TMEM223 is a mitochondrial ribosome-associated protein that functions as a critical assembly factor for cytochrome c oxidase complex (complex IV) biogenesis 1. It stimulates translation of MT-CO1 mRNA and serves as a constituent of early COX1 assembly intermediates, linking early assembly stages to the mitochondrial translation machinery 1. TMEM223 belongs to the TMEM70/TMEM186/TMEM223 protein family, which is evolutionarily conserved exclusively in species possessing OXPHOS complexes, suggesting fundamental importance for oxidative phosphorylation 2. Beyond its mitochondrial role, TMEM223 functions as a voltage-gated Ca²⁺ channel interaction partner, lowering average current density and modulating calcium channel inactivation kinetics, potentially negatively regulating Ca²⁺ entry required for neurotransmitter release 3. Clinical relevance includes associations with cancer prognosis; lower TMEM223 expression correlates with better progression-free survival and macrophage infiltration patterns in breast cancer 4. Additionally, TMEM223 has been identified as part of a genetically regulated protein module associated with cognitive resilience in Alzheimer's disease mouse models, suggesting potential involvement in neuroprotection 5. These diverse functions reflect TMEM223's roles in both mitochondrial bioenergetics and neuronal calcium signaling.