Promotes dimerization of NF-kappa-B subunits and regulates NF-kappa-B transcription factor activity. Plays a role in the regulation of the growth of actin filaments. Inhibits the activity of the F-actin-capping protein complex formed by the CAPZA1 and CAPZB heterodimer. Promotes growth of cardiomyocytes, but not cardiomyocyte proliferation. Promotes cardiac muscle hypertrophy. Belongs to the myotrophin family. Note: This description may include information from UniProtKB.