SMIM30 is a micropeptide encoded by the lncRNA LINC00998 that functions as a multifaceted regulator of cellular signaling with context-dependent roles in immunity and cancer. In immune contexts, SMIM30 negatively regulates antiviral innate immune responses by disrupting the interaction between MAVS and RIG-I, thereby inhibiting MAVS aggregation and suppressing type I interferon signaling 1. In contrast, SMIM30 promotes hepatocellular carcinoma (HCC) development through multiple mechanisms: it enhances SRC/YES1 membrane anchoring and activates downstream MAPK signaling to promote cell proliferation and migration 2, and it reduces cytosolic calcium levels via SERCA activation to promote G1/S cell cycle transition 3. Beyond cancer, macrophage-expressed SMIM30 maintains adipose tissue insulin sensitivity and systemic metabolic homeostasis by modulating inflammatory responses and macrophage-adipocyte communication 4. Located in endoplasmic reticulum and mitochondrial membranes, SMIM30 represents a novel therapeutic target and biomarker for both metabolic disorders and HCC, with its expression correlating with poor prognosis in HCC patients.