The function of PFN4 (profilin family member 4, Ensembl gene identifier ENSG00000176732) is as follows. Involved in male fertility. Required for manchette development and acrosome biogenesis during spermiogenesis (By similarity). Binds in vitro to phospholipids, including phosphatidylinositol 3-phosphate (PtdIns(3)P), phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2), phosphatidylinositol 4-phosphate (PtdIns(4)P) and phosphatidic acid (PA) (PubMed:19419568). Contrary to other profilin family members, does not bind to actin in vitro (PubMed:19419568). {ECO:0000250|UniProtKB:Q9D6I3, ECO:0000269|PubMed:19419568}.