Cataract-causing G91del mutant destabilised βA3 heteromers formation linking with structural stability and cellular...

Area of Science:

• Ophthalmology
• Molecular Biology
• Biochemistry

Background:

• Congenital cataracts cause childhood visual impairment globally.
• BetaA3-crystallin (CRYBA1/BA3) is crucial for lens transparency, forming homomers and heteromers.
• A previously identified mutation, G91del, leads to perinuclear zonular cataracts.

Purpose of the Study:

• To elucidate the pathogenic mechanism of the G91del mutation in betaA3-crystallin.
• To investigate the mutation's impact on protein structure, heteromer formation, and cellular function.

Main Methods:

• Protein purification, size-exclusion chromatography, spectroscopy, and molecular dynamics simulations.
• Assays for heteromer formation, protein structural properties, and cellular functions including MTT and apoptosis assays.
• In vitro studies involving intracellular overexpression of wild-type and mutant betaA3-crystallin.

Main Results:

• BetaA3/betaB2 heteromers exhibit enhanced stability compared to betaA3 homomers.
• The G91del mutation disrupts betaA3-crystallin interaction with betaB2-crystallin, reducing structural stability and stress resistance.
• Mutant betaA3-G91del induces cellular apoptosis and loses protection from betaB2-crystallin.

Conclusions:

• BetaA3/betaB2 heteromers are essential for maintaining lens transparency.
• The G91del mutation destabilizes these heteromers, impairs cellular viability, and induces apoptosis, contributing to cataract development.