Arul, K. | Search bioRxiv

bioRxiv2024

Estrogen receptor-related receptor (Esrra) induces ribosomal protein Rplp1-mediated adaptive hepatic translation during prolonged starvation

Protein translation is an energy-intensive ribosome-driven process that is reduced during nutrient scarcity to conserve cellular resources. During prolonged starvation, cells selectively translate specific proteins to enhance their survival (adaptive translation); however, this process is poorly understood. Accordingly, we analyzed protein translation and mRNA transcription by multiple methods in vitro and in vivo to investigate adaptive hepatic translation during starvation. While acute starvation suppressed protein translation in general, proteomic analysis showed that prolonged starvation selectively induced translation of lysosome and autolysosome proteins. Significantly, the expression of the orphan nuclear receptor, estrogen-related receptor alpha (Esrra) increased during prolonged starvation and served as a master regulator of this adaptive translation by transcriptionally stimulating 60S acidic ribosomal protein P1 (Rplp1) gene expression. Overexpression or siRNA knockdown of Esrra expression in vitro or in vivo led to parallel changes in Rplp1 gene expression, lysosome/autophagy protein translation, and autophagy. Remarkably, we have found that Esrra had dual functions by not only regulating transcription but also controling adaptive translation via the Esrra/Rplp1/lysosome/autophagy pathway during prolonged starvation.

molecular biology↗

bioRxiv2021

Estrogen-related receptor alpha and Rplp1 ribosome protein-dependent translation coordinately regulate starvation response and decrease NASH progression

BackgroundCurrently, little is known about the mechanism(s) regulating global and specific protein translation during non-alcoholic steatohepatitis (NASH). MethodsWe used puromycin-labelling, polysome profiling, ChIPseq and ChIP-qPCR, and gene manipulation in vitro and in dietary mouse models of NASH in this study. ResultsUsing unbiased label-free quantitative proteome, puromycin-labelling and polysome profiling, we observed a global decrease in protein translation during lipotoxicity in human primary hepatocytes, mouse hepatic AML12 cells, and livers from a dietary mouse model of NASH. Interestingly, proteomic analysis showed that Rplp1, which regulates ribosome and translation pathways, was one of the most downregulated proteins. Moreover, decreased Esrra expression and binding to the Rplp1 promoter, diminished Rplp1 gene expression during lipotoxicity. This, in turn, reduced global protein translation and Esrra/Rplp1-dependent translation of lysosome (Lamp2, Ctsd) and autophagy (sqstm1, Map1lc3b) proteins. Of note, Esrra did not increase its binding to these gene promoters or their gene transcription, confirming its regulation of their translation during lipotoxicity. Notably, hepatic Esrra-Rplp1-dependent translation of lysosomal and autophagy proteins also was impaired in NASH patients and liver-specific Esrra knockout mice. Remarkably, alternate day fasting induced Essra-Rplp1-dependent expression of lysosomal proteins, restored autophagy, and reduced lipotoxicity, inflammation, and fibrosis in hepatic cell culture and in vivo models of NASH. ConclusionEsrra regulation of Rplp1-mediated translation of lysosome / autolysosome proteins was downregulated during NASH. Alternate day fasting activated this novel pathway and improved NASH, suggesting that Esrra and Rplp1 may serve as therapeutic targets for NASH. Our findings also provided the first example of a nuclear hormone receptor, Esrra, to not only regulate transcription but also protein translation, via induction of Rplp1.

molecular biology↗