Lens Capsule Proteomics Reveals Lysosomal Breakdown Linking Cataract and Glaucoma

The lens of the eye has long been treated as a passive bystander in glaucoma, a disease defined by the slow, insidious death of retinal nerve fibers under elevated pressure inside the eye. A new study published in the Journal of Translational Medicine challenges that assumption by mapping, in unprecedented molecular detail, what happens to the anterior lens capsule — the thin, transparent basement membrane that envelops the lens — when age-related cataract coincides with primary angle-closure glaucoma. The researchers, led by Jiamiao Liu, Rong Rong, Lexi Ding, and Xiaobo Xia of the Eye Center of Xiangya Hospital at Central South University in Changsha, China, report that capsules from patients with both conditions carry a distinctive protein signature centered on a single, unexpected culprit: ATP6V1A, a critical subunit of the cellular acidification machinery.

Primary angle-closure glaucoma, or PACG, is particularly prevalent in East Asian populations and arises when the iris physically blocks the drainage angle of the eye, driving up intraocular pressure. Because the lens sits directly behind the iris and a thickened or enlarged lens can itself promote closure of the angle, ophthalmologists have suspected for decades that lens biology and PACG are intertwined. What has been missing is a molecular account of that relationship. The anterior lens capsule is not merely packaging; it is a biologically active interface through which nutrients, signaling molecules, and waste products pass, and it houses the lens epithelial cells that maintain lens transparency throughout life. Until now, its protein landscape in PACG had remained essentially uncharted.

To build that map, the team turned to data-independent acquisition mass spectrometry, a proteomic technique that systematically measures thousands of proteins in a sample with high reproducibility. They compared anterior lens capsule specimens from patients undergoing cataract surgery who had age-related cataract alone against those who had cataract combined with PACG. After rigorous quality control, the analysis included 13 capsules from the cataract-only group and 10 from the PACG group. The comparison yielded a striking result: 1,262 proteins were differentially expressed between the two conditions, a scale of molecular remodeling far beyond what anyone had anticipated in this thin sheet of tissue.

The direction of the changes proved as informative as their number. Proteins that were reduced in PACG-associated capsules were enriched for networks governing proteostasis — the cell’s system for maintaining properly folded, functional proteins — including molecular chaperones and the neddylation pathway, a modification cascade that regulates protein degradation machinery. When the researchers ran these depleted proteins through enrichment and protein-protein interaction network analyses, they converged on a common hub: lysosome-related dysfunction. Lysosomes are the cell’s acidic recycling compartments, and their proper function depends on the vacuolar-type H+-ATPase, or V-ATPase, the proton pump that acidifies them. In the PACG capsules, ATP6V1A — a major subunit of that pump — was coordinately decreased alongside additional V-ATPase subunits, the lysosomal membrane protein LAMP2, and members of the Rag GTPase family, which regulate lysosomal signaling and nutrient sensing.

On the other side of the ledger, proteins that were increased in the PACG capsules were enriched for extracellular matrix remodeling and lipid and glycan metabolic pathways. That pattern suggests the capsule in PACG eyes is not simply degenerating; it is actively restructuring, with potential consequences for the mechanical relationships between the lens, iris, and drainage angle that define angle-closure disease. The researchers also performed receiver operating characteristic analyses to evaluate how well the differential proteins distinguished the two patient groups, an early step toward assessing whether such markers could eventually support clinical classification.

A single proteomic comparison, however compelling, cannot establish mechanism. So the team pursued ATP6V1A through an unusually thorough series of validation experiments. They confirmed reduced ATP6V1A in human anterior lens capsule flat mounts — whole-mount preparations that preserve the spatial architecture of the tissue. They then applied pressure stress to lens epithelial cells in culture, mimicking the mechanical environment of elevated intraocular pressure, and again observed ATP6V1A reduction. Retinal stress models, including ischemia-reperfusion paradigms, reproduced the signal, and — critically — so did peripheral blood mononuclear cells drawn from an additional small clinical cohort of patients with PACG. The consistency of the ATP6V1A decrease across human tissue, cell culture, animal models, and circulating immune cells lent substantial weight to the finding.

