Lanosterol reverses protein aggregation in cataracts

Nature 523, 607-611 (30 July 2015)

Ling Zhao, Xiang-Jun Chen, Jie Zhu, Yi-Bo Xi, Xu Yang, Li-Dan Hu, Hong Ouyang, Sherrina H. Patel, Xin Jin, Danni Lin, Frances Wu, Ken Flagg, Huimin Cai, Gen Li, Guiqun Cao, Ying Lin, Daniel Chen, Cindy Wen,

Christopher Chung, Yandong Wang, Austin Qiu, Emily Yeh, Wenqiu Wang, Xun Hu, Seanna Grob, Ruben Abagyan, Zhiguang Su, Harry Christianto Tjondro, Xi-Juan Zhao, Hongrong Luo, Rui Hou,

J. Jefferson, P. Perry, Weiwei Gao, Igor Kozak, David Granet, Yingrui Li, Xiaodong Sun, Jun Wang, Liangfang Zhang, Yizhi Liu, Yong-Bin Yan & Kang Zhang

Katrina A. Diaz

Burke Group Literature Seminar 09/19/15

Cataracts

http://www.mayoclinic.org/diseases-conditions/cataracts/basics/definition/con-20015113

• Age, injury, disease, congenital

• Most common cause of blindness worldwide, affecting tens of millions of people

• By age 80, more than half of all Americans either have a cataract or have had cataract surgery

• Only treatment is cataract surgery, where the cloudy lens is replaced by an artificial intraocular lens

Lens proteins

•  Crystallin proteins in lens fibers contribute to lens transparency and refractive properties

•  α-, β- and γ-crystallins •  Protein aggregation

•  mutations in crystallin proteins (congenital cataracts)

•  oxidative stress (age-related cataracts)

• Destabilization, partial unfolding of the polypeptide chains, population of aggregation-prone intermediates

• Young lenses: α-crystallin effectively recognizes and sequesters these destabilized intermediates

• Age lenses: α-crystallin complexes become saturated with substrate and lens proteins are able to aggregate

Moreau, K. L., & King, J. A. (2012). Protein misfolding and aggregation in cataract disease and prospects for prevention. Trends in molecular medicine, 18(5), 273-282.

Identification of mutations in LSS causing congenital cataracts

Zhao, L., Chen, X. J., Zhu, J., Xi, Y. B., Yang, X., Hu, L. D., ... & Zhang, K. (2015). Lanosterol reverses protein aggregation in cataracts. Nature.

•  Lanosterol synthase is encoded by the LSS gene

•  Catalyzes the conversion of (S)-2,3-oxidosqualene to lanosterol (key early rate-limiting step in the biosynthesis of cholesterol, steroid hormones, and vitamin D)

•  Found to be expressed in the lens •  Previously reported that mutations

on LSS and FDFT1 (farnesyl diphosphate farnesyl transferase could decrease cholesterol levels in the lens and result in cataracts in Shumiya cataract rats (SCR)

LSS mutations abolished the cyclase enzymatic function

Zhao, L., Chen, X. J., Zhu, J., Xi, Y. B., Yang, X., Hu, L. D., ... & Zhang, K. (2015). Lanosterol reverses protein aggregation in cataracts. Nature.

•  W581 and G588 in LSS are highly conserved •  W581 reported to contribute to the catalytic site of the cyclase activity •  G588S (modeled) causes the side chain of the serine to clash into the E578 residue

of the loop and is incompatible with the normal enzymatic structure and function of LSS

•  Neither the W581R nor the G588S mutant protein demonstrated any cyclase activity expressed in HeLa cells

Wild-type LSS significantly reduces both the number and size of intracellular crystallin

aggregates, but LSS mutants cannot

Zhao, L., Chen, X. J., Zhu, J., Xi, Y. B., Yang, X., Hu, L. D., ... & Zhang, K. (2015). Lanosterol reverses protein aggregation in cataracts. Nature.

WT LSS and lanosterol inhibit crystallin mutant aggregation and increase soluble αA-

crystallin(Y118D)

Zhao, L., Chen, X. J., Zhu, J., Xi, Y. B., Yang, X., Hu, L. D., ... & Zhang, K. (2015). Lanosterol reverses protein aggregation in cataracts. Nature.

Lanosterol inhibits crystallin mutant aggregation and increase soluble αA-crystallin(Y118D)

Zhao, L., Chen, X. J., Zhu, J., Xi, Y. B., Yang, X., Hu, L. D., ... & Zhang, K. (2015). Lanosterol reverses protein aggregation in cataracts. Nature.

Lanosterol inhibits crystallin mutant aggregation in human lens progenitor cells

Zhao, L., Chen, X. J., Zhu, J., Xi, Y. B., Yang, X., Hu, L. D., ... & Zhang, K. (2015). Lanosterol reverses protein aggregation in cataracts. Nature.

Lanosterol re-dissolved pre-formed amyloid-like fibrils of crystallin proteins

Zhao, L., Chen, X. J., Zhu, J., Xi, Y. B., Yang, X., Hu, L. D., ... & Zhang, K. (2015). Lanosterol reverses protein aggregation in cataracts. Nature.

Lanosterol reduced cataract severity and increased clarity

Zhao, L., Chen, X. J., Zhu, J., Xi, Y. B., Yang, X., Hu, L. D., ... & Zhang, K. (2015). Lanosterol reverses protein aggregation in cataracts. Nature.

Conclusions and Future Directions •  Homozygous mutations affecting the catalytic function of

LSS cause extensive congenital cataracts with severe vision loss

•  Lanosterol treatment both decreased protein aggregation caused by mutant crystallin proteins in cell culture and reduced preformed cataract severity by increasing lens clarity in animal models

•  Potential strategy for the prevention and treatment of cataracts

•  May have broader implications for the treatment of protein-aggregation diseases, including neurodegenerative diseases and diabetes