GRP75-dependent SIMPA mediates inter-organellar quality control.

GRP75-dependent SIMPA formation at mitochondria-ER contact sites mediates inter-organellar communication to maintain mitochondrial integrity under proteostatic stress.

• Why it matters: Understanding how cells coordinate mitochondrial quality control and stress signaling across organelles is crucial for insights into cellular health and disease mechanisms.
• What they did: The study used quantitative proteomics and microscopy to show that damaged mitochondrial proteins form SIMPA aggregates that interact with ER contact sites, with GRP75 regulating their biogenesis and signaling pathways.
• The result: A GRP75-dependent SIMPA signaling cascade reduces mitochondrial stress and preserves mitochondrial function in cellular and liver disease models, highlighting SIMPA's role as a central hub for mitochondrial quality control.