Beyond proteostasis: LONP1 as an immunometabolic checkpoint in health and disease

Mitochondrial Lon protease 1 (LONP1) is an ATP-dependent protease involved in mitochondrial protein quality control, mitochondrial DNA (mtDNA) maintenance, and stress adaptation. Beyond this canonical role, accumulating evidence links LONP1 to metabolic rewiring, inflammatory signaling, immune-cell polarization, and disease-associated mitochondrial dysfunction. Recent human LONP1 cryo-electron microscopy (cryo-EM) structures have revealed nucleotide- and substrate-dependent conformational states, including fold-sensing intermediates, pore-loop rearrangements, and catalytic-site organization, providing a structural framework for substrate processing and state-dependent ligandability. Functionally, LONP1 regulates the turnover or stability of metabolic enzymes such as pyruvate dehydrogenase kinase 4 (PDK4), 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), and aconitase 2 (ACO2), thereby influencing carbon flux, epigenetic regulation, and immune-related metabolic programs. LONP1 deficiency or dysfunction can promote mitochondrial stress responses, including mtDNA release and cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING)-dependent inflammation, with implications for aging, pulmonary fibrosis, developmental disorders such as cerebral, ocular, dental, auricular, and skeletal anomalies (CODAS) syndrome, and organ injury. Conversely, increased LONP1 activity or expression has been associated with tumor progression, desmoplastic remodeling, ferroptosis resistance, and viral pathogenesis in selected models, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coxsackievirus B3 (CVB3). Pharmacological studies, including activators, dual-target inhibitors, and bortezomib-bound structural complexes, support the potential ligandability of LONP1 but also highlight unresolved issues in selectivity, target engagement, mitochondrial toxicity, and context-dependent therapeutic windows. This review summarizes current structural, mechanistic, and pharmacological evidence for LONP1 as a context-dependent immunometabolic regulatory node and discusses limitations and open questions that must be addressed before clinical translation.