Inorganic phosphate rapidly switches the stability of Arp2/3-induced actin branches.

Inorganic phosphate increases Arp2/3-induced actin branch stability by 30-fold compared to the ADP state, highlighting Pi as a key regulator of actin network integrity.

• Why it matters: Understanding how nucleotide states influence actin branch stability is crucial for deciphering cellular motility and structural dynamics, yet the specific role of inorganic phosphate remains unclear.
• What they did: The study applied mechanical load to mammalian Arp2/3 complexes in different nucleotide states, revealing rapid Pi exchange (0.2 s-1) and enhanced branch stability when Pi is present, with stable complexes capable of regrowth without ATP reload.
• The result: Findings demonstrate Pi's pivotal role in stabilizing actin branches, enabling persistent network structures and informing potential targets for modulating cell motility and cytoskeletal organization.