Biology subjects

Kanakubo, Y.

Publications and source records attributed to Kanakubo, Y..

2 recordsLinked to original sources

bioRxiv2025

Membrane-enhanced repulsive interactions regulate protein diffusion in cell-size space

Intracellular molecular organization is often explained by attractive interactions driving clustering and phase separation. Although consideration of repulsive forces is essential in physics, their roles remain unclear in cellular contexts. Here, we demonstrated the fundamental role of repulsion in regulating protein diffusion within cell-size space. By analyzing negatively charged protein diffusion in bulk solutions and in cell-size spaces with membranes, we revealed that membrane-enhanced repulsion inhibited protein diffusion in cell-size spaces. This was due to the amplified electrostatic interactions among proteins because of the large membrane area-to-volume ratio. Notably, ATP, a cellular central energy source, further inhibited protein diffusion in cell-size spaces, whereas protein wave propagation on the membrane counteracted this inhibition. These findings suggest an active regulatory mechanism restoring molecular mobility by dynamically adjusting membrane-enhanced repulsive forces. Our study challenges the traditional emphasis on attractive interactions, highlighting repulsion as a critical tunable factor governing molecular transport and spatial organization in cells. TeaserProtein diffusion within crowded cell-size spaces is tuned by membrane-enhanced repulsion and its active regulation.

biophysics↗

bioRxiv2022

Competitive membrane wetting of polymer blends in artificial cells initiates phase separation and promotes fractionation

Biomolecular condensates driven by liquid-liquid phase separation (LLPS) have received attention as novel activity regulators of living organisms. In intracellular LLPS, an important question is what type of biomolecules form condensates under what conditions. In this regard, possible interactions between biomolecules have been investigated. Recently, LLPS condensates have been reported to regulate the membrane structure upon wetting. However, the possibility of membrane wetting, in which the membrane conversely regulates the LLPS, remains unexplored. Using droplets of short polyethylene glycol and long dextran blends encapsulated with a lipid membrane, we demonstrate that membrane wetting regulates LLPS in cell-size spaces and alters the equilibrium state. In smaller droplets, the two-phase region expands beyond the bulk system, and the fractionation degree increases, particularly during the separation between short PEG and long dextran. We explain the space-size dependent LLPS based on the competitive membrane wetting between the polymers. Smaller droplets promote the membrane wetting of short PEG, which enhances the depletion force between long dextran molecules and finally induces LLPS. This shows that competition for membrane wettability among various molecules can regulate LLPS in cell-size spaces, rendering this LLPS principle feasible in living cells.

biophysics↗