To test whether the loss of this proton pump actually matters functionally, the researchers used pharmacologic inhibition of the V-ATPase. The result was telling: disrupting the pump disturbed lysosomal homeostasis before any overt loss of cell viability could be detected. In other words, lysosomal dysfunction is not merely a late consequence of dying cells; it is an early event that precedes cell death, positioning it as a plausible upstream driver of lens epithelial injury rather than a passive byproduct. This temporal ordering is what elevates ATP6V1A from a correlational marker to a candidate mechanistic link between elevated intraocular pressure, lens epithelial damage, and the coexistence of PACG with age-related cataract.

The study also looked outward, to an independent population-scale dataset. The team examined an exploratory plasma proteomic dataset from the UK Biobank, a large-scale biomedical resource containing health data from hundreds of thousands of participants. Notably, the ATP6V1A signal itself did not reappear in circulating plasma, a reminder that tissue-resident protein changes do not always translate to the bloodstream and that plasma proteomics has inherent limitations for detecting organ-specific molecular events. Yet the UK Biobank analysis did provide external support for glaucoma-associated lens-related and metabolic alterations, independently corroborating the broader biological themes — if not the specific protein — that emerged from the capsule analysis.

The implications reach in several directions at once. Clinically, the findings suggest that the lens capsule could serve as a readout of molecular stress in glaucoma, and that ATP6V1A-associated lysosomal dysfunction might eventually inform how ophthalmologists understand and stratify patients whose cataract and glaucoma travel together. Mechanistically, the work reframes the lens as an active participant in PACG pathogenesis: pressure stress appears to erode the very machinery that lens epithelial cells need to recycle damaged proteins and maintain transparency, and that erosion is detectable in the capsule before cells die. If lysosomal failure is indeed an early, targetable event, it opens a conceptual window for interventions aimed at preserving proteostasis in the stressed lens — though the authors are careful to frame ATP6V1A as a candidate link, not a proven therapeutic target.

There are, of course, limits to what any single study can establish. The clinical cohorts were small — 13 and 10 capsules in the primary comparison, plus a modest validation cohort — and the UK Biobank plasma analysis failed to recapitulate the central signal. The study was conducted in accordance with the Declaration of Helsinki, approved by the Ethics Committee of Xiangya Hospital, and registered with the Chinese Clinical Trial Registry, with animal work separately approved by the institution’s animal care committee, but replication in larger and more diverse populations will be essential before these molecular signatures enter clinical practice. Even so, the scale of the proteomic remodeling documented here — more than 1,200 differential proteins converging on a single lysosomal hub — makes a persuasive case that the anterior lens capsule has been telling a molecular story all along, and that researchers are only now learning to read it. For the millions of people, particularly across Asia, who face the double burden of cataract and angle-closure glaucoma, that story may ultimately point toward new ways of protecting both the clarity of the lens and the survival of the sight it helps deliver.

Subject of Research: Proteomic identification of ATP6V1A-associated lysosomal dysregulation in the anterior lens capsule in age-related cataract with primary angle-closure glaucoma

Article Title: Comparative proteomics of human anterior lens capsules reveals ATP6V1A-associated lysosomal dysregulation in age-related cataract with primary angle-closure glaucoma

Article References: Liu, J., Wang, J., Zeng, Y., Zhao, Z., Zhu, P., Liu, Y., Dong, Q., Zhao, J., Xia, X., Rong, R., & Ding, L. (2026). Comparative proteomics of human anterior lens capsules reveals ATP6V1A-associated lysosomal dysregulation in age-related cataract with primary angle-closure glaucoma. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08934-0

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08934-0

Keywords: primary angle-closure glaucoma, age-related cataract, anterior lens capsule, proteomics, ATP6V1A, lysosomal dysfunction, V-ATPase, lens epithelial cells, intraocular pressure, proteostasis, UK Biobank, mass spectrometry