AMC-F1 regulates mitochondria-autophagy crosstalk independent of nutrient stress.

Mitochondria and autophagy are fundamental yet distinct regulators of cellular homeostasis. Here, we identify AMC-F1 (Autophagy-Mitochondria Coupling Factor 1; formerly TRIM44) as a central integrator of mitochondrial bioenergetics and autophagy. Using Amcf1 knockout and knock-in mouse models, we demonstrate that AMC-F1 bidirectionally regulates these pathways: its loss reduces mitochondrial respiration and autophagic flux, whereas its overexpression promotes mitochondrial elongation and increases autophagy independently of nutrient stress. Transcriptomic analyses reveal AMC-F1-dependent regulation of mitochondrial biogenesis programs that engage autophagy, involving mitochondrial respiratory chain complex genes under basal conditions and mitochondrial organization factors under starvation-induced autophagy. Although dispensable under homeostasis, this coupling becomes essential during stress adaptation. In an acute liver-injury model, Amcf1 knock-in mice were fully protected, exhibiting elevated OPA1, reduced caspase-3 and PARP activation, and preserved Beclin 1. This functional duality reflects AMC-F1's ability to modulate the mitochondrial integrated stress response (mtISR), enabling adaptive ATF4 signaling while preventing maladaptive responses when stress exceeds a threshold. Autophagy upregulation by AMC-F1 is critical for fine-tuning the ISR and preserving cellular resilience. Together, our findings position AMC-F1 as a stress-responsive gatekeeper and a novel coordinator of mitochondrial-autophagy crosstalk, defining a cellular state primed for stress adaptation.