Tubular FHL2 Promotes Cellular Senescence Through Inhibiting CCR4-NOT Deadenylase Complex Activity and Wnt16 mRNA Decay

Background: Cellular senescence of renal tubular epithelial cells (TECs) contributes to renal aging. Four-and-a-half LIM domains protein 2 (FHL2) is one of the top predictive genes of aging. However, the potential role and mechanism of FHL2 in renal aging remains to be clarified. Methods: Mice with proximal TECs-specific deletion of FHL2 were generated by mating FHL2-floxed mice with Ggt1-Cre transgenic mice. Two mouse models of renal aging were used: D-galactose (D-gal)-induced accelerated aging and streptozotocin-induced diabetic kidney disease (DKD). In cultured primary TECs from mice, cellular senescence was induced by D-gal or high glucose (HG). Results: FHL2 mRNA and protein expression were induced in a time-dependent pattern during renal aging both in vivo and in vitro. Deficiency of FHL2 in proximal TECs restrained renal aging in mouse models. Knockdown of FHL2 expression suppressed cellular senescence induced by D-gal or HG in vitro. Immunoprecipitation mass spectrometry analysis revealed that the protein molecules most bound to FHL2 were CNOT1 and TAB182, which are known as components of CCR4-NOT deadenuosylase complex. Overexpression of FHL2 induced an increase in physical interaction between FHL2 and CNOT1 or TAB182, which led to their ubiquitination and proteasomal degradation, resulting in a decrease in CCR4-NOT complex activity. Either overexpression of FHL2 or treatment with D-gal or HG could increase total mRNA containing adenine N6 site methylation (m6A) mortification, which is consistent with the known report that CCR4-NOT complex regulates RNA degradation depending on the RNA modified by m6A. Methylated RNA immunoprecipitation sequencing analysis revealed that upregulation of FHL2 attenuated the decay of Wnt16 mRNA modified by m6A, then increased Wnt16 mRNA and protein expression. Activation of β-catenin and mTORC1 pathways and cellular senescence evoked by overexpression of FHL2 were suppressed by knockdown of Wnt16 expression. Conclusion: These results suggest that FHL2, through inhibiting CCR4-NOT complex activity and Wnt16 mRNA decay, plays a crucial role in mediating cellular senescence in TECs, and could be a potential therapeutic target for impeding renal aging. Funding: Government Support – Non-U.S.