Redox-Sensitive Cysteines Confer Proximal Control of the Molecular Crowding Barrier in the Nuclear Pore

The nuclear pore complex forms a highly crowded selective barrier with intrinsically disordered regions at the nuclear membrane to coordinate nucleocytoplasmic molecular communications. Although oxidative stress is known to alter the barrier function, the molecular mechanism underlying this adaptive control of the nuclear pore complex remains unknown. Here we uncover a systematic control of the crowding barrier within the nuclear pore in response to various redox environments. Direct measurements of the crowding states using a crowding-sensitive FRET (Förster resonance energy transfer) probe reveal specific roles of the nuclear pore subunits that adjust the degree of crowding in response to different redox conditions, by adaptively forming or disrupting redox-sensitive disulfide bonds. Relationships between crowding control and the barrier function of the nuclear pore are investigated by single-molecular fluorescence measurements of nuclear transport. Based on these findings, we propose a proximal control model of molecular crowding in vivo that is dynamically regulated at the molecular level.