Stress granules at the crossroads of the proteostasis network.

The proteostasis network maintains cell function by safeguarding the proteome through the coordinated actions of protein synthesis, quality control, and degradation machinery including chaperones and the ubiquitin-proteasome system. Proteostasis collapse and activation of the integrated stress response (ISR) occur in ageing and neurodegeneration. Upon proteotoxic stress, translation suppression during the ISR drives the assembly of non-translating mRNAs into biomolecular condensates called stress granules. Stress granules act as a double-edged sword in the proteostasis network, serving beneficial or detrimental roles through their effects on translation, protein quality control, and protein aggregation. In this review, we discuss how protein synthesis, quality control, and degradation factors regulate stress granule dynamics, and conversely how stress granules impact proteostasis. While stress granules may initially protect cells by sequestering misfolded, aggregation-prone proteins and regulating translation, they may evolve into sites of pathological aggregation. Clarifying these intersections may reveal therapeutic strategies for neurodegeneration and other disease processes.