Site-specific O-glycans influence lacritin structure and multimerization in tears

Area of Science:

• Biochemistry
• Glycobiology
• Ocular Surface Science

Background:

• Lacritin, a tear glycoprotein, is vital for ocular surface health, immune response, and bacterial defense.
• Its functions are regulated by mechanisms like multimerization, but the role of its extensive O-glycans is unclear.
• Lacritin is a potential biomarker and therapeutic for dry eye disease (DED).

Purpose of the Study:

• To investigate the structural role of site-specific O-glycans on C-terminal lacritin using glycoproteomics and molecular dynamics.
• To understand how O-glycans influence lacritin's structure, multimerization, and biological activity.

Main Methods:

• Mass spectrometry (MS)-based glycoproteomics to profile glycosylation.
• Molecular dynamics (MD) simulations to analyze glycoform structures.
• Quantification of solvent-accessible surface area (SASA) for key residues.

Main Results:

• Distinct glycosylation profiles were found between monomeric and multimeric lacritin.
• O-glycans influence lacritin's conformational flexibility and the spatial arrangement of crosslinking residues (Lys101, Lys104).
• Proximal O-glycosylation near Lys101 and Lys104 affects their propensity for crosslinking.

Conclusions:

• Lacritin's O-glycans play a crucial role in its structural topology.
• Glycan modifications impact lacritin's ability to form multimers and influence its biological functions.
• Understanding these glycan-protein interactions is key for lacritin's therapeutic potential in DED.