Upregulated TRPM1 is associated with apoptosis in Rs1 knockout mice and in ARPE19 cells through increased intracellular calcium

The pathological mechanism underlying retinal apoptosis in X-linked retinoschisis (XLRS), a disease caused by retinoschisin 1 (RS1) deficiency, remains incompletely understood. This study aimed to investigate the role of transient receptor potential melastatin 1 (TRPM1) in retinal tissues and cells. Retinal function and structure were assessed by electroretinography (ERG) and optical coherence tomography (OCT). Protein expression was evaluated by immunofluorescence staining and western blotting (WB). Retinal morphology was examined by hematoxylin and eosin (H&E) staining. Apoptotic retinal cells were detected by TUNEL staining. Key proteins were screened using proteomics data obtained by mass spectrometry. Intracellular calcium levels were measured using Rhod-2 AM. TRPM1 expression in Rs1-KO mice was 1.3-fold higher than that in wild-type mice (p < 0.05), whereas TRPM1-overexpressing ARPE19 cells exhibited approximately twofold higher expression than the empty vector control group. Mechanistically, TRPM1-mediated calcium influx promoted calcium/calmodulin-dependent protein kinase II (CAMKII) phosphorylation. Concomitantly, the accumulation of the autophagy-related proteins P62 and LC3B, increased BAX expression, and decreased BCL2 expression were observed in both Rs1-KO retinal tissues and TRPM1-overexpressing ARPE19 cells. These findings collectively suggest that TRPM1 may contribute to cell's apoptosis. Our study provides new insight into the mechanism of retinal apoptosis in XLRS.