Glycine Aminoacyl-tRNA Synthetase Promotes Renal Tubulointerstitial Fibrosis in Diabetic Nephropathy by Facilitating Collagen Translation

Background: Tubulointerstitial abnormalities are strong predictors of diabetic nephropathy (DN) progression and represent promising therapeutic targets. Tubulointerstitial fibrosis, a hallmark of DN, is characterized by myofibroblast accumulation and excessive deposition of extracellular matrix components, particularly collagen. Aberrant collagen deposition not only marks fibrosis but also actively contributes to renal functional decline. Therefore, reducing collagen synthesis is critical for mitigating renal fibrosis. Methods: The expression of glycine aminoacyl-tRNA synthetase (GARS) in renal tubular epithelial cells was analyzed in kidney biopsy samples from DN patients. A tubule-specific Gars knockout mouse model was established, and GARS expression was silenced in vitro using siRNA in HK-2 cells. Pharmacological inhibition of GARS was employed both in vitro and in vivo. Collagen synthesis efficiency was evaluated through tRNA sequencing and polysome profiling to investigate the role of GARS in DN pathogenesis. Results: Single-cell RNA sequencing and kidney biopsy analyses revealed upregulated GARS expression in tubular epithelial cells from DN patients. Similarly, STZ-induced diabetic mice exhibited increased renal GARS levels. Tubule-specific deletion of Gars alleviated renal injury and attenuated fibrosis. In HK-2 cells, high glucose stimulation led to elevated GARS expression. Pharmacological inhibition of GARS reduced the translation—but not the transcription—of multiple collagen proteins, thereby decreasing expression of fibrosis-related markers. GARS knockdown under high-glucose conditions produced similar antifibrotic effects. Co-immunoprecipitation and mass spectrometry identified an interaction between GARS and RRBP1, a protein essential for endoplasmic reticulum (ER)-associated translation. GARS silencing or inhibition diminished RRBP1 expression and its ER localization, suggesting reduced translational capacity. Furthermore, RRBP1 overexpression enhanced fibrotic marker expression and exacerbated tubular injury. Conclusion: These findings identify GARS as a key regulator of collagen translation and a driver of renal tubulointerstitial fibrosis in diabetic nephropathy. Targeting the GARS–RRBP1 axis may represent a promising therapeutic strategy to reduce renal collagen deposition and slow disease progression.