear magnetic resonance (see, e.g. ); nevertheless proof of the actual structures of many neutral and anionic N‐glycans derived from either wild‐type or mutant strains was only possible after more recent developments in MS .…”

“…Hex 8,10-11 HexNAc 2-4 -based sulphated or (methyl)phosphorylated structures which coelute with those based on Hex 9 HexNAc 2 are shown in a greyscale; asterisks in panel A indicate contaminants of m/z 2154 and 2220. The parent structures, but not the in source fragment ions, are annotated with the composition (as H[8][9][10][11] N 2-4 P 0-1 Me 0-1 S 0-3 ; i.e.Hex[8][9][10][11] HexNAc 2-4 P 0-1 Me 0-1 S 0-3 ); in source losses of sulphate are indicated by ⌬ 102 or 118 (i.e. loss of sulphate and sodium or potassium counterions), whereas loss of mannose residues upon enzymatic digestion are indicated by red or blue dashed lines.…”

Enabling tools forToxoplasmaglycobiology

“…The range and abundance of Toxoplasma glycan classes, as profiled by mass spectrometry and including findings from radiolabeling, mAb and lectin studies, is more than initially appreciated but relatively limited compared to other protozoans such as trypanosomatid parasites and the amoebozoan Dictyostelium Sucgang et al, 2011;Feasley et al, 2015;Schiller et al, 2012). Furthermore, there is notable lack of known anionic modifications of Toxoplasma glycans that are prominent elsewhere in the form of anionic sugars or substitutions with PO4 or SO4.…”