A coupled ligand-receptor bulk-surface system on a moving domain: well posedness, regularity and convergence to equilibrium

TL;DR

This paper establishes the mathematical well-posedness, regularity, and long-term behavior of a complex coupled reaction-diffusion system modeling receptor-ligand interactions on moving cellular domains, including new results even without domain movement.

Contribution

It provides the first rigorous analysis of a coupled bulk-surface system with nonlinear interactions and Robin boundary conditions, including existence, uniqueness, regularity, and exponential convergence to equilibrium.

Findings

Proved well-posedness and regularity of the system.

Established exponential convergence to steady state.

Developed new estimates and techniques for nonlinear coupled systems.

Abstract

We prove existence, uniqueness, and regularity for a reaction-diffusion system of coupled bulk-surface equations on a moving domain modelling receptor-ligand dynamics in cells. The nonlinear coupling between the three unknowns is through the Robin boundary condition for the bulk quantity and the right hand sides of the two surface equations. Our results are new even in the non-moving setting, and in this case we also show exponential convergence to a steady state. The primary complications in the analysis are indeed the nonlinear coupling and the Robin boundary condition. For the well posedness and essential boundedness of solutions we use several De Giorgi-type arguments, and we also develop some useful estimates to allow us to apply a Steklov averaging technique for time-dependent operators to prove that solutions are strong. Some of these auxiliary results presented in this paper are of independent interest by themselves.