Eukaryotic Gradient Enhancement by Receptor Degradation

Eukaryotic cells can detect the presence of other cells using paracrine signaling. However, what parameters decide a detector cell's ability to identify a beacon cell is poorly understood. Here, we develop a simple model to explore the counterintuitive role of ligand degradation by the detector via receptor endocytosis in sharpening ligand gradients. Using a simple model, we identify a key dimensionless parameter that combines receptor affinity, ligand diffusion, receptor density, and receptor endocytosis rate. We show that in the deterministic regime, increasing degradation always increases gradient sharpness. However, an optimal degradation rate emerges in the noisy regime. Comparison with realistic parameters shows that real detection systems may use receptor degradation to enhance ligand gradients.