Abstract
Exposure to solar UV irradiation damages γ-crystallin, leading to cataract formation via aggregation. α-Crystallin, as a small heat shock protein, efficiently suppresses this irreversible aggregation by selectively binding the denatured γ-crystallin monomer. In this study, liquid chromatography tandem mass spectrometry was used to evaluate UV-325 nm irradiation-induced photodamage of human γD-crystallin in the presence of bovine α-crystallin, atomic force microscope (AFM) and dynamic light scattering (DLS) techniques were used to detect the quaternary structure changes of the α-crystallin oligomer, and Fourier transform infrared spectroscopy and temperature-jump nanosecond time-resolved IR absorbance difference spectroscopy were used to probe the secondary structure changes of bovine α-crystallin. We find that the thermal-induced subunit dissociation of the α-crystallin oligomer involves the breaking of hydrogen bonds at the dimeric interface, leading to three different spectral components at varied temperature regions as resolved from temperature-dependent IR spectra. Under UV-325 nm irradiation, unfolded γD-crystallin binds to the dissociated α-crystallin subunit to form an αγ-complex, then follows the reassociation of the αγ-complex to the partially dissociated α-crystallin oligomer. This prevents the aggregation of denatured γD-crystallin. The formation of the γD-bound α-crystallin oligomer is further confirmed by AFM and DLS analysis, which reveals an obvious size expansion in the reassociated αγ-oligomers. In addition, UV-325 nm irradiation causes a peptide bond cleavage of γD-crystallin at Ala158 in the presence of α-crystallin. Our results suggest a very effective protection mechanism for subunits dissociated from α-crystallin oligomers against UV irradiation-induced aggregation of γD-crystallin, at the expense of a loss of a short C-terminal peptide in γD-crystallin.
Original language | English (US) |
---|---|
Pages (from-to) | 2233-2250 |
Number of pages | 18 |
Journal | Biophysical journal |
Volume | 121 |
Issue number | 12 |
DOIs | |
State | Published - Jun 21 2022 |
Bibliographical note
Funding Information:Y.-x.W. and H.L. thank Professor Yong-bin Yan and Doctor Yibo Xi for the Human γD-crystallin sample, Doctor Deyong Li on the T-jump time-resolved IR instrumentation setup, Doctor Haoyi Wang for the programming of the data acquisition system, Doctor Haidi Yin from the Mass Spectrometry Core Facility of Shenzhen Bay Laboratory for mass spectrometry analysis, and Professor Qin Peng for the help in using Nikon NIS-Elements AR software. This work was supported by the National Natural Science Foundation of China (nos. 21433014, 11721404, and 21173012) and the Chinese Academy of Sciences (QYZDJ-SSW-SYS017 and YJKYYQ20170046). The authors declare no competing interests.
Funding Information:
This work was supported by the National Natural Science Foundation of China (nos. 21433014 , 11721404 , and 21173012 ) and the Chinese Academy of Sciences ( QYZDJ-SSW-SYS017 and YJKYYQ20170046 ).
Publisher Copyright:
© 2022 Biophysical Society
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't