HR3/RORα-mediated cholesterol sensing regulates TOR signaling

Summary Cells and organisms adjust their growth based on the availability of cholesterol, which is essential for cellular functions. However, the mechanisms by which cells sense cholesterol levels and translate these into growth signals are not fully understood. We report that cholesterol rapidly activates the master growth-regulatory TOR pathway in Drosophila tissues. We identify the nuclear receptor HR3, an ortholog of mammalian RORα, as an essential factor in cholesterol-induced TOR activation. We demonstrate that HR3 binds cholesterol and promotes TOR pathway activation through a non-genomic mechanism acting upstream of the Rag GTPases. Similarly, we find that RORα is necessary for cholesterol-mediated TOR activation in human cells, suggesting that HR3/RORα represents a conserved mechanism for cholesterol sensing that couples cholesterol availability to TOR-pathway activity. These findings advance our understanding of how cholesterol influences cell growth, with implications for cholesterol-related diseases and cancer. Highlights Cholesterol leads to dynamic TOR pathway activation, driving systemic growth HR3 in Drosophila binds cholesterol and couples its availability to TOR activation HR3 acts upstream of Rag GTPases to activate TOR in response to lysosomal cholesterol Mammalian HR3 ortholog RORα is required for cholesterol-induced TOR activation