Laminins in an in vitro anterior lens capsule model established using HLE B-3 cells

The novel mutation P36R in LRP5L contributes to congenital membranous cataract via inhibition of laminin γ1 and c-MAF

PURPOSE

The present study investigated a pathogenic mutation and its mechanism on membranous cataract in a congenital membranous cataract family.

METHODS

An autosomal dominant four-generation Chinese congenital membranous cataract family was recruited and whole-exome sequencing was performed to screen for sequence variants. Candidate variants were validated using polymerase chain reaction and Sanger sequencing. Wild-type and mutant low-density lipoprotein receptor-related protein 5-like (LRP5L) plasmids were constructed and transfected into human lens epithelial cells (HLE B-3) and human anterior lens capsules. The cell lysates, nuclear and cytoplasmic proteins, and basement membrane components of HLE B-3 cells were harvested. LRP5L and laminin γ1 were knocked down in HLE B-3 cells using specific small-interfering RNA. The protein expression levels of LRP5L, laminin γ1, and c-MAF were detected using immunoblotting and immunofluorescence.

RESULTS

We identified a novel suspected pathogenic mutation in LRP5L (c.107C > G, p.P36R) in the congenital membranous cataract family. This mutation was absent in 300 normal controls and 300 age-related cataract patients. Bioinformatics analysis with PolyPhen-2 and SIFT suggested that LRP5L-P36R was pathogenic. LRP5L upregulated laminin γ1 expression in the cytoplasmic proteins of HLE B-3 cells and human anterior lens capsules, and LRP5L-P36R inhibited the effects of LRP5L. LRP5L upregulated c-MAF expression in the nucleus and cytoplasm of HLE B-3 cells, and LRP5L-P36R inhibited c-MAF expression via inhibition of laminin γ1.

CONCLUSION

Our study identified a novel gene, LRP5L, associated with congenital membranous cataract, and its mutant LRP5L-P36R contributed to membranous cataract development via inhibition of laminin γ1 and c-MAF.

Laminin α4 overexpression in the anterior lens capsule may contribute to the senescence of human lens epithelial cells in age-related cataract

Senescence is a leading cause of age-related cataract (ARC). The current study indicated that the senescence-associated protein, p53, total laminin (LM), LMα4, and transforming growth factor-beta1 (TGF-β1) in the cataractous anterior lens capsules (ALCs) increase with the grades of ARC. In cataractous ALCs, patient age, total LM, LMα4, TGF-β1, were all positively correlated with p53. In lens epithelial cell (HLE B-3) senescence models, matrix metalloproteinase-9 (MMP-9) alleviated senescence by decreasing the expression of total LM and LMα4; TGF-β1 induced senescence by increasing the expression of total LM and LMα4. Furthermore, MMP-9 silencing increased p-p38 and LMα4 expression; anti-LMα4 globular domain antibody alleviated senescence by decreasing the expression of p-p38 and LMα4; pharmacological inhibition of p38 MAPK signaling alleviated senescence by decreasing the expression of LMα4. Finally, in cataractous ALCs, positive correlations were found between LMα4 and total LM, as well as between LMα4 and TGF-β1. Taken together, our results implied that the elevated LMα4, which was possibly caused by the decreased MMP-9, increased TGF-β1 and activated p38 MAPK signaling during senescence, leading to the development of ARC. LMα4 and its regulatory factors show potential as targets for drug development for prevention and treatment of ARC.