Phenylalanyl-tRNA Synthetase Regulates Aging through Modulation of Intracellular dsRNA

Cellular senescence is a fundamental cause of aging and aging-related diseases. When double-stranded RNA (dsRNA) is properly recognized, it supports cellular homeostasis; however, its excessive activation triggers inflammatory pathways and has been implicated in the development of multiple degenerative diseases. Recent evidence suggests that the accumulation of dsRNA and activation of sensor protein kinase R (PKR) are major causes of the inflammatory response in senescent cells. Surprisingly, this PKR activation by intracellular endogenous dsRNA also occurs in uninfected cells and has been reported to play a role in diseases accompanied by abnormal immune activation. We find that manipulation of dsRNA processing mechanisms could modulate aging. Specifically, FARSA (the alpha subunit of phenylalanyl-tRNA synthase) was investigated as a potential regulator of dsRNA-mediated aging. The aim of this study was to determine whether FARSA affects the progression of cellular aging through the process of regulating intracellular dsRNA levels and immune signals.

In addition to dsRNA generated during virus infection, mitochondria are a critical source of double-stranded RNA (mt-dsRNA), which arises from bidirectional transcription of the mitochondrial genome. Accumulation of mt-dsRNA can lead to activation of PKR and initiation of inflammatory signaling. Inducible tetracycline-shRNA system (TET-shFARSA) was used to knockdown FARSA in human cell culture and we monitored its knockdown efficiency over time. After FARSA silencing, we investigated mt-dsRNA regulatory pathways by evaluating mt-dsRNA accumulation and quantifying key dsRNA regulatory genes (PNPT1, SUV3, POLRMT). Our findings showed that FARSA knockdown led to the accumulation of senescence markers. Furthermore, we linked FARSA loss to inflammatory signals through evaluation of PKR activation status (phosphorylated PKR and its substrate eIF2α). We found that co-knockdown of FARSA and PKR attenuated the senescence phenotype. To test the functional significance of the dsRNA binding ability of FARSA, we performed rescue experiments by overexpressing wild-type FARSA and dsRNA binding defect mutation (K428A) in FARSA-deficient cells. This approach allowed us to observe whether the mutation could rescue the senescence phenotypes.

These findings can open up new possibilities for targeting FARSA in age-related disease models. Ongoing in vivo studies using C.elegans and mouse models will further explore the therapeutic potential of FARSA regulation in lifespan regulation and inflammatory aging.