PACSIN3 (protein kinase C and casein kinase substrate in neurons 3) is a membrane-active scaffolding protein that regulates endocytosis and cytoskeletal organization. Structurally, PACSIN3 contains an N-terminal EFC domain that forms an antiparallel dimer with high affinity for phosphoinositides, enabling membrane tubulation and protein trafficking 1. PACSIN3 plays critical roles in early embryonic development, particularly in notochord formation where it couples directional cell migration with endocytosis and cell specification 1. In mature tissues, PACSIN3 is abundant in muscle where it regulates caveolar biogenesis, creating membrane reservoirs essential for muscle function 2. At the molecular level, PACSIN3 interacts with ADAM12 to enhance ectodomain shedding of heparin-binding EGF-like growth factor 3, and binds TRPV4 calcium channels to inhibit their activation by hypotonic stress and heat 4. Dysregulation of PACSIN3 has clinical significance: mutations are associated with congenital myopathy 27 2, and elevated expression correlates with platinum-resistant epithelial ovarian cancer, where PACSIN3 knockout increases cisplatin-induced apoptosis 5. Recent genomic studies identify PACSIN3 as a novel candidate modifier gene in hypertrophic cardiomyopathy 6, suggesting broader importance in cardiac pathology.