Objectives: Podocyte injury is a prediction marker of diabetic nephropathy (DN), and AKT/mTOR pathway-mediated inhibition of autophagy is widely reported to contribute to podocyte damage. Recent study stated that sperm-associated antigen 5 (SPAG5) activated AKT/mTOR signalling in bladder urothelial carcinoma, indicating SPAG5 might regulate autophagy and play a role in podocyte damage.
Materials and methods: Apoptosis and autophagy of human podocytes (HPCs) were detected by flow cytometry and immunofluorescence (IF). Gene level was assessed by Western blot and RT-qPCR. Molecular interactions were determined by pulldown, RNA immunoprecipitation (RIP), co-immunoprecipitation (co-IP), chromatin immunoprecipitation (ChIP) and luciferase reporter assays.
Results: SPAG5 mRNA and protein levels were upregulated under high glucose treatment in HPCs. Silencing SPAG5 reversed the increase of apoptosis and decrease of autophagy in high glucose-treated HPCs. Later, we found a long non-coding RNA (lncRNA) SPAG5 antisense RNA1 (SPAG5-AS1) as a neighbour gene to SPAG5. Mechanistically, YY1 transcriptionally upregulated SPAG5-AS1 and SPAG5 in high glucose-treated podocytes. SPAG5-AS1 acted as a competitive endogenous RNA (ceRNA) to regulate miR-769-5p/YY1 axis and induce SPAG5. SPAG5-AS1 interacted with ubiquitin-specific peptidase 14 (USP14) and leads to de-ubiquitination and stabilization of SPAG5 protein.
Conclusions: This study revealed that SPAG5-AS1 inhibited autophagy and aggravated apoptosis of podocytes via SPAG5/AKT/mTOR pathway, indicating SPAG5-AS1/SPAG5 as a potential target for the alleviation of podocyte injury and offering new thoughts for the treatments of DN.
Keywords: AKT/mTOR; SPAG5; SPAG5-AS1; autophagy; diabetic nephropathy; podocyte injury.
© 2020 The Authors. Cell Proliferation Published by John Wiley & Sons Ltd.