Tissue-specific roles of GCN2 in aging and autosomal dominant retinitis pigmentosa.

The organisms have the capacity to sense and adapt to their surroundings for their life in a dynamic environment. In response to amino acid starvation, cells activate a rectifying physiological program, termed the integrated stress response (ISR), to restore cellular homeostasis. General controlled non-repressed (GCN2) kinase is a master regulator of the ISR and modulates protein synthesis in response to amino acid starvation. We previously established the GCN2/ATF4/4E-BP pathway in development and aging. Here, we investigated the tissue-specific roles of GCN2 upon dietary restriction of amino acid in a Drosophila model. The knockdown of GCN2 in the gut and fat body, an energy sensing organ in Drosophila, abolished the beneficial effect of GCN2 in lifespan extension upon dietary restriction of amino acids. Proteome analysis in an autosomal dominant retinitis pigmentosa (ADRP) model showed that dietary restriction of amino acids regulates the synthesis of proteins in several pathways, including mitochondrial translation, mitochondrial gene expression, and regulation of biological quality, and that gcn2-mutant flies have reduced levels of these mitochondria-associated proteins, which may contribute to retinal degeneration in ADRP. These results indicate that the tissue-specific regulation of GCN2 contributes to normal physiology and ADRP progression.