Deamidation Promotes AGE-Modifications in Human Lens γS-Crystallin

Area of Science:

• Biochemistry
• Ophthalmology
• Protein Chemistry

Background:

• Deamidation and advanced glycation end products (AGEs) are key post-translational modifications (PTMs) in eye lens proteins.
• These PTMs contribute to protein aggregation, light scattering, lens aging, and cataract formation.
• The interplay between deamidation and AGE formation remains poorly understood.

Purpose of the Study:

• To investigate the relationship between deamidation and AGE formation in gamma-S-crystallin (γSC).
• To determine how deamidation affects AGE accumulation and cross-linking in γSC.
• To explore the combined effects of deamidation and oxidation on AGE formation in γSC.

Main Methods:

• Mimicked deamidation in γSC by mutating asparagine residues to aspartic acid.
• Incubated deamidation mimics with a glycating mixture.
• Evaluated AGE formation using Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS).
• Investigated the impact of oxidation (GSSG) on deamidated γSC.

Main Results:

• Deamidation significantly promoted the formation of both non-cross-linking and cross-linking AGEs in lysine residues of γSC.
• Deamidated γSC variants (N14D, N143D, triple deamidated) showed higher AGE accumulation than native γSC.
• Oxidation of deamidated γSC further increased AGE formation, indicating heightened susceptibility.

Conclusions:

• Deamidation acts as a catalyst for AGE formation in γSC.
• Oxidation exacerbates AGE modifications in deamidated γSC.
• The synergistic effects of deamidation, oxidation, and AGEs likely drive protein cross-linking and aggregation in age-related cataracts.