Utilization of extracellular information before ligand-receptor binding reaches equilibrium expands and shifts the input dynamic range

Abstract

Cell signaling systems sense and respond to ligands that bind cell surface receptors. These systems often respond to changes in the concentration of extracellular ligand more rapidly than the ligand equilibrates with its receptor. We demonstrate, by modeling and experiment, a general "systems level" mechanism cells use to take advantage of the information present in the early signal, before receptor binding reaches a new steady state. This mechanism, preequilibrium sensing and signaling (PRESS), operates in signaling systems in which the kinetics of ligand-receptor binding are slower than the downstream signaling steps, and it typically involves transient activation of a downstream step. In the systems where it operates, PRESS expands and shifts the input dynamic range, allowing cells to make different responses to ligand concentrations so high as to be otherwise indistinguishable. Specifically, we show that PRESS applies to the yeast directional polarization in response to pheromone gradients. Consideration of preexisting kinetic data for ligand-receptor interactions suggests that PRESS operates in many cell signaling systems throughout biology. The same mechanism may also operate at other levels in signaling systems in which a slow activation step couples to a faster downstream step. cellular signaling | binding kinetics | dose-response

Ligand Residence Time at G-protein–Coupled Receptors—Why We Should Take Our Time To Study It

“…When concentration-dependent receptor activation was analyzed under nonequilibrium conditions at different time points and in the time range of seconds, it was observed that concentration-effect curves were shifted to higher affinity in a time-dependent manner (Ambrosio and . This phenomenon has also been described in a recent simulation of ligand binding and was predicted to result in a kinetic discrimination between different receptors (Ventura et al, 2014). Earlier work by the group of Jennifer J. Linderman has simulated the impact of different ligand off-rates on receptor signaling and receptor desensitization (Woolf and Linderman, 2003).…”

Single‐cell profiling screen identifies microtubule‐dependent reduction of variability in signaling

“…We constructed strains that expressed Ste5 fused at its C terminus to three tandem copies of YFP (Ste5‐YFP‐ YFP‐YFP, here called Ste5‐YFP). In previous work, we had used this construct to show that, in cells in the G1 phase of the cell cycle, cytosolic Ste5‐YFP translocated to the plasma membrane isotropically within 2–3 min of exposure to isotropic pheromone, followed, after 2–30 min, by clustering of the Ste5‐YFP signal into the signaling site (Fig A; Ventura et al , ). Here, we constructed reference cells that contained this construct, and otherwise isogenic derivatives carrying the ∆ bim1 , ∆ gim4, and tub1‐828 expression perturbations.…”

“…We stimulated reference (“WT”), Tub1‐828 ‐expressing , Δ bim1 and Δ gim4 derivatives of MW003 (bearing three copies of P STE5 ‐STE5‐3xYFP , Ventura et al , ) with 1 μM pheromone and imaged them over time for up to 3.5 h. Single‐cell measurements of Ste5 patch dynamics. Arrows indicate first and second Ste5 patches.…”

“…In this cascade, there are two partially redundant MAP kinases, Fus3 and Kss1, each able to activate downstream steps. After activation, receptors, G‐proteins, and the scaffold concentrate into a membrane patch (Suchkov et al , ; Ventura et al , ; Ismael et al , ) here called the signaling site. The cell converts extracellular ligand concentration into an occupancy measurement (Brent, ) by determining the ratio of ligand‐occupied to unoccupied receptors (Bush et al , ) and transmitting that information accurately, via negative feedback (Yu et al , ) and “push–pull” mechanisms (Andrews et al , ).…”

Testing the limits of gradient sensing

“…The receptor-pheromone binding and unbinding rates determine when this peak difference occurs ( Fig 9 ) [13]. The authors conclude this transient effect is significant enough to improve the gradient sensing ability of yeast cells during mating.…”