SMDT1 (single-pass membrane protein with aspartate rich tail 1) encodes an essential regulatory subunit of the mitochondrial calcium uniporter (MCU) complex that mediates calcium uptake into mitochondria 123. SMDT1 functions as a critical bridge between the calcium-sensing protein MICU1 and the calcium-conducting subunit MCU, enabling activation of MCU while retaining MICU1 at the pore to ensure tight regulation of the complex and appropriate cellular responses to calcium signaling 134. Dysfunction of SMDT1 impairs mitochondrial calcium uptake with significant disease relevance. Pathogenic SMDT1 variants cause loss of EMRE protein (encoded by SMDT1), impair mitochondrial calcium uptake, and manifest as muscle-related symptoms 5. Abnormal mitochondrial calcium handling—a hallmark of conditions like diabetic cardiomyopathy—represents a therapeutic target 6. In pancreatic ductal adenocarcinoma, SMDT1 overexpression suppresses proliferation and induces apoptosis through mitochondrial fragmentation and cytochrome c release 7. Mendelian randomization analysis identified SMDT1 expression as causally associated with sudden cardiac death and cardiovascular diseases including myocardial infarction and cardiomyopathy 8. Additionally, SMDT1 participates in angiotensin II-induced mitochondrial injury in vascular smooth muscle cells relevant to abdominal aortic aneurysm pathology 9, and its expression correlates with lung cancer risk 10.