RSL1D1 modulates cell senescence and proliferation via regulation of PPARγ mRNA stability

In this study, we will examine if RSL1D1 influences PPARγ expression and explore the underlying mechanism that RSL1D1 regulates PPARγ expression. Moreover, the significance of RSL1D1-PPARγ pathway in cell senescence and proliferation will also be determined.

Our main methods include western blotting, immunoprecipitation (IP), real-time PCR, RNA Immunoprecipitation (RIP), biotin-labeled RNA pull down assay, dual luciferase reporter gene assay, senescence-associated β-galactosidase staining, cell proliferation assay, colony formation assay, wound healing assay, blood biochemistry test and Oil red O staining.

By analyzing gene chip results we find that the expression of RSL1D1 and PPARγ might be correlated. Then we show that RSL1D1 is a posttranscriptional regulator of PPARγ. RSL1D1 overexpression elevates, while RSL1D1 knockdown inhibits, PPARγ mRNA and protein expression levels. Mechanistically, we find that RSL1D1 directly interacts with the 3'-untranslated region of PPARγ mRNA, and then promotes its stability and increases PPARγ protein expression level. We further demonstrate that RSL1D1 modulates cellular senescence and cell proliferation partially via PPARγ-regulated downstream target genes such as PTEN/p27, NF-κB, GLUT4, and ACL. Moreover, we find that RSL1D1 regulates PPARγ expression and function in a HuR-dependent manner. Last, we show that RSL1D1 knockout in mouse adipose tissue shortens mouse lifespan and leads to hepatic damage which may impair liver damage repair function.

Collectively, our findings unveil a novel posttranscriptional regulation of PPARγ by RSL1D1 and uncover a critical role of RSL1D1-PPARγ-PPARγ downstream target genes in regulating cellular senescence and cell proliferation.