Nuclear translocation ability of Lipin differentially affects gene expression and survival in fed and fasting .

Lipins are eukaryotic proteins with functions in lipid synthesis and the homeostatic control of energy balance. They execute these functions by acting as phosphatidate phosphatase enzymes in the cytoplasm and by changing gene expression after translocation into the cell nucleus, in particular under fasting conditions. Here, we asked whether nuclear translocation and the enzymatic activity of Lipin serve essential functions and how gene expression changes, under both fed and fasting conditions, when nuclear translocation is impaired. To address these questions, we created a null mutant, a mutant expressing Lipin lacking a nuclear localization signal ( ), and a mutant expressing enzymatically dead Lipin. Our data support the conclusion that the enzymatic but not nuclear gene regulatory activity of Lipin is essential for survival. Notably, adult flies were not only viable but also exhibited improved life expectancy. In contrast, they were highly susceptible to starvation. Both the improved life expectancy in the fed state and the decreased survival in the fasting state correlated with changes in metabolic gene expression. Moreover, increased life expectancy of fed flies was associated with a decreased metabolic rate. Interestingly, in addition to metabolic genes, genes involved in feeding behavior and the immune response were misregulated in flies. Altogether, our data suggest that the nuclear activity of Lipin influences the genomic response to nutrient availability with effects on life expectancy and starvation resistance. Thus, nutritional or therapeutic approaches that aim at lowering nuclear translocation of lipins in humans may be worth exploring.