TNPO3 (transportin 3) is a nuclear import receptor with dual roles in viral infection and muscular disease. Functionally, TNPO3 mediates nuclear import of diverse cargo through recognition of arginine-serine (SR/RS) repeat-rich and non-classical nuclear localization signals 1. The protein recognizes tyrosine residues within these signals in a phosphorylation-independent manner, with phosphorylation potentially inhibiting binding 1. TNPO3 is critical for HIV-1 infection, facilitating nuclear import of the viral pre-integration complex and enabling nuclear maturation prior to integration 2. Similarly, TNPO3 promotes influenza A virus replication by facilitating viral uncoating and ribonucleoprotein entry into the nucleus 3. During myogenesis, TNPO3 shuttles splicing factor SRSF1 from cytoplasm to nucleus, concentrating in nuclei of differentiated myotubes and regulating alternative splicing necessary for muscle development 4. Pathologically, TNPO3 mutations cause autosomal dominant limb-girdle muscular dystrophy 2 (LGMD D2), with patient muscle biopsies showing aberrant TNPO3 localization, altered SRSF1 expression, and myofibrillar disorganization 56. TNPO3 variants are also associated with antiphospholipid syndrome susceptibility 7. These findings establish TNPO3 as essential for both viral pathogenesis and skeletal muscle homeostasis.