ARPC4 is a core structural subunit of the Arp2/3 complex that mediates actin polymerization and branched actin network formation, driving cell motility 1. Beyond cytoplasmic functions, ARPC4 regulates nuclear actin polymerization to facilitate gene transcription, DNA repair, and homologous recombination of double-strand breaks 2. In cancer biology, ARPC4 promotes metastatic progression through multiple mechanisms: Akt-phosphorylated UFL1 catalyzes ARPC4 UFMylation to enhance lamellipodia formation and cell migration 3, while elevated ARPC4 expression in bladder cancer correlates with lymph node metastasis and cell invasion capacity 4. ARPC4 also functions downstream of mTORC1/mTORC2 signaling in pancreatic cancer, promoting actin-dependent acinar-to-ductal metaplasia and early carcinogenesis 5. Conversely, ARPC4 depletion in epidermis causes psoriasis-like disease through Nrf2 hyperactivation 6, and ARPC4 knockdown impairs CAR T cell resistance in glioblastoma 7. Clinical relevance extends to kidney transplant acute rejection, where ARPC4 serves as a diagnostic biomarker 8. Additionally, bacterial toxins target ARPC4 for ADP-ribosylation to inhibit Arp2/3 complex function 9.