Co-localization and confinement of ecto-nucleotidases modulate extracellular adenosine nucleotide distributions

Area of Science:

• Biochemistry and Molecular Biology
• Cellular Signaling
• Computational Biology

Background:

• Nucleotides are vital signaling molecules in biological systems.
• Adenosine-based nucleotides are degraded by diphosphohydrolases and ecto-nucleotidases (NDAs).
• Nucleotide signaling and degradation are crucial in cellular synapses, forming signaling 'nanodomains' where charged nucleotides interact with membranes and biomolecules.

Purpose of the Study:

• To quantify how electrostatic and steric interactions within synaptic nanodomains control nucleotidase activity kinetics.
• To model the hydrolysis of adenosine triphosphate (ATP) to adenosine monophosphate (AMP) and AMP to adenosine (Ado) by CD39 and CD73.

Main Methods:

• Utilized reaction-diffusion numerical simulations.
• Modeled sequentially-coupled reactions of ATP hydrolysis and AMP dephosphorylation.
• Simulated nucleotidase activity within nanodomain geometries representative of extracellular synapses.

Main Results:

• Nucleotidase confinement reduces reaction rates compared to bulk systems.
• Restricting substrate diffusion accelerates AMP and adenosine formation.
• Nucleotidase co-localization and favorable electrostatic interactions enhance reaction rates, with membrane competition influencing substrate pools.

Conclusions:

• Confinement and electrostatic interactions integratively control nucleotide concentrations and distributions in junctional spaces.
• CD39 and CD73 nucleotidases leverage confinement and electrostatics to precisely regulate nucleotide signaling within synaptic clefts.