TIMM9 (translocase of inner mitochondrial membrane 9) is a mitochondrial intermembrane chaperone that facilitates the import and insertion of multi-pass transmembrane proteins into the mitochondrial inner membrane. It protects hydrophobic protein precursors from aggregation while guiding them through the intermembrane space, functioning as a component of the TIM translocase complex. Mechanistically, TIMM9 acts as a chaperone-like protein with zinc ion binding capacity and can homodimerize to perform its protein-folding and insertion functions 1. Its expression is regulated by mitochondrial biogenesis pathways through PGC-1α/NRF1/TFAM signaling 1. Clinically, TIMM9 dysregulation is implicated in multiple pathologies. In heart failure, TIMM9 is significantly downregulated alongside other mitochondrial quality control genes, contributing to mitochondrial dysfunction in both ischemic and dilated cardiomyopathy 2. Conversely, TIMM9 overexpression serves as a negative prognostic marker in gastric cancer, associated with poor disease-free survival and independent of other prognostic factors 3. High TIMM9 expression correlates with tumorigenesis, metastasis, and cell cycle progression in pan-cancer analyses 4, and it functions as a component of prognostic signatures in hepatocellular carcinoma 5. TIMM9 is also upregulated in breast cancer epithelial cells 6, suggesting its role in cancer cell metabolic reprogramming. These findings indicate TIMM9's dual relevance as a biomarker for disease severity and potential therapeutic target.