A SP1-Driven Translational-Proteostatic Checkpoint Modulates the Autophagy-Proteasome Network

Abstract Cellular homeostasis depends on the tightly coordinated transcription, translation, and proteostasis networks. How prolonged stress decouples these multi-dimensional networks to drive degenerative cell state drift remains unclear. Using chondrocytes, which endure long-term mechanical stress, as a model, we integrated human single-cell omics, spatial imaging, population genetics, and in vivo functional validation to map the spatiotemporal evolution of cell state instability. We identified SP1 as a key regulator maintaining network integrity, repressing eEF2K transcriptionally and binding it in the cytoplasm to enforce a dual-inhibition safety lock within a “translational-proteostatic checkpoint”. Prolonged stress disrupts the checkpoint, hyper phosphorylates eEF2, blocks translation elongation and depletes short-lived autophagy-proteasome and organelle effectors leading to autophagic flux failure, mitochondrial-lysosomal uncoupling, and organelle collapse. This dysfunction in clearance, rather than increased synthesis, drives abnormal SPP1 secretion, reprogramming the secretome and promote inflammatory chondrocyte phenotype. Mendelian randomization links this module and osteoarthritis risk, while targeted genetic and pharmacological interventions successfully restore proteostasis and reverse degenerative phenotypes in situ without requiring exogenous stem cells. Ultimately, by defining this translational-proteostatic checkpoint, our study elucidates a fundamental paradigm of how cells safeguard their state identity against chronic stress, providing a broad, stem-cell-independent conceptual and therapeutic framework to counteract cellular degeneration across diverse tissue.