POM121C (POM121 transmembrane nucleoporin C) is a component of the nuclear pore complex with dual roles in nuclear transport and metabolic regulation. As a structural nucleoporin, POM121C mediates protein import and RNA export across the nuclear envelope 1. At the molecular level, POM121C interacts with karyopherin-β1 (KPNB1) to facilitate classical cargo nuclear transport 12. The protein contains functionally critical FG-repeats and an α-helix required for nuclear import activity 1. Beyond nuclear transport, POM121C plays an unexpected role in metabolic homeostasis. Adipose tissue expression of POM121C correlates positively with systemic and adipocyte insulin sensitivity, and inversely with lipolysis 3. POM121C knockdown reduces expression of adipocyte-specific markers by 25-50%, indicating necessity for adipogenesis 3. Genome-wide association studies identified POM121C variants linked to fasting insulin levels and growth traits in sheep 34. Clinically, POM121C dysfunction may compromise both nuclear transport and metabolic control. Full-length POM121C enables efficient HIV-1 pre-integration complex nuclear import 1, while N-terminally truncated POM121C inhibits HIV-1 replication by blocking KPNB1-dependent import 2. POM121C phosphorylation patterns show altered frequency in sepsis 5, suggesting potential involvement in inflammatory disease pathogenesis.