Angiogenin-Cleaved tRNA Halves Interact with Cytochrome <i>c</i>, Protecting Cells from Apoptosis during Osmotic Stress

Abstract

Adaptation to changes in extracellular tonicity is essential for cell survival. However, severe or chronic hyperosmotic stress induces apoptosis, which involves cytochrome c (Cyt c) release from mitochondria and subsequent apoptosome formation. Here, we show that angiogenin-induced accumulation of tRNA halves (or tiRNAs) is accompanied by increased survival in hyperosmotically stressed mouse embryonic fibroblasts. Treatment of cells with angiogenin inhibits stress-induced formation of the apoptosome and increases the interaction of small RNAs with released Cyt c in a ribonucleoprotein (Cyt c-RNP) complex. Next-generation sequencing of RNA isolated from the Cyt c-RNP complex reveals that 20 tiRNAs are highly enriched in the Cyt c-RNP complex. Preferred components of this complex are 5' and 3' tiRNAs of specific isodecoders within a family of isoacceptors. We also demonstrate that Cyt c binds tiRNAs in vitro, and the pool of Cyt c-interacting RNAs binds tighter than individual tiRNAs. Finally, we show that angiogenin treatment of primary cortical neurons exposed to hyperosmotic stress also decreases apoptosis. Our findings reveal a connection between angiogenin-generated tiRNAs and cell survival in response to hyperosmotic stress and suggest a novel cellular complex involving Cyt c and tiRNAs that inhibits apoptosome formation and activity.