PFN4, also known as profilin 4, is a member of the profilin family. Profilin can be detected in all eukaryotic organisms. It plays an important role in the spatially and temporally controlled growth of actin microfilaments. Profilin is one of the most abundant actin monomer binders, but proteins such as CAP and (in mammals) thymosin β4 have some functional overlaps with profilin. In contrast, ADF/cofilin has some properties that antagonize profilin action. PFN4 also functions in the dynamic turnover and restructuring of the actin cytoskeleton.