bims-mideyd 2026-09-06 papers

Cell Biochem Funct. 2026 Sep;44(9): e70294

Syntaxin-3 Regulates Tight Junction Assembly in Human Retinal Pigment Epithelium.

Athira Ramesh, Suganya Sivagurunathan, Navya Valavath Baburajan, Subbulakshmi Chidambaram.

The retinal pigment epithelium (RPE) consists of polarized epithelial cells, serving as a support system for photoreceptor maintenance, where the polarity is contributed by the distribution of syntaxins (STX) within the cell. STX3, a known regulator of apical trafficking in epithelial cells, was previously understood to be absent in human RPE cells, with its functions thought to be compensated by STX1A. However, our results on SNARE mRNA expression profile in RPE detected the presence of 2 splice variants of STX3. Further investigation in donor retina, primary hRPE, and ARPE-19 cells revealed detectable levels of STX3 mRNA and protein. STX3 knockdown in ARPE19 resulted in a significant reduction of tight junction (TJ) proteins, compromising TJ assembly, highlighting the critical role of STX3 in maintaining RPE integrity. In addition, immunoprecipitation followed by LC-MS/MS analysis revealed that STX3 and STX1A have a distinct novel protein interactome in RPE. This study identified unique and shared interactants for STX3 and STX1A, suggesting a broader role for RPE beyond its traditional photoreceptor support function. This further emphasizes the biological significance of STX1A and STX3 in maintaining retinal homeostasis, which could facilitate the development of novel therapeutic strategies for retinal disorders.

Keywords: plasticity; polarity; retinal pigment epithelium; syntaxin1A; syntaxin3; tight Junctions

DOI: https://doi.org/10.1002/cbf.70294

Exp Eye Res. 2026 Sep 01. pii: S0014-4835(26)00381-7. [Epub ahead of print]272 111225

Polarized secretion of mitochondrial DNA by retinal pigment epithelial cells.

David Sekáč, Georgina Faura, Marte Eikenes, Natasha Josifovska, Goran Petrovski, Zdenka Ellederová, Lars Eide.

Mitochondrial DNA (mtDNA) damage is strongly implicated in age-related macular degeneration (AMD), the most frequent cause of age-mediated visual impairment in developed countries. Here, we investigated and compared the fate of acutely induced oxidation damage in primary retinal pigment epithelial (RPE) cells. The individual RPE clones responded heterogeneously to hydrogen peroxide, both with respect to cell sensitivity and mtDNA damage formation. Peroxide-induced mtDNA damage in human RPE (hRPE) was fully repaired within 4 h. In parallel, hRPE cells secreted mtDNA from both apical and basolateral surfaces (AP-mtDNA and BL-mtDNA, respectively) independent of peroxide exposure and that could not be explained by detached cells. Most mtDNA was released apically, and the quality of AP-mtDNA was comparable to that of intracellular mtDNA (c-mtDNA). In contrast, BL-mtDNA constituted only 3% of AP-mtDNA, and exhibited a 10-fold higher damage burden. The difference in mtDNA quality suggests a non-random selection of mtDNA molecules to be targeted for export in apical versus basolateral direction. To investigate this, we analyzed epigenetic marks (m.545 methylation) and SNPs (heteroplasmies) in extracellular and cellular mtDNA. Extracellular mtDNA in general appeared to be more modified than c-mtDNA and that AP-mtDNA differs from BL-mtDNA, which is indicative of a targeted secretion. Porcine RPEs (pRPEs) from a minipig model of Huntington's Disease associated with impaired epithelial polarity (TgHD) displayed approximately 2-fold higher leakage of AP-mtDNA than control pRPEs, but lower than hRPEs. Together, our data imply that extracellular mtDNA originating from RPE shapes the outer retina and the implications for polar secretion are discussed.

Keywords: DNA damage; Extracellular mtDNA; Huntington's disease; Polarized secretion; RPE; mtDNA

DOI: https://doi.org/10.1016/j.exer.2026.111225

ACS Appl Bio Mater. 2026 Aug 26.

Low-Frequency Ultrasound Mechanostimulation for Targeting Fibrotic Cells for Proliferative Vitreoretinopathy Treatment.

Nandhini Krishnamurthy, Nishka Kaushal, Anirudh Sreenivas Bk, Gomathi Sankar, Akshay Kumar, P Mahesh Shanmugham, Sriram Simakurthy, Trichur Raju, Rishikesh Balvalli, Rudra Pratap, Sangeeta Nath, Ajay Tijore.

Proliferative vitreoretinopathy (PVR) is a retinal disorder characterized by migration of retinal pigment epithelial cells (RPE) into the vitreous cavity through the retinal tear and their epithelial-to-mesenchymal transition (EMT), followed by the development of a fibrotic condition. Here, we demonstrate that low-frequency ultrasound (LFU) applied using a controlled ultrasonic actuation platform selectively induces apoptosis in EMT-activated RPE cells through LFU-mediated mechanical forces, without damaging normal RPE cells. Furthermore, LFU treatment disrupts myosin IIA-mediated contractility and decreases the 2D migration of activated RPE cells. MicroRNA-21 (miR-21) secreted by activated RPE cells reduces the expression of the mechanosensory cytoskeletal protein tropomyosin 2.1 (Tpm2.1) in these cells, rendering them susceptible to mechanoptosis. Surprisingly, normal RPE cells that retain Tpm2.1 expression remain unaffected under identical conditions. These findings suggest that cell-state-dependent mechanical vulnerability of RPE cells signifies a therapeutic opportunity and could establish LFU as a noninvasive treatment to selectively kill fibrotic RPE cells, with potential applications in retinal and fibrotic disorders.

Keywords: low-frequency ultrasound (LFU); miR-21; proliferative vitreoretinopathy (PVR); retinal pigment epithelial cells; tropomyosin 2.1

DOI: https://doi.org/10.1021/acsabm.6c01243

PLoS One. 2026 ;21(9): e0355473

EIF1 coordinates transcriptomic and splicing networks associated with cell cycle dysregulation in diabetic retinopathy.

Na Li, Qian Ma, Xin Fan, Qi Liu, Li Liu, Shengfu Zhang, Yaling Ma, Hongxia Xu, Xinyi Li.

PURPOSE: EIF1, an RNA-binding protein implicated in multiple diseases, remains poorly characterized in diabetic retinopathy (DR). This study therefore investigated EIF1 expression and function in an in vitro model of DR pathogenesis.
METHODS: Human retinal pigment epithelial cells (ARPE-19) were exposed to 50 mM glucose to model DR. EIF1 was knocked down using siRNA under hyperglycemic conditions, followed by transcriptome sequencing (RNA-seq) to profile differentially expressed genes (DEGs) and alternative splicing events (ASEs). Key findings from RNA-seq were validated by RT-qPCR.
RESULTS: High-glucose treatment significantly suppressed cellular proliferation concurrent with EIF1 downregulation, suggesting that hyperglycemia-induced EIF1 depletion may impair retinal pigment epithelial cell functionality. Transcriptome sequencing revealed that EIF1 knockdown induced differential expression in 223 genes in total, comprising 35 upregulated and 188 downregulated genes. Notably, functional enrichment analysis revealed that downregulated genes are significantly enriched in cell cycle-related signaling pathways. Additionally, 1211 differential alternative splicing events were detected, primarily impacting cell cycle and p53 signaling pathways. Further analysis uncovered differentially expressed genes (e.g., BIRC5, MCM4, PLK1, RAD51, MELK, UBE2C, GINS2, and FANCA) and differentially spliced genes (e.g., COP1, TFE3) associated with the cell cycle after EIF1 knockdown. RT-qPCR validation confirmed the differential expression of key DEGs and the altered splicing patterns of COP1 and TFE3, consistent with RNA-seq predictions. These findings suggest that EIF1 may be associated with cell cycle dysregulation through the modulation of both gene expression and alternative splicing.
CONCLUSIONS: This study suggests a potential role for EIF1 in DR pathogenesis in an in vitro model, identifying it as a candidate for further investigation. The data point to an association between EIF1 and the regulation of cell cycle-related genes at both the transcriptional and splicing levels.

DOI: https://doi.org/10.1371/journal.pone.0355473

Biochemistry (Mosc). 2026 Aug;91(8): 1417-1431

Marina A Yakovleva, Alexey A Kostyukov, Natalya L Aronshtam, Patimat M Shilkrot, Sergei A Borzenok, Vladimir A Kuzmin, Tatiana B Feldman, Aleksandr E Dontsov, Mikhail A Ostrovsky.

Lipofuscin granules (LGs) in retinal pigment epithelium (RPE) cells contain bis-retinoids and their oxidation and degradation products, rendering them photo- and cytotoxic to intracellular structures. LGs are implicated in the pathogenesis of multiple visual pathologies, including age-related macular degeneration (AMD). They exhibit strong autofluorescence, which has led to the development of fundus autofluorescence (FAF) imaging as a non-invasive diagnostic method in ophthalmology. Spectral analysis of autofluorescence can expand the capabilities of this method, including for preclinical diagnostics, as pathological conditions are often associated with increased proportions of oxidized bis-retinoid derivatives that alter LG autofluorescence parameters. However, limited knowledge of age-dependent changes in LG bis-retinoid composition remains a key limitation. In this study, we combined fluorescence spectroscopy, confocal fluorescence microscopy, and fluorescence lifetime imaging (time-correlated single-photon counting) to demonstrate that, under physiological conditions, aging is accompanied by a progressive increase in the relative abundance of oxidation and degradation products of bis-retinoids in LGs. These findings provide an age-dependent baseline for distinguishing physiological and pathological states, thereby improving the potential of FAF imaging for early (preclinical) diagnosis.

Keywords: autofluorescence; bis-retinoids; eye; lipofuscin granules; retinal pigment epithelium

DOI: https://doi.org/10.1134/S0006297926600985