Uncommon N-Glycan Structures in Anhydrobiotic Tardigrades

Area of Science:

• Glycobiology
• Tardigrade Biology
• Extremophile Research

Background:

• N-glycosylation plays vital roles in protein function and stability.
• Tardigrades exhibit remarkable resilience to extreme environmental conditions, but the underlying molecular mechanisms are not fully understood.
• Glycosylation patterns can be critical for stress adaptation in various organisms.

Purpose of the Study:

• To characterize the N-glycosylation profiles of anhydrobiotic tardigrades, Ramazzottius varieornatus and Hypsibius exemplaris.
• To identify unique glycosylation signatures and their potential roles in tardigrade stress tolerance.
• To investigate the enzymatic machinery potentially responsible for observed glycosylation patterns.

Main Methods:

• Mass spectrometry-based glycomic analysis of N-glycans from tardigrade species.
• Identification and quantification of different N-glycan structures, including fucosylation patterns.
• Comparative analysis of tardigrade glycosylation with other species.
• Genomic analysis to identify potential fucosyltransferase genes.

Main Results:

• Tardigrades exhibit high-mannose, paucimannose, and complex-type N-glycans; hybrid-type glycans were absent.
• Paucimannose glycans were abundant (39% in R. varieornatus, 17% in H. exemplaris), with significant core fucosylation.
• A unique glycosylation signature with non-reducing terminal α1,3-fucosylated N-acetylglucosamine (GlcNAc) was identified, particularly in H. exemplaris, and induced during anhydrobiosis.
• Key proteins like Cu/Zn-superoxide dismutase were modified with this unique glycan structure.
• Tardigrade fucosylation patterns differ from mammalian and other invertebrate structures, suggesting unique fucosyltransferase specificities.

Conclusions:

• Tardigrades possess distinct N-glycosylation profiles characterized by abundant paucimannose and unique fucosylation patterns.
• The identified α1,3-fucosylated GlcNAc motif may contribute to tardigrade stress tolerance mechanisms.
• Homologs of FUT9 and FucTC suggest potential enzymes responsible for this unique glycosylation.
• Further research into tardigrade glycosylation can illuminate mechanisms of extremotolerance.