LECT2-RPS27A interaction involving Lys48 attenuates neuroinflammation in diabetic retinopathy

Leukocyte cell-derived chemotaxin 2 (LECT2), a newly discovered hepatokine involved in immunomodulation and inflammatory processes, has recently been implicated in diabetic retinopathy pathogenesis. However, the specific role and mechanism of LECT2 in diabetic retinopathy remain largely unclear.

A publicly available liquid biopsy proteomics dataset was reanalysed and validated using retinal samples from individuals with diabetic retinopathy. A LECT2-knockdown (Lect2^+/-) mouse model of diabetic retinopathy was established to evaluate the role of LECT2 in vivo. Retinal pathology was assessed by Periodic Acid-Schiff staining and H&E staining, and LECT2 expression was assessed by western blotting. In parallel, a high glucose (HG)-induced human Müller cell model was used to investigate the subcellular localisation and functional effects of LECT2. LECT2 expression and inflammatory signalling were analysed following LECT2 knockdown or overexpression, and its nucleus-cytoplasm distribution was examined by fractionation assays. The interaction between LECT2 and ribosomal protein S27a (RPS27A) was characterised by immunoprecipitation-MS, co-immunoprecipitation, molecular docking and split-GFP assays, followed by RPS27A silencing to assess its effects on inflammatory protein expression.

Proteomic reanalysis of proliferative diabetic retinopathy liquid biopsy data identified 1479 upregulated proteins, with chemotaxis among the most significantly enriched Gene Ontology terms (false discovery rate <0.001). Among 17 chemotaxis-related candidate proteins, LECT2 emerged as a potential regulator of diabetes-associated inflammation, a finding further supported by its elevated expression in the retinas of individuals with diabetic retinopathy. In diabetic Lect2^+/- mice, LECT2 deficiency aggravated retinal microvascular injury and inflammatory responses. LECT2 was predominantly expressed in retinal Müller cells, implicating it in glia-associated retinal inflammation. In HG-treated human retinal Müller cells, RPS27A was identified as a downstream target of LECT2 and was upregulated under hyperglycaemic conditions. Mechanistically, HG stimulation increased the expression and nuclear accumulation of both LECT2 and RPS27A. LECT2 interacted with RPS27A at the Lys48 site, promoting its nuclear retention and limiting its cytoplasmic translocation. This, in turn, inhibited IκBα ubiquitination and degradation, thereby suppressing NF-κB-driven inflammatory signalling.

Taken together, our studies indicated the protective role of LECT2 in diabetes-induced dysfunction of retinal Müller cells, supporting the feasibility of targeting LECT2 in the management of diabetic inflammation and microvasculopathy.