Predicted aggregation-prone region (APR) in βB1-crystallin forms the amyloid-like structure and induces aggregation of soluble proteins isolated from human cataractous eye lens

Amyloid Protein Cross-Seeding Provides a New Perspective on Multiple Diseases In Vivo

Amyloid protein cross-seeding is a peculiar phenomenon of cross-spreading among different diseases. Unlike traditional infectious ones, diseases caused by amyloid protein cross-seeding are spread by misfolded proteins instead of pathogens. As a consequence of the interactions among misfolded heterologous proteins or polypeptides, amyloid protein cross-seeding is considered to be the crucial cause of overlapping pathological transmission between various protein misfolding disorders (PMDs) in multiple tissues and cells. Here, we briefly review the phenomenon of cross-seeding among amyloid proteins. As an interesting example worth mentioning, the potential links between the novel coronavirus pneumonia (COVID-19) and some neurodegenerative diseases might be related to the amyloid protein cross-seeding, thus may cause an undesirable trend in the incidence of PMDs around the world. We then summarize the theoretical models as well as the experimental techniques for studying amyloid protein cross-seeding. Finally, we conclude with an outlook on the challenges and opportunities for basic research in this field. Cross-seeding of amyloid opens up a new perspective in our understanding of the process of amyloidogenesis, which is crucial for the development of new treatments for diseases. It is therefore valuable but still challenging to explore the cross-seeding system of amyloid protein as well as to reveal the structural basis and the intricate processes.

Recent progress and research trend of anti-cataract pharmacology therapy: A bibliometric analysis and literature review

Cataract is the leading cause of blindness worldwide. Cataract phacoemulsification combined with intraocular lens implantation causes great burden to global healthcare, especially for low- and middle-income countries. Such burden would be significantly relieved if cataracts can effectively be treated or delayed by non-surgical means. Excitingly, novel drugs have been developed to treat cataracts in recent decades. For example, oxysterols are found to be able to innovatively reverse lens clouding, novel nanotechnology-loaded drugs improve anti-cataract pharmacological effect, and traditional Chinese medicine demonstrates promising therapeutic effects against cataracts. In the present review, we performed bibliometric analysis to provide an overview perspective regarding the research status, hot topics, and academic trends in the field of anti-cataract pharmacology therapy. We further reviewed the curative effects and molecular mechanisms of anti-cataract drugs such as lanosterol, metformin, resveratrol and curcumin, and prospected the possibility of their clinical application in future.

A novel cataract-causing mutation Ile82Met of γA crystallin trends to aggregate with unfolding intermediate

Cataract is the most common pathogenic ophthalmic disease leading to blindness in children worldwide. Genetic disorder is the leading cause of congenital cataract, among which crystallin mutations have a high incidence. There are few reports on γA-crystallin, one critical member of crystallin superfamilies. In this study, we identified a novel pathogenic mutation (Ile82Met) in γA-crystallin from a three-generation Chinese family with cataract, and investigated the potential molecular mechanism in detail. To elucidate the pathogenic mechanism of I82M mutant, spectroscopic and solubility experiments were performed to determine the difference between the purified γA-crystallin wild type (WT) and I82M mutant under both physiological conditions and environmental stresses (UV irradiation, thermal denaturation or chemical denaturation). The I82M mutant did not affect the secondary/tertiary structure of monomeric γA-crystallin under physiological status, but decreased protein stability and increased aggregatory potency under the stressful treatment. Surprisingly, the chemical denaturation caused I82M to switch from the two-state unfolding of γA-crystallin to three-state unfolding involving an unfolding intermediate. This study expands the genetic variation map of cataract, and provides novel insights into the pathomechanism, in particular, filling in a gap in the understanding of γA-crystallin mutants causing cataract.

Pathogenic mechanism of congenital cataract caused by the CRYBA1/A3-G91del variant and related intervention strategies

Congenital cataracts, which are genetically heterogeneous eye disorders, lead to visual impairment in childhood. In our previous study, we identified a novel mutation in exon 4 of the CRYBA1/BA3 gene, which resulted in the deletion of a highly conserved glycine at codon 91 (G91del) and perinuclear zonular cataract. The G91del variant is one of the most frequent pathogenic mutations in CRYBA1/BA3; however, its pathogenic mechanism remains unclear. In this study, we purified βA3-crystallin and the βA3-G91del variant. βA3-G91del was prone to proteolysis and exhibited very low solubility and low structural stability. Next, we constructed a CRYBA1/BA3 mutant cell model and observed that G91del mutant proteins were more sensitive to environmental stress and prone to form aggregates. Size-exclusion chromatography and molecular dynamics simulation showed that the G91del mutation impaired the ability of βA3 to form homo-oligomers. In addition, the protein folding process of βA3-G91del was complicated and showed more intermediate states, resulting in amyloid fiber aggregation and induction of cellular apoptosis. Finally, we investigated intervention strategies for congenital cataract caused by the CRYBA1/A3-G91del variant. The addition of lanosterol reversed the negative effects of the G91del mutation under external stress. This study may help explore potential treatment strategies for related cataracts.

Trehalose Inhibits the Heat-Induced Formation of the Amyloid-Like Structure of Soluble Proteins Isolated from Human Cataract Lens

The age-dependent loss of solubility and aggregation of crystallins constitute the pathological hallmarks of cataract. Several biochemical and biophysical factors are responsible for the reduction of crystallins' solubility and formation of irreversible protein aggregates, which display amyloid-like characteristics. The present study reports the heat-induced aggregation of soluble proteins isolated from human cataract lenses and the formation of amyloid-like structures. Exposure of protein at 55 °C for 4 h resulted in extensive (≈ 60%) protein aggregation. The heat-induced protein aggregates displayed substantial (≈ 20 nm) redshift in the wavelength of maximum absorption (λ_max) of Congo red (CR) and increase in Thioflavin T (ThT) fluorescence emission intensity, indicating the presence of amyloid-like structures in the heat-induced protein aggregates. Subsequently, the addition of trehalose resulted in substantial inhibition of heat-induced aggregation and the formation of amyloid-like structure. The ability of trehalose to inhibit the heat-induced aggregation was found to be linearly dependent upon its concentration used. The optimum effect was observed in the presence of 30-40% (w/v) trehalose where the aggregated was found to be reduced from 60 to 30%. The present study demonstrated the ability to trehalose to inhibit the protein aggregation and interfere with the formation of amyloid-like structures.