MAIP1 (matrix AAA peptidase interacting protein 1) is a mitochondrial protein that plays dual roles in organellar homeostasis and metabolic regulation. Functionally, MAIP1 promotes sorting and maturation of the mitochondrial calcium uniporter subunit SMDT1/EMRE by interacting with its transit peptide in the mitochondrial matrix, protecting it from degradation by YME1L1 and facilitating processing by mitochondrial peptidase complexes 1. This process is critical for proper assembly of gatekeeper-containing MCU complexes; loss of MAIP1 function leads to constitutively active channels causing mitochondrial calcium overload and neuronal death in m-AAA protease deficiency 1. Beyond mitochondrial proteostasis, MAIP1 regulates hepatic lipid metabolism. The miR-27b/MAIP1 axis controls lipid accumulation in hepatocytes; MAIP1 overexpression ameliorates miR-27b-induced lipid accumulation, while decreased hepatic MAIP1 expression associates with fatty liver development in high-fat diet models 2. In diabetes pathology, MAIP1 demonstrates anti-apoptotic function through positive epistasis with PFKFB3, promoting survival of dysfunctional β-cells 3. Clinically, MAIP1 emerges as a prognostic biomarker: elevated MAIP1 expression predicts poor outcomes in esophageal cancer through altered tumor immune infiltration 4, and MAIP1 is incorporated into mitochondria-related gene signatures for endometrial cancer prognosis 5. These findings identify MAIP1 as a multifunctional regulator linking mitochondrial calcium homeostasis, metabolic disease, and cancer biology.