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 (By similarity). Promotes dimerization of NF-kappa-B subunits and regulates NF-kappa-B transcription factor activity. Promotes growth of cardiomyocytes, but not cardiomyocyte proliferation. Promotes cardiac muscle hypertrophy. Interacts with the heterodimer formed by CAPZA1 and CAPZB (By similarity). Interacts with RELA. At the completion of differentiation and migration of granular cells and at the initiation of the formation of synapses in cerebellar neurons. Belongs to the myotrophin family